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Added xBRZ 1.8 library to source code

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  1. 66 0
      client/xBRZ/Changelog.txt
  2. 621 0
      client/xBRZ/License.txt
  3. 1356 0
      client/xBRZ/xbrz.cpp
  4. 79 0
      client/xBRZ/xbrz.h
  5. 35 0
      client/xBRZ/xbrz_config.h
  6. 266 0
      client/xBRZ/xbrz_tools.h

+ 66 - 0
client/xBRZ/Changelog.txt

@@ -0,0 +1,66 @@
+xBRZ 1.8 [2019-11-28]
+---------------------
+Consider ARGB outside area as transparent
+Fixed ARGB scaling issue on image borders
+
+
+xBRZ 1.7 [2019-07-04]
+---------------------
+Fixed asymmetric color distance
+New parameter: "Center direction bias"
+
+
+xBRZ 1.6 [2018-02-27]
+---------------------
+Added bilinear scaling
+Option to skip color buffer creation
+Updated license info
+
+
+xBRZ 1.5 [2017-08-07]
+---------------------
+Added RGB conversion routines
+
+
+xBRZ 1.4 [2015-07-25]
+---------------------
+Added 6xBRZ scaler
+Create color distance buffer lazily
+
+
+xBRZ 1.3 [2015-04-03]
+---------------------
+Improved ARGB performance by 15%
+Fixed alpha channel gradient bug
+
+
+xBRZ 1.2 [2014-11-21]
+---------------------
+Further improved performance by over 30%
+
+
+xBRZ 1.1 [2014-11-02]
+---------------------
+Support images with alpha channel
+Improved color analysis
+
+
+xBRZ 1.0 [2013-02-11]
+---------------------
+Fixed xBRZ scaler compiler issues for GCC
+
+ 
+xBRZ 0.2 [2012-12-11]
+---------------------
+Added 5xBRZ scaler
+Optimized xBRZ scaler performance by factor 3
+Further improved image quality of xBRZ scaler
+
+
+xBRZ 0.1 [2012-09-26]
+---------------------
+Initial release:
+- scale while preserving small image features
+- support multithreading
+- support 64-bit architectures
+- support processing image slices

+ 621 - 0
client/xBRZ/License.txt

@@ -0,0 +1,621 @@
+                    GNU GENERAL PUBLIC LICENSE
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+the Program, the only way you could satisfy both those terms and this
+License would be to refrain entirely from conveying the Program.
+
+  13. Use with the GNU Affero General Public License.
+
+  Notwithstanding any other provision of this License, you have
+permission to link or combine any covered work with a work licensed
+under version 3 of the GNU Affero General Public License into a single
+combined work, and to convey the resulting work.  The terms of this
+License will continue to apply to the part which is the covered work,
+but the special requirements of the GNU Affero General Public License,
+section 13, concerning interaction through a network will apply to the
+combination as such.
+
+  14. Revised Versions of this License.
+
+  The Free Software Foundation may publish revised and/or new versions of
+the GNU General Public License from time to time.  Such new versions will
+be similar in spirit to the present version, but may differ in detail to
+address new problems or concerns.
+
+  Each version is given a distinguishing version number.  If the
+Program specifies that a certain numbered version of the GNU General
+Public License "or any later version" applies to it, you have the
+option of following the terms and conditions either of that numbered
+version or of any later version published by the Free Software
+Foundation.  If the Program does not specify a version number of the
+GNU General Public License, you may choose any version ever published
+by the Free Software Foundation.
+
+  If the Program specifies that a proxy can decide which future
+versions of the GNU General Public License can be used, that proxy's
+public statement of acceptance of a version permanently authorizes you
+to choose that version for the Program.
+
+  Later license versions may give you additional or different
+permissions.  However, no additional obligations are imposed on any
+author or copyright holder as a result of your choosing to follow a
+later version.
+
+  15. Disclaimer of Warranty.
+
+  THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
+APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
+HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
+OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
+THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
+IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
+ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
+
+  16. Limitation of Liability.
+
+  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
+THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
+GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
+USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
+DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
+PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
+EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGES.
+
+  17. Interpretation of Sections 15 and 16.
+
+  If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+                     END OF TERMS AND CONDITIONS

+ 1356 - 0
client/xBRZ/xbrz.cpp

@@ -0,0 +1,1356 @@
+// ****************************************************************************
+// * This file is part of the xBRZ project. It is distributed under           *
+// * GNU General Public License: https://www.gnu.org/licenses/gpl-3.0         *
+// * Copyright (C) Zenju (zenju AT gmx DOT de) - All Rights Reserved          *
+// *                                                                          *
+// * Additionally and as a special exception, the author gives permission     *
+// * to link the code of this program with the following libraries            *
+// * (or with modified versions that use the same licenses), and distribute   *
+// * linked combinations including the two: MAME, FreeFileSync, Snes9x, ePSXe *
+// * You must obey the GNU General Public License in all respects for all of  *
+// * the code used other than MAME, FreeFileSync, Snes9x, ePSXe.              *
+// * If you modify this file, you may extend this exception to your version   *
+// * of the file, but you are not obligated to do so. If you do not wish to   *
+// * do so, delete this exception statement from your version.                *
+// ****************************************************************************
+
+#include "xbrz.h"
+#include <cassert>
+#include <vector>
+#include <algorithm>
+#include <cmath> //std::sqrt
+#include "xbrz_tools.h"
+
+using namespace xbrz;
+
+
+namespace
+{
+template <unsigned int M, unsigned int N> inline
+uint32_t gradientRGB(uint32_t pixFront, uint32_t pixBack) //blend front color with opacity M / N over opaque background: https://en.wikipedia.org/wiki/Alpha_compositing#Alpha_blending
+{
+    static_assert(0 < M && M < N && N <= 1000);
+
+    auto calcColor = [](unsigned char colFront, unsigned char colBack) -> unsigned char { return (colFront * M + colBack * (N - M)) / N; };
+
+    return makePixel(calcColor(getRed  (pixFront), getRed  (pixBack)),
+                     calcColor(getGreen(pixFront), getGreen(pixBack)),
+                     calcColor(getBlue (pixFront), getBlue (pixBack)));
+}
+
+
+template <unsigned int M, unsigned int N> inline
+uint32_t gradientARGB(uint32_t pixFront, uint32_t pixBack) //find intermediate color between two colors with alpha channels (=> NO alpha blending!!!)
+{
+    static_assert(0 < M && M < N && N <= 1000);
+
+    const unsigned int weightFront = getAlpha(pixFront) * M;
+    const unsigned int weightBack  = getAlpha(pixBack) * (N - M);
+    const unsigned int weightSum   = weightFront + weightBack;
+    if (weightSum == 0)
+        return 0;
+
+    auto calcColor = [=](unsigned char colFront, unsigned char colBack)
+    {
+        return static_cast<unsigned char>((colFront * weightFront + colBack * weightBack) / weightSum);
+    };
+
+    return makePixel(static_cast<unsigned char>(weightSum / N),
+                     calcColor(getRed  (pixFront), getRed  (pixBack)),
+                     calcColor(getGreen(pixFront), getGreen(pixBack)),
+                     calcColor(getBlue (pixFront), getBlue (pixBack)));
+}
+
+
+//inline
+//double fastSqrt(double n)
+//{
+//    __asm //speeds up xBRZ by about 9% compared to std::sqrt which internally uses the same assembler instructions but adds some "fluff"
+//    {
+//        fld n
+//        fsqrt
+//    }
+//}
+//
+
+
+#ifdef _MSC_VER
+    #define FORCE_INLINE __forceinline
+#elif defined __GNUC__
+    #define FORCE_INLINE __attribute__((always_inline)) inline
+#else
+    #define FORCE_INLINE inline
+#endif
+
+
+enum RotationDegree //clock-wise
+{
+    ROT_0,
+    ROT_90,
+    ROT_180,
+    ROT_270
+};
+
+//calculate input matrix coordinates after rotation at compile time
+template <RotationDegree rotDeg, size_t I, size_t J, size_t N>
+struct MatrixRotation;
+
+template <size_t I, size_t J, size_t N>
+struct MatrixRotation<ROT_0, I, J, N>
+{
+    static const size_t I_old = I;
+    static const size_t J_old = J;
+};
+
+template <RotationDegree rotDeg, size_t I, size_t J, size_t N> //(i, j) = (row, col) indices, N = size of (square) matrix
+struct MatrixRotation
+{
+    static const size_t I_old = N - 1 - MatrixRotation<static_cast<RotationDegree>(rotDeg - 1), I, J, N>::J_old; //old coordinates before rotation!
+    static const size_t J_old =         MatrixRotation<static_cast<RotationDegree>(rotDeg - 1), I, J, N>::I_old; //
+};
+
+
+template <size_t N, RotationDegree rotDeg>
+class OutputMatrix
+{
+public:
+    OutputMatrix(uint32_t* out, int outWidth) : //access matrix area, top-left at position "out" for image with given width
+        out_(out),
+        outWidth_(outWidth) {}
+
+    template <size_t I, size_t J>
+    uint32_t& ref() const
+    {
+        static const size_t I_old = MatrixRotation<rotDeg, I, J, N>::I_old;
+        static const size_t J_old = MatrixRotation<rotDeg, I, J, N>::J_old;
+        return *(out_ + J_old + I_old * outWidth_);
+    }
+
+private:
+    uint32_t* out_;
+    const int outWidth_;
+};
+
+
+template <class T> inline
+T square(T value) { return value * value; }
+
+
+#if 0
+inline
+double distRGB(uint32_t pix1, uint32_t pix2)
+{
+    const double r_diff = static_cast<int>(getRed  (pix1)) - getRed  (pix2);
+    const double g_diff = static_cast<int>(getGreen(pix1)) - getGreen(pix2);
+    const double b_diff = static_cast<int>(getBlue (pix1)) - getBlue (pix2);
+
+    //euklidean RGB distance
+    return std::sqrt(square(r_diff) + square(g_diff) + square(b_diff));
+}
+#endif
+
+
+inline
+double distYCbCr(uint32_t pix1, uint32_t pix2, double lumaWeight)
+{
+    //https://en.wikipedia.org/wiki/YCbCr#ITU-R_BT.601_conversion
+    //YCbCr conversion is a matrix multiplication => take advantage of linearity by subtracting first!
+    const int r_diff = static_cast<int>(getRed  (pix1)) - getRed  (pix2); //we may delay division by 255 to after matrix multiplication
+    const int g_diff = static_cast<int>(getGreen(pix1)) - getGreen(pix2); //
+    const int b_diff = static_cast<int>(getBlue (pix1)) - getBlue (pix2); //substraction for int is noticeable faster than for double!
+
+    //const double k_b = 0.0722; //ITU-R BT.709 conversion
+    //const double k_r = 0.2126; //
+    const double k_b = 0.0593; //ITU-R BT.2020 conversion
+    const double k_r = 0.2627; //
+    const double k_g = 1 - k_b - k_r;
+
+    const double scale_b = 0.5 / (1 - k_b);
+    const double scale_r = 0.5 / (1 - k_r);
+
+    const double y   = k_r * r_diff + k_g * g_diff + k_b * b_diff; //[!], analog YCbCr!
+    const double c_b = scale_b * (b_diff - y);
+    const double c_r = scale_r * (r_diff - y);
+
+    //we skip division by 255 to have similar range like other distance functions
+    return std::sqrt(square(lumaWeight * y) + square(c_b) + square(c_r));
+}
+
+
+inline
+double distYCbCrBuffered(uint32_t pix1, uint32_t pix2)
+{
+    //30% perf boost compared to plain distYCbCr()!
+    //consumes 64 MB memory; using double is only 2% faster, but takes 128 MB
+    static const std::vector<float> diffToDist = []
+    {
+        std::vector<float> tmp;
+
+        for (uint32_t i = 0; i < 256 * 256 * 256; ++i) //startup time: 114 ms on Intel Core i5 (four cores)
+        {
+            const int r_diff = static_cast<signed char>(getByte<2>(i)) * 2;
+            const int g_diff = static_cast<signed char>(getByte<1>(i)) * 2;
+            const int b_diff = static_cast<signed char>(getByte<0>(i)) * 2;
+
+            const double k_b = 0.0593; //ITU-R BT.2020 conversion
+            const double k_r = 0.2627; //
+            const double k_g = 1 - k_b - k_r;
+
+            const double scale_b = 0.5 / (1 - k_b);
+            const double scale_r = 0.5 / (1 - k_r);
+
+            const double y   = k_r * r_diff + k_g * g_diff + k_b * b_diff; //[!], analog YCbCr!
+            const double c_b = scale_b * (b_diff - y);
+            const double c_r = scale_r * (r_diff - y);
+
+            tmp.push_back(static_cast<float>(std::sqrt(square(y) + square(c_b) + square(c_r))));
+        }
+        return tmp;
+    }();
+
+    //if (pix1 == pix2) -> 8% perf degradation!
+    //    return 0;
+    //if (pix1 < pix2)
+    //    std::swap(pix1, pix2); -> 30% perf degradation!!!
+
+    const int r_diff = static_cast<int>(getRed  (pix1)) - getRed  (pix2);
+    const int g_diff = static_cast<int>(getGreen(pix1)) - getGreen(pix2);
+    const int b_diff = static_cast<int>(getBlue (pix1)) - getBlue (pix2);
+
+    const size_t index = (static_cast<unsigned char>(r_diff / 2) << 16) | //slightly reduce precision (division by 2) to squeeze value into single byte
+                         (static_cast<unsigned char>(g_diff / 2) <<  8) |
+                         (static_cast<unsigned char>(b_diff / 2));
+
+#if 0 //attention: the following calculation creates an asymmetric color distance!!! (e.g. r_diff=46 will be unpacked as 45, but r_diff=-46 unpacks to -47
+    const size_t index = (((r_diff + 0xFF) / 2) << 16) | //slightly reduce precision (division by 2) to squeeze value into single byte
+                         (((g_diff + 0xFF) / 2) <<  8) |
+                         (( b_diff + 0xFF) / 2);
+#endif
+    return diffToDist[index];
+}
+
+
+#if defined _MSC_VER && !defined NDEBUG
+    const int debugPixelX = -1;
+    const int debugPixelY = 58;
+
+    thread_local bool breakIntoDebugger = false;
+#endif
+
+
+enum BlendType
+{
+    BLEND_NONE = 0,
+    BLEND_NORMAL,   //a normal indication to blend
+    BLEND_DOMINANT, //a strong indication to blend
+    //attention: BlendType must fit into the value range of 2 bit!!!
+};
+
+struct BlendResult
+{
+    BlendType
+    /**/blend_f, blend_g,
+    /**/blend_j, blend_k;
+};
+
+
+struct Kernel_3x3
+{
+    uint32_t
+    a, b, c,
+    d, e, f,
+    g, h, i;
+};
+
+struct Kernel_4x4 //kernel for preprocessing step
+{
+    uint32_t
+    a, b, c, //
+    e, f, g, // support reinterpret_cast from Kernel_4x4 => Kernel_3x3
+    i, j, k, //
+    m, n, o,
+    d, h, l, p;
+};
+
+/* input kernel area naming convention:
+-----------------
+| A | B | C | D |
+|---|---|---|---|
+| E | F | G | H |   evaluate the four corners between F, G, J, K
+|---|---|---|---|   input pixel is at position F
+| I | J | K | L |
+|---|---|---|---|
+| M | N | O | P |
+-----------------
+*/
+template <class ColorDistance>
+FORCE_INLINE //detect blend direction
+BlendResult preProcessCorners(const Kernel_4x4& ker, const xbrz::ScalerCfg& cfg) //result: F, G, J, K corners of "GradientType"
+{
+#if defined _MSC_VER && !defined NDEBUG
+    if (breakIntoDebugger)
+        __debugbreak(); //__asm int 3;
+#endif
+
+    BlendResult result = {};
+
+    if ((ker.f == ker.g &&
+         ker.j == ker.k) ||
+        (ker.f == ker.j &&
+         ker.g == ker.k))
+        return result;
+
+    auto dist = [&](uint32_t pix1, uint32_t pix2) { return ColorDistance::dist(pix1, pix2, cfg.luminanceWeight); };
+
+    double jg = dist(ker.i, ker.f) + dist(ker.f, ker.c) + dist(ker.n, ker.k) + dist(ker.k, ker.h) + cfg.centerDirectionBias * dist(ker.j, ker.g);
+    double fk = dist(ker.e, ker.j) + dist(ker.j, ker.o) + dist(ker.b, ker.g) + dist(ker.g, ker.l) + cfg.centerDirectionBias * dist(ker.f, ker.k);
+
+    if (jg < fk) //test sample: 70% of values max(jg, fk) / min(jg, fk) are between 1.1 and 3.7 with median being 1.8
+    {
+        const bool dominantGradient = cfg.dominantDirectionThreshold * jg < fk;
+        if (ker.f != ker.g && ker.f != ker.j)
+            result.blend_f = dominantGradient ? BLEND_DOMINANT : BLEND_NORMAL;
+
+        if (ker.k != ker.j && ker.k != ker.g)
+            result.blend_k = dominantGradient ? BLEND_DOMINANT : BLEND_NORMAL;
+    }
+    else if (fk < jg)
+    {
+        const bool dominantGradient = cfg.dominantDirectionThreshold * fk < jg;
+        if (ker.j != ker.f && ker.j != ker.k)
+            result.blend_j = dominantGradient ? BLEND_DOMINANT : BLEND_NORMAL;
+
+        if (ker.g != ker.f && ker.g != ker.k)
+            result.blend_g = dominantGradient ? BLEND_DOMINANT : BLEND_NORMAL;
+    }
+    return result;
+}
+
+#define DEF_GETTER(x) template <RotationDegree rotDeg> uint32_t inline get_##x(const Kernel_3x3& ker) { return ker.x; }
+//we cannot and NEED NOT write "ker.##x" since ## concatenates preprocessor tokens but "." is not a token
+DEF_GETTER(a) DEF_GETTER(b) DEF_GETTER(c)
+DEF_GETTER(d) DEF_GETTER(e) DEF_GETTER(f)
+DEF_GETTER(g) DEF_GETTER(h) DEF_GETTER(i)
+#undef DEF_GETTER
+
+#define DEF_GETTER(x, y) template <> inline uint32_t get_##x<ROT_90>(const Kernel_3x3& ker) { return ker.y; }
+DEF_GETTER(a, g) DEF_GETTER(b, d) DEF_GETTER(c, a)
+DEF_GETTER(d, h) DEF_GETTER(e, e) DEF_GETTER(f, b)
+DEF_GETTER(g, i) DEF_GETTER(h, f) DEF_GETTER(i, c)
+#undef DEF_GETTER
+
+#define DEF_GETTER(x, y) template <> inline uint32_t get_##x<ROT_180>(const Kernel_3x3& ker) { return ker.y; }
+DEF_GETTER(a, i) DEF_GETTER(b, h) DEF_GETTER(c, g)
+DEF_GETTER(d, f) DEF_GETTER(e, e) DEF_GETTER(f, d)
+DEF_GETTER(g, c) DEF_GETTER(h, b) DEF_GETTER(i, a)
+#undef DEF_GETTER
+
+#define DEF_GETTER(x, y) template <> inline uint32_t get_##x<ROT_270>(const Kernel_3x3& ker) { return ker.y; }
+DEF_GETTER(a, c) DEF_GETTER(b, f) DEF_GETTER(c, i)
+DEF_GETTER(d, b) DEF_GETTER(e, e) DEF_GETTER(f, h)
+DEF_GETTER(g, a) DEF_GETTER(h, d) DEF_GETTER(i, g)
+#undef DEF_GETTER
+
+
+//compress four blend types into a single byte
+//inline BlendType getTopL   (unsigned char b) { return static_cast<BlendType>(0x3 & b); }
+inline BlendType getTopR   (unsigned char b) { return static_cast<BlendType>(0x3 & (b >> 2)); }
+inline BlendType getBottomR(unsigned char b) { return static_cast<BlendType>(0x3 & (b >> 4)); }
+inline BlendType getBottomL(unsigned char b) { return static_cast<BlendType>(0x3 & (b >> 6)); }
+
+inline void clearAddTopL(unsigned char& b, BlendType bt) { b = static_cast<unsigned char>(bt); }
+inline void addTopR     (unsigned char& b, BlendType bt) { b |= (bt << 2); } //buffer is assumed to be initialized before preprocessing!
+inline void addBottomR  (unsigned char& b, BlendType bt) { b |= (bt << 4); } //e.g. via clearAddTopL()
+inline void addBottomL  (unsigned char& b, BlendType bt) { b |= (bt << 6); } //
+
+inline bool blendingNeeded(unsigned char b)
+{
+    static_assert(BLEND_NONE == 0);
+    return b != 0;
+}
+
+template <RotationDegree rotDeg> inline
+unsigned char rotateBlendInfo(unsigned char b) { return b; }
+template <> inline unsigned char rotateBlendInfo<ROT_90 >(unsigned char b) { return ((b << 2) | (b >> 6)) & 0xff; }
+template <> inline unsigned char rotateBlendInfo<ROT_180>(unsigned char b) { return ((b << 4) | (b >> 4)) & 0xff; }
+template <> inline unsigned char rotateBlendInfo<ROT_270>(unsigned char b) { return ((b << 6) | (b >> 2)) & 0xff; }
+
+
+/* input kernel area naming convention:
+-------------
+| A | B | C |
+|---|---|---|
+| D | E | F | input pixel is at position E
+|---|---|---|
+| G | H | I |
+-------------
+*/
+template <class Scaler, class ColorDistance, RotationDegree rotDeg>
+FORCE_INLINE //perf: quite worth it!
+void blendPixel(const Kernel_3x3& ker,
+                uint32_t* target, int trgWidth,
+                unsigned char blendInfo, //result of preprocessing all four corners of pixel "e"
+                const xbrz::ScalerCfg& cfg)
+{
+    //#define a get_a<rotDeg>(ker)
+#define b get_b<rotDeg>(ker)
+#define c get_c<rotDeg>(ker)
+#define d get_d<rotDeg>(ker)
+#define e get_e<rotDeg>(ker)
+#define f get_f<rotDeg>(ker)
+#define g get_g<rotDeg>(ker)
+#define h get_h<rotDeg>(ker)
+#define i get_i<rotDeg>(ker)
+
+#if defined _MSC_VER && !defined NDEBUG
+    if (breakIntoDebugger)
+        __debugbreak(); //__asm int 3;
+#endif
+
+    const unsigned char blend = rotateBlendInfo<rotDeg>(blendInfo);
+
+    if (getBottomR(blend) >= BLEND_NORMAL)
+    {
+        auto eq   = [&](uint32_t pix1, uint32_t pix2) { return ColorDistance::dist(pix1, pix2, cfg.luminanceWeight) < cfg.equalColorTolerance; };
+        auto dist = [&](uint32_t pix1, uint32_t pix2) { return ColorDistance::dist(pix1, pix2, cfg.luminanceWeight); };
+
+        const bool doLineBlend = [&]() -> bool
+        {
+            if (getBottomR(blend) >= BLEND_DOMINANT)
+                return true;
+
+            //make sure there is no second blending in an adjacent rotation for this pixel: handles insular pixels, mario eyes
+            if (getTopR(blend) != BLEND_NONE && !eq(e, g)) //but support double-blending for 90° corners
+                return false;
+            if (getBottomL(blend) != BLEND_NONE && !eq(e, c))
+                return false;
+
+            //no full blending for L-shapes; blend corner only (handles "mario mushroom eyes")
+            if (!eq(e, i) && eq(g, h) && eq(h, i) && eq(i, f) && eq(f, c))
+                return false;
+
+            return true;
+        }();
+
+        const uint32_t px = dist(e, f) <= dist(e, h) ? f : h; //choose most similar color
+
+        OutputMatrix<Scaler::scale, rotDeg> out(target, trgWidth);
+
+        if (doLineBlend)
+        {
+            const double fg = dist(f, g); //test sample: 70% of values max(fg, hc) / min(fg, hc) are between 1.1 and 3.7 with median being 1.9
+            const double hc = dist(h, c); //
+
+            const bool haveShallowLine = cfg.steepDirectionThreshold * fg <= hc && e != g && d != g;
+            const bool haveSteepLine   = cfg.steepDirectionThreshold * hc <= fg && e != c && b != c;
+
+            if (haveShallowLine)
+            {
+                if (haveSteepLine)
+                    Scaler::blendLineSteepAndShallow(px, out);
+                else
+                    Scaler::blendLineShallow(px, out);
+            }
+            else
+            {
+                if (haveSteepLine)
+                    Scaler::blendLineSteep(px, out);
+                else
+                    Scaler::blendLineDiagonal(px, out);
+            }
+        }
+        else
+            Scaler::blendCorner(px, out);
+    }
+
+    //#undef a
+#undef b
+#undef c
+#undef d
+#undef e
+#undef f
+#undef g
+#undef h
+#undef i
+}
+
+
+class OobReaderTransparent
+{
+public:
+    OobReaderTransparent(const uint32_t* src, int srcWidth, int srcHeight, int y) :
+        s_m1(0 <= y - 1 && y - 1 < srcHeight ? src + srcWidth * (y - 1) : nullptr),
+        s_0 (0 <= y     && y     < srcHeight ? src + srcWidth *  y      : nullptr),
+        s_p1(0 <= y + 1 && y + 1 < srcHeight ? src + srcWidth * (y + 1) : nullptr),
+        s_p2(0 <= y + 2 && y + 2 < srcHeight ? src + srcWidth * (y + 2) : nullptr),
+        srcWidth_(srcWidth) {}
+
+    void readDhlp(Kernel_4x4& ker, int x) const //(x, y) is at kernel position F
+    {
+        [[likely]] if (const int x_p2 = x + 2; 0 <= x_p2 && x_p2 < srcWidth_)
+        {
+            ker.d = s_m1 ? s_m1[x_p2] : 0;
+            ker.h = s_0  ? s_0 [x_p2] : 0;
+            ker.l = s_p1 ? s_p1[x_p2] : 0;
+            ker.p = s_p2 ? s_p2[x_p2] : 0;
+        }
+        else
+        {
+            ker.d = 0;
+            ker.h = 0;
+            ker.l = 0;
+            ker.p = 0;
+        }
+    }
+
+private:
+    const uint32_t* const s_m1;
+    const uint32_t* const s_0;
+    const uint32_t* const s_p1;
+    const uint32_t* const s_p2;
+    const int srcWidth_;
+};
+
+
+class OobReaderDuplicate
+{
+public:
+    OobReaderDuplicate(const uint32_t* src, int srcWidth, int srcHeight, int y) :
+        s_m1(src + srcWidth * std::clamp(y - 1, 0, srcHeight - 1)),
+        s_0 (src + srcWidth * std::clamp(y,     0, srcHeight - 1)),
+        s_p1(src + srcWidth * std::clamp(y + 1, 0, srcHeight - 1)),
+        s_p2(src + srcWidth * std::clamp(y + 2, 0, srcHeight - 1)),
+        srcWidth_(srcWidth) {}
+
+    void readDhlp(Kernel_4x4& ker, int x) const //(x, y) is at kernel position F
+    {
+        const int x_p2 = std::clamp(x + 2, 0, srcWidth_ - 1);
+        ker.d = s_m1[x_p2];
+        ker.h = s_0 [x_p2];
+        ker.l = s_p1[x_p2];
+        ker.p = s_p2[x_p2];
+    }
+
+private:
+    const uint32_t* const s_m1;
+    const uint32_t* const s_0;
+    const uint32_t* const s_p1;
+    const uint32_t* const s_p2;
+    const int srcWidth_;
+};
+
+
+template <class Scaler, class ColorDistance, class OobReader> //scaler policy: see "Scaler2x" reference implementation
+void scaleImage(const uint32_t* src, uint32_t* trg, int srcWidth, int srcHeight, const xbrz::ScalerCfg& cfg, int yFirst, int yLast)
+{
+    yFirst = std::max(yFirst, 0);
+    yLast  = std::min(yLast, srcHeight);
+    if (yFirst >= yLast || srcWidth <= 0)
+        return;
+
+    const int trgWidth = srcWidth * Scaler::scale;
+
+    //(ab)use space of "sizeof(uint32_t) * srcWidth * Scaler::scale" at the end of the image as temporary
+    //buffer for "on the fly preprocessing" without risk of accidental overwriting before accessing
+    unsigned char* const preProcBuf = reinterpret_cast<unsigned char*>(trg + yLast * Scaler::scale * trgWidth) - srcWidth;
+
+    //initialize preprocessing buffer for first row of current stripe: detect upper left and right corner blending
+    //this cannot be optimized for adjacent processing stripes; we must not allow for a memory race condition!
+    {
+        const OobReader oobReader(src, srcWidth, srcHeight, yFirst - 1);
+
+        //initialize at position x = -1
+        Kernel_4x4 ker4 = {};
+        oobReader.readDhlp(ker4, -4); //hack: read a, e, i, m at x = -1
+        ker4.a = ker4.d;
+        ker4.e = ker4.h;
+        ker4.i = ker4.l;
+        ker4.m = ker4.p;
+
+        oobReader.readDhlp(ker4, -3);
+        ker4.b = ker4.d;
+        ker4.f = ker4.h;
+        ker4.j = ker4.l;
+        ker4.n = ker4.p;
+
+        oobReader.readDhlp(ker4, -2);
+        ker4.c = ker4.d;
+        ker4.g = ker4.h;
+        ker4.k = ker4.l;
+        ker4.o = ker4.p;
+
+        oobReader.readDhlp(ker4, -1);
+
+        {
+            const BlendResult res = preProcessCorners<ColorDistance>(ker4, cfg);
+            clearAddTopL(preProcBuf[0], res.blend_k); //set 1st known corner for (0, yFirst)
+        }
+
+        for (int x = 0; x < srcWidth; ++x)
+        {
+            ker4.a = ker4.b;    //shift previous kernel to the left
+            ker4.e = ker4.f;    // -----------------
+            ker4.i = ker4.j;    // | A | B | C | D |
+            ker4.m = ker4.n;    // |---|---|---|---|
+            /**/                // | E | F | G | H | (x, yFirst - 1) is at position F
+            ker4.b = ker4.c;    // |---|---|---|---|
+            ker4.f = ker4.g;    // | I | J | K | L |
+            ker4.j = ker4.k;    // |---|---|---|---|
+            ker4.n = ker4.o;    // | M | N | O | P |
+            /**/                // -----------------
+            ker4.c = ker4.d;
+            ker4.g = ker4.h;
+            ker4.k = ker4.l;
+            ker4.o = ker4.p;
+
+            oobReader.readDhlp(ker4, x);
+
+            /*  preprocessing blend result:
+                ---------
+                | F | G |   evaluate corner between F, G, J, K
+                |---+---|   current input pixel is at position F
+                | J | K |
+                ---------                                        */
+            const BlendResult res = preProcessCorners<ColorDistance>(ker4, cfg);
+            addTopR(preProcBuf[x], res.blend_j); //set 2nd known corner for (x, yFirst)
+
+            if (x + 1 < srcWidth)
+                clearAddTopL(preProcBuf[x + 1], res.blend_k); //set 1st known corner for (x + 1, yFirst)
+        }
+    }
+    //------------------------------------------------------------------------------------
+
+    for (int y = yFirst; y < yLast; ++y)
+    {
+        uint32_t* out = trg + Scaler::scale * y * trgWidth; //consider MT "striped" access
+
+        const OobReader oobReader(src, srcWidth, srcHeight, y);
+
+        //initialize at position x = -1
+        Kernel_4x4 ker4 = {};
+        oobReader.readDhlp(ker4, -4); //hack: read a, e, i, m at x = -1
+        ker4.a = ker4.d;
+        ker4.e = ker4.h;
+        ker4.i = ker4.l;
+        ker4.m = ker4.p;
+
+        oobReader.readDhlp(ker4, -3);
+        ker4.b = ker4.d;
+        ker4.f = ker4.h;
+        ker4.j = ker4.l;
+        ker4.n = ker4.p;
+
+        oobReader.readDhlp(ker4, -2);
+        ker4.c = ker4.d;
+        ker4.g = ker4.h;
+        ker4.k = ker4.l;
+        ker4.o = ker4.p;
+
+        oobReader.readDhlp(ker4, -1);
+
+        unsigned char blend_xy1 = 0; //corner blending for current (x, y + 1) position
+        {
+            const BlendResult res = preProcessCorners<ColorDistance>(ker4, cfg);
+            clearAddTopL(blend_xy1, res.blend_k); //set 1st known corner for (0, y + 1) and buffer for use on next column
+
+            addBottomL(preProcBuf[0], res.blend_g); //set 3rd known corner for (0, y)
+        }
+
+        for (int x = 0; x < srcWidth; ++x, out += Scaler::scale)
+        {
+#if defined _MSC_VER && !defined NDEBUG
+            breakIntoDebugger = debugPixelX == x && debugPixelY == y;
+#endif
+            ker4.a = ker4.b;    //shift previous kernel to the left
+            ker4.e = ker4.f;    // -----------------
+            ker4.i = ker4.j;    // | A | B | C | D |
+            ker4.m = ker4.n;    // |---|---|---|---|
+            /**/                // | E | F | G | H | (x, y) is at position F
+            ker4.b = ker4.c;    // |---|---|---|---|
+            ker4.f = ker4.g;    // | I | J | K | L |
+            ker4.j = ker4.k;    // |---|---|---|---|
+            ker4.n = ker4.o;    // | M | N | O | P |
+            /**/                // -----------------
+            ker4.c = ker4.d;
+            ker4.g = ker4.h;
+            ker4.k = ker4.l;
+            ker4.o = ker4.p;
+
+            oobReader.readDhlp(ker4, x);
+
+            //evaluate the four corners on bottom-right of current pixel
+            unsigned char blend_xy = preProcBuf[x]; //for current (x, y) position
+            {
+                /*  preprocessing blend result:
+                    ---------
+                    | F | G |   evaluate corner between F, G, J, K
+                    |---+---|   current input pixel is at position F
+                    | J | K |
+                    ---------                                        */
+                const BlendResult res = preProcessCorners<ColorDistance>(ker4, cfg);
+                addBottomR(blend_xy, res.blend_f); //all four corners of (x, y) have been determined at this point due to processing sequence!
+
+                addTopR(blend_xy1, res.blend_j); //set 2nd known corner for (x, y + 1)
+                preProcBuf[x] = blend_xy1; //store on current buffer position for use on next row
+
+                [[likely]] if (x + 1 < srcWidth)
+                {
+                    //blend_xy1 -> blend_x1y1
+                    clearAddTopL(blend_xy1, res.blend_k); //set 1st known corner for (x + 1, y + 1) and buffer for use on next column
+
+                    addBottomL(preProcBuf[x + 1], res.blend_g); //set 3rd known corner for (x + 1, y)
+                }
+            }
+
+            //fill block of size scale * scale with the given color
+            fillBlock(out, trgWidth * sizeof(uint32_t), ker4.f, Scaler::scale, Scaler::scale);
+            //place *after* preprocessing step, to not overwrite the results while processing the last pixel!
+
+            //blend all four corners of current pixel
+            if (blendingNeeded(blend_xy))
+            {
+                const auto& ker3 = reinterpret_cast<const Kernel_3x3&>(ker4); //"The Things We Do for Perf"
+                blendPixel<Scaler, ColorDistance, ROT_0  >(ker3, out, trgWidth, blend_xy, cfg);
+                blendPixel<Scaler, ColorDistance, ROT_90 >(ker3, out, trgWidth, blend_xy, cfg);
+                blendPixel<Scaler, ColorDistance, ROT_180>(ker3, out, trgWidth, blend_xy, cfg);
+                blendPixel<Scaler, ColorDistance, ROT_270>(ker3, out, trgWidth, blend_xy, cfg);
+            }
+        }
+    }
+}
+
+//------------------------------------------------------------------------------------
+
+template <class ColorGradient>
+struct Scaler2x : public ColorGradient
+{
+    static const int scale = 2;
+
+    template <unsigned int M, unsigned int N> //bring template function into scope for GCC
+    static void alphaGrad(uint32_t& pixBack, uint32_t pixFront) { ColorGradient::template alphaGrad<M, N>(pixBack, pixFront); }
+
+
+    template <class OutputMatrix>
+    static void blendLineShallow(uint32_t col, OutputMatrix& out)
+    {
+        alphaGrad<1, 4>(out.template ref<scale - 1, 0>(), col);
+        alphaGrad<3, 4>(out.template ref<scale - 1, 1>(), col);
+    }
+
+    template <class OutputMatrix>
+    static void blendLineSteep(uint32_t col, OutputMatrix& out)
+    {
+        alphaGrad<1, 4>(out.template ref<0, scale - 1>(), col);
+        alphaGrad<3, 4>(out.template ref<1, scale - 1>(), col);
+    }
+
+    template <class OutputMatrix>
+    static void blendLineSteepAndShallow(uint32_t col, OutputMatrix& out)
+    {
+        alphaGrad<1, 4>(out.template ref<1, 0>(), col);
+        alphaGrad<1, 4>(out.template ref<0, 1>(), col);
+        alphaGrad<5, 6>(out.template ref<1, 1>(), col); //[!] fixes 7/8 used in xBR
+    }
+
+    template <class OutputMatrix>
+    static void blendLineDiagonal(uint32_t col, OutputMatrix& out)
+    {
+        alphaGrad<1, 2>(out.template ref<1, 1>(), col);
+    }
+
+    template <class OutputMatrix>
+    static void blendCorner(uint32_t col, OutputMatrix& out)
+    {
+        //model a round corner
+        alphaGrad<21, 100>(out.template ref<1, 1>(), col); //exact: 1 - pi/4 = 0.2146018366
+    }
+};
+
+
+template <class ColorGradient>
+struct Scaler3x : public ColorGradient
+{
+    static const int scale = 3;
+
+    template <unsigned int M, unsigned int N> //bring template function into scope for GCC
+    static void alphaGrad(uint32_t& pixBack, uint32_t pixFront) { ColorGradient::template alphaGrad<M, N>(pixBack, pixFront); }
+
+
+    template <class OutputMatrix>
+    static void blendLineShallow(uint32_t col, OutputMatrix& out)
+    {
+        alphaGrad<1, 4>(out.template ref<scale - 1, 0>(), col);
+        alphaGrad<1, 4>(out.template ref<scale - 2, 2>(), col);
+
+        alphaGrad<3, 4>(out.template ref<scale - 1, 1>(), col);
+        out.template ref<scale - 1, 2>() = col;
+    }
+
+    template <class OutputMatrix>
+    static void blendLineSteep(uint32_t col, OutputMatrix& out)
+    {
+        alphaGrad<1, 4>(out.template ref<0, scale - 1>(), col);
+        alphaGrad<1, 4>(out.template ref<2, scale - 2>(), col);
+
+        alphaGrad<3, 4>(out.template ref<1, scale - 1>(), col);
+        out.template ref<2, scale - 1>() = col;
+    }
+
+    template <class OutputMatrix>
+    static void blendLineSteepAndShallow(uint32_t col, OutputMatrix& out)
+    {
+        alphaGrad<1, 4>(out.template ref<2, 0>(), col);
+        alphaGrad<1, 4>(out.template ref<0, 2>(), col);
+        alphaGrad<3, 4>(out.template ref<2, 1>(), col);
+        alphaGrad<3, 4>(out.template ref<1, 2>(), col);
+        out.template ref<2, 2>() = col;
+    }
+
+    template <class OutputMatrix>
+    static void blendLineDiagonal(uint32_t col, OutputMatrix& out)
+    {
+        alphaGrad<1, 8>(out.template ref<1, 2>(), col); //conflict with other rotations for this odd scale
+        alphaGrad<1, 8>(out.template ref<2, 1>(), col);
+        alphaGrad<7, 8>(out.template ref<2, 2>(), col); //
+    }
+
+    template <class OutputMatrix>
+    static void blendCorner(uint32_t col, OutputMatrix& out)
+    {
+        //model a round corner
+        alphaGrad<45, 100>(out.template ref<2, 2>(), col); //exact: 0.4545939598
+        //alphaGrad<7, 256>(out.template ref<2, 1>(), col); //0.02826017254 -> negligible + avoid conflicts with other rotations for this odd scale
+        //alphaGrad<7, 256>(out.template ref<1, 2>(), col); //0.02826017254
+    }
+};
+
+
+template <class ColorGradient>
+struct Scaler4x : public ColorGradient
+{
+    static const int scale = 4;
+
+    template <unsigned int M, unsigned int N> //bring template function into scope for GCC
+    static void alphaGrad(uint32_t& pixBack, uint32_t pixFront) { ColorGradient::template alphaGrad<M, N>(pixBack, pixFront); }
+
+
+    template <class OutputMatrix>
+    static void blendLineShallow(uint32_t col, OutputMatrix& out)
+    {
+        alphaGrad<1, 4>(out.template ref<scale - 1, 0>(), col);
+        alphaGrad<1, 4>(out.template ref<scale - 2, 2>(), col);
+
+        alphaGrad<3, 4>(out.template ref<scale - 1, 1>(), col);
+        alphaGrad<3, 4>(out.template ref<scale - 2, 3>(), col);
+
+        out.template ref<scale - 1, 2>() = col;
+        out.template ref<scale - 1, 3>() = col;
+    }
+
+    template <class OutputMatrix>
+    static void blendLineSteep(uint32_t col, OutputMatrix& out)
+    {
+        alphaGrad<1, 4>(out.template ref<0, scale - 1>(), col);
+        alphaGrad<1, 4>(out.template ref<2, scale - 2>(), col);
+
+        alphaGrad<3, 4>(out.template ref<1, scale - 1>(), col);
+        alphaGrad<3, 4>(out.template ref<3, scale - 2>(), col);
+
+        out.template ref<2, scale - 1>() = col;
+        out.template ref<3, scale - 1>() = col;
+    }
+
+    template <class OutputMatrix>
+    static void blendLineSteepAndShallow(uint32_t col, OutputMatrix& out)
+    {
+        alphaGrad<3, 4>(out.template ref<3, 1>(), col);
+        alphaGrad<3, 4>(out.template ref<1, 3>(), col);
+        alphaGrad<1, 4>(out.template ref<3, 0>(), col);
+        alphaGrad<1, 4>(out.template ref<0, 3>(), col);
+
+        alphaGrad<1, 3>(out.template ref<2, 2>(), col); //[!] fixes 1/4 used in xBR
+
+        out.template ref<3, 3>() = col;
+        out.template ref<3, 2>() = col;
+        out.template ref<2, 3>() = col;
+    }
+
+    template <class OutputMatrix>
+    static void blendLineDiagonal(uint32_t col, OutputMatrix& out)
+    {
+        alphaGrad<1, 2>(out.template ref<scale - 1, scale / 2    >(), col);
+        alphaGrad<1, 2>(out.template ref<scale - 2, scale / 2 + 1>(), col);
+        out.template ref<scale - 1, scale - 1>() = col;
+    }
+
+    template <class OutputMatrix>
+    static void blendCorner(uint32_t col, OutputMatrix& out)
+    {
+        //model a round corner
+        alphaGrad<68, 100>(out.template ref<3, 3>(), col); //exact: 0.6848532563
+        alphaGrad< 9, 100>(out.template ref<3, 2>(), col); //0.08677704501
+        alphaGrad< 9, 100>(out.template ref<2, 3>(), col); //0.08677704501
+    }
+};
+
+
+template <class ColorGradient>
+struct Scaler5x : public ColorGradient
+{
+    static const int scale = 5;
+
+    template <unsigned int M, unsigned int N> //bring template function into scope for GCC
+    static void alphaGrad(uint32_t& pixBack, uint32_t pixFront) { ColorGradient::template alphaGrad<M, N>(pixBack, pixFront); }
+
+
+    template <class OutputMatrix>
+    static void blendLineShallow(uint32_t col, OutputMatrix& out)
+    {
+        alphaGrad<1, 4>(out.template ref<scale - 1, 0>(), col);
+        alphaGrad<1, 4>(out.template ref<scale - 2, 2>(), col);
+        alphaGrad<1, 4>(out.template ref<scale - 3, 4>(), col);
+
+        alphaGrad<3, 4>(out.template ref<scale - 1, 1>(), col);
+        alphaGrad<3, 4>(out.template ref<scale - 2, 3>(), col);
+
+        out.template ref<scale - 1, 2>() = col;
+        out.template ref<scale - 1, 3>() = col;
+        out.template ref<scale - 1, 4>() = col;
+        out.template ref<scale - 2, 4>() = col;
+    }
+
+    template <class OutputMatrix>
+    static void blendLineSteep(uint32_t col, OutputMatrix& out)
+    {
+        alphaGrad<1, 4>(out.template ref<0, scale - 1>(), col);
+        alphaGrad<1, 4>(out.template ref<2, scale - 2>(), col);
+        alphaGrad<1, 4>(out.template ref<4, scale - 3>(), col);
+
+        alphaGrad<3, 4>(out.template ref<1, scale - 1>(), col);
+        alphaGrad<3, 4>(out.template ref<3, scale - 2>(), col);
+
+        out.template ref<2, scale - 1>() = col;
+        out.template ref<3, scale - 1>() = col;
+        out.template ref<4, scale - 1>() = col;
+        out.template ref<4, scale - 2>() = col;
+    }
+
+    template <class OutputMatrix>
+    static void blendLineSteepAndShallow(uint32_t col, OutputMatrix& out)
+    {
+        alphaGrad<1, 4>(out.template ref<0, scale - 1>(), col);
+        alphaGrad<1, 4>(out.template ref<2, scale - 2>(), col);
+        alphaGrad<3, 4>(out.template ref<1, scale - 1>(), col);
+
+        alphaGrad<1, 4>(out.template ref<scale - 1, 0>(), col);
+        alphaGrad<1, 4>(out.template ref<scale - 2, 2>(), col);
+        alphaGrad<3, 4>(out.template ref<scale - 1, 1>(), col);
+
+        alphaGrad<2, 3>(out.template ref<3, 3>(), col);
+
+        out.template ref<2, scale - 1>() = col;
+        out.template ref<3, scale - 1>() = col;
+        out.template ref<4, scale - 1>() = col;
+
+        out.template ref<scale - 1, 2>() = col;
+        out.template ref<scale - 1, 3>() = col;
+    }
+
+    template <class OutputMatrix>
+    static void blendLineDiagonal(uint32_t col, OutputMatrix& out)
+    {
+        alphaGrad<1, 8>(out.template ref<scale - 1, scale / 2    >(), col); //conflict with other rotations for this odd scale
+        alphaGrad<1, 8>(out.template ref<scale - 2, scale / 2 + 1>(), col);
+        alphaGrad<1, 8>(out.template ref<scale - 3, scale / 2 + 2>(), col); //
+
+        alphaGrad<7, 8>(out.template ref<4, 3>(), col);
+        alphaGrad<7, 8>(out.template ref<3, 4>(), col);
+
+        out.template ref<4, 4>() = col;
+    }
+
+    template <class OutputMatrix>
+    static void blendCorner(uint32_t col, OutputMatrix& out)
+    {
+        //model a round corner
+        alphaGrad<86, 100>(out.template ref<4, 4>(), col); //exact: 0.8631434088
+        alphaGrad<23, 100>(out.template ref<4, 3>(), col); //0.2306749731
+        alphaGrad<23, 100>(out.template ref<3, 4>(), col); //0.2306749731
+        //alphaGrad<1, 64>(out.template ref<4, 2>(), col); //0.01676812367 -> negligible + avoid conflicts with other rotations for this odd scale
+        //alphaGrad<1, 64>(out.template ref<2, 4>(), col); //0.01676812367
+    }
+};
+
+
+template <class ColorGradient>
+struct Scaler6x : public ColorGradient
+{
+    static const int scale = 6;
+
+    template <unsigned int M, unsigned int N> //bring template function into scope for GCC
+    static void alphaGrad(uint32_t& pixBack, uint32_t pixFront) { ColorGradient::template alphaGrad<M, N>(pixBack, pixFront); }
+
+
+    template <class OutputMatrix>
+    static void blendLineShallow(uint32_t col, OutputMatrix& out)
+    {
+        alphaGrad<1, 4>(out.template ref<scale - 1, 0>(), col);
+        alphaGrad<1, 4>(out.template ref<scale - 2, 2>(), col);
+        alphaGrad<1, 4>(out.template ref<scale - 3, 4>(), col);
+
+        alphaGrad<3, 4>(out.template ref<scale - 1, 1>(), col);
+        alphaGrad<3, 4>(out.template ref<scale - 2, 3>(), col);
+        alphaGrad<3, 4>(out.template ref<scale - 3, 5>(), col);
+
+        out.template ref<scale - 1, 2>() = col;
+        out.template ref<scale - 1, 3>() = col;
+        out.template ref<scale - 1, 4>() = col;
+        out.template ref<scale - 1, 5>() = col;
+
+        out.template ref<scale - 2, 4>() = col;
+        out.template ref<scale - 2, 5>() = col;
+    }
+
+    template <class OutputMatrix>
+    static void blendLineSteep(uint32_t col, OutputMatrix& out)
+    {
+        alphaGrad<1, 4>(out.template ref<0, scale - 1>(), col);
+        alphaGrad<1, 4>(out.template ref<2, scale - 2>(), col);
+        alphaGrad<1, 4>(out.template ref<4, scale - 3>(), col);
+
+        alphaGrad<3, 4>(out.template ref<1, scale - 1>(), col);
+        alphaGrad<3, 4>(out.template ref<3, scale - 2>(), col);
+        alphaGrad<3, 4>(out.template ref<5, scale - 3>(), col);
+
+        out.template ref<2, scale - 1>() = col;
+        out.template ref<3, scale - 1>() = col;
+        out.template ref<4, scale - 1>() = col;
+        out.template ref<5, scale - 1>() = col;
+
+        out.template ref<4, scale - 2>() = col;
+        out.template ref<5, scale - 2>() = col;
+    }
+
+    template <class OutputMatrix>
+    static void blendLineSteepAndShallow(uint32_t col, OutputMatrix& out)
+    {
+        alphaGrad<1, 4>(out.template ref<0, scale - 1>(), col);
+        alphaGrad<1, 4>(out.template ref<2, scale - 2>(), col);
+        alphaGrad<3, 4>(out.template ref<1, scale - 1>(), col);
+        alphaGrad<3, 4>(out.template ref<3, scale - 2>(), col);
+
+        alphaGrad<1, 4>(out.template ref<scale - 1, 0>(), col);
+        alphaGrad<1, 4>(out.template ref<scale - 2, 2>(), col);
+        alphaGrad<3, 4>(out.template ref<scale - 1, 1>(), col);
+        alphaGrad<3, 4>(out.template ref<scale - 2, 3>(), col);
+
+        out.template ref<2, scale - 1>() = col;
+        out.template ref<3, scale - 1>() = col;
+        out.template ref<4, scale - 1>() = col;
+        out.template ref<5, scale - 1>() = col;
+
+        out.template ref<4, scale - 2>() = col;
+        out.template ref<5, scale - 2>() = col;
+
+        out.template ref<scale - 1, 2>() = col;
+        out.template ref<scale - 1, 3>() = col;
+    }
+
+    template <class OutputMatrix>
+    static void blendLineDiagonal(uint32_t col, OutputMatrix& out)
+    {
+        alphaGrad<1, 2>(out.template ref<scale - 1, scale / 2    >(), col);
+        alphaGrad<1, 2>(out.template ref<scale - 2, scale / 2 + 1>(), col);
+        alphaGrad<1, 2>(out.template ref<scale - 3, scale / 2 + 2>(), col);
+
+        out.template ref<scale - 2, scale - 1>() = col;
+        out.template ref<scale - 1, scale - 1>() = col;
+        out.template ref<scale - 1, scale - 2>() = col;
+    }
+
+    template <class OutputMatrix>
+    static void blendCorner(uint32_t col, OutputMatrix& out)
+    {
+        //model a round corner
+        alphaGrad<97, 100>(out.template ref<5, 5>(), col); //exact: 0.9711013910
+        alphaGrad<42, 100>(out.template ref<4, 5>(), col); //0.4236372243
+        alphaGrad<42, 100>(out.template ref<5, 4>(), col); //0.4236372243
+        alphaGrad< 6, 100>(out.template ref<5, 3>(), col); //0.05652034508
+        alphaGrad< 6, 100>(out.template ref<3, 5>(), col); //0.05652034508
+    }
+};
+
+//------------------------------------------------------------------------------------
+
+struct ColorDistanceRGB
+{
+    static double dist(uint32_t pix1, uint32_t pix2, double luminanceWeight)
+    {
+        return distYCbCrBuffered(pix1, pix2);
+
+        //if (pix1 == pix2) //about 4% perf boost
+        //    return 0;
+        //return distYCbCr(pix1, pix2, luminanceWeight);
+    }
+};
+
+struct ColorDistanceARGB
+{
+    static double dist(uint32_t pix1, uint32_t pix2, double luminanceWeight)
+    {
+        const double a1 = getAlpha(pix1) / 255.0 ;
+        const double a2 = getAlpha(pix2) / 255.0 ;
+        /*
+        Requirements for a color distance handling alpha channel: with a1, a2 in [0, 1]
+
+            1. if a1 = a2, distance should be: a1 * distYCbCr()
+            2. if a1 = 0,  distance should be: a2 * distYCbCr(black, white) = a2 * 255
+            3. if a1 = 1,  ??? maybe: 255 * (1 - a2) + a2 * distYCbCr()
+        */
+
+        //return std::min(a1, a2) * distYCbCrBuffered(pix1, pix2) + 255 * abs(a1 - a2);
+        //=> following code is 15% faster:
+        const double d = distYCbCrBuffered(pix1, pix2);
+        if (a1 < a2)
+            return a1 * d + 255 * (a2 - a1);
+        else
+            return a2 * d + 255 * (a1 - a2);
+
+        //alternative? return std::sqrt(a1 * a2 * square(distYCbCrBuffered(pix1, pix2)) + square(255 * (a1 - a2)));
+    }
+};
+
+
+struct ColorDistanceUnbufferedARGB
+{
+    static double dist(uint32_t pix1, uint32_t pix2, double luminanceWeight)
+    {
+        const double a1 = getAlpha(pix1) / 255.0 ;
+        const double a2 = getAlpha(pix2) / 255.0 ;
+
+        const double d = distYCbCr(pix1, pix2, luminanceWeight);
+        if (a1 < a2)
+            return a1 * d + 255 * (a2 - a1);
+        else
+            return a2 * d + 255 * (a1 - a2);
+    }
+};
+
+
+struct ColorGradientRGB
+{
+    template <unsigned int M, unsigned int N>
+    static void alphaGrad(uint32_t& pixBack, uint32_t pixFront)
+    {
+        pixBack = gradientRGB<M, N>(pixFront, pixBack);
+    }
+};
+
+struct ColorGradientARGB
+{
+    template <unsigned int M, unsigned int N>
+    static void alphaGrad(uint32_t& pixBack, uint32_t pixFront)
+    {
+        pixBack = gradientARGB<M, N>(pixFront, pixBack);
+    }
+};
+}
+
+
+void xbrz::scale(size_t factor, const uint32_t* src, uint32_t* trg, int srcWidth, int srcHeight, ColorFormat colFmt, const xbrz::ScalerCfg& cfg, int yFirst, int yLast)
+{
+    if (factor == 1)
+    {
+        std::copy(src + yFirst * srcWidth, src + yLast * srcWidth, trg);
+        return;
+    }
+
+    static_assert(SCALE_FACTOR_MAX == 6);
+    switch (colFmt)
+    {
+        case ColorFormat::RGB:
+            switch (factor)
+            {
+                case 2:
+                    return scaleImage<Scaler2x<ColorGradientRGB>, ColorDistanceRGB, OobReaderDuplicate>(src, trg, srcWidth, srcHeight, cfg, yFirst, yLast);
+                case 3:
+                    return scaleImage<Scaler3x<ColorGradientRGB>, ColorDistanceRGB, OobReaderDuplicate>(src, trg, srcWidth, srcHeight, cfg, yFirst, yLast);
+                case 4:
+                    return scaleImage<Scaler4x<ColorGradientRGB>, ColorDistanceRGB, OobReaderDuplicate>(src, trg, srcWidth, srcHeight, cfg, yFirst, yLast);
+                case 5:
+                    return scaleImage<Scaler5x<ColorGradientRGB>, ColorDistanceRGB, OobReaderDuplicate>(src, trg, srcWidth, srcHeight, cfg, yFirst, yLast);
+                case 6:
+                    return scaleImage<Scaler6x<ColorGradientRGB>, ColorDistanceRGB, OobReaderDuplicate>(src, trg, srcWidth, srcHeight, cfg, yFirst, yLast);
+            }
+            break;
+
+        case ColorFormat::ARGB:
+            switch (factor)
+            {
+                case 2:
+                    return scaleImage<Scaler2x<ColorGradientARGB>, ColorDistanceARGB, OobReaderTransparent>(src, trg, srcWidth, srcHeight, cfg, yFirst, yLast);
+                case 3:
+                    return scaleImage<Scaler3x<ColorGradientARGB>, ColorDistanceARGB, OobReaderTransparent>(src, trg, srcWidth, srcHeight, cfg, yFirst, yLast);
+                case 4:
+                    return scaleImage<Scaler4x<ColorGradientARGB>, ColorDistanceARGB, OobReaderTransparent>(src, trg, srcWidth, srcHeight, cfg, yFirst, yLast);
+                case 5:
+                    return scaleImage<Scaler5x<ColorGradientARGB>, ColorDistanceARGB, OobReaderTransparent>(src, trg, srcWidth, srcHeight, cfg, yFirst, yLast);
+                case 6:
+                    return scaleImage<Scaler6x<ColorGradientARGB>, ColorDistanceARGB, OobReaderTransparent>(src, trg, srcWidth, srcHeight, cfg, yFirst, yLast);
+            }
+            break;
+
+        case ColorFormat::ARGB_UNBUFFERED:
+            switch (factor)
+            {
+                case 2:
+                    return scaleImage<Scaler2x<ColorGradientARGB>, ColorDistanceUnbufferedARGB, OobReaderTransparent>(src, trg, srcWidth, srcHeight, cfg, yFirst, yLast);
+                case 3:
+                    return scaleImage<Scaler3x<ColorGradientARGB>, ColorDistanceUnbufferedARGB, OobReaderTransparent>(src, trg, srcWidth, srcHeight, cfg, yFirst, yLast);
+                case 4:
+                    return scaleImage<Scaler4x<ColorGradientARGB>, ColorDistanceUnbufferedARGB, OobReaderTransparent>(src, trg, srcWidth, srcHeight, cfg, yFirst, yLast);
+                case 5:
+                    return scaleImage<Scaler5x<ColorGradientARGB>, ColorDistanceUnbufferedARGB, OobReaderTransparent>(src, trg, srcWidth, srcHeight, cfg, yFirst, yLast);
+                case 6:
+                    return scaleImage<Scaler6x<ColorGradientARGB>, ColorDistanceUnbufferedARGB, OobReaderTransparent>(src, trg, srcWidth, srcHeight, cfg, yFirst, yLast);
+            }
+            break;
+    }
+    assert(false);
+}
+
+
+bool xbrz::equalColorTest(uint32_t col1, uint32_t col2, ColorFormat colFmt, double luminanceWeight, double equalColorTolerance)
+{
+    switch (colFmt)
+    {
+        case ColorFormat::RGB:
+            return ColorDistanceRGB::dist(col1, col2, luminanceWeight) < equalColorTolerance;
+        case ColorFormat::ARGB:
+            return ColorDistanceARGB::dist(col1, col2, luminanceWeight) < equalColorTolerance;
+        case ColorFormat::ARGB_UNBUFFERED:
+            return ColorDistanceUnbufferedARGB::dist(col1, col2, luminanceWeight) < equalColorTolerance;
+    }
+    assert(false);
+    return false;
+}
+
+
+void xbrz::bilinearScale(const uint32_t* src, int srcWidth, int srcHeight,
+                         /**/  uint32_t* trg, int trgWidth, int trgHeight)
+{
+    bilinearScale(src, srcWidth, srcHeight, srcWidth * sizeof(uint32_t),
+                  trg, trgWidth, trgHeight, trgWidth * sizeof(uint32_t),
+    0, trgHeight, [](uint32_t pix) { return pix; });
+}
+
+
+void xbrz::nearestNeighborScale(const uint32_t* src, int srcWidth, int srcHeight,
+                                /**/  uint32_t* trg, int trgWidth, int trgHeight)
+{
+    nearestNeighborScale(src, srcWidth, srcHeight, srcWidth * sizeof(uint32_t),
+                         trg, trgWidth, trgHeight, trgWidth * sizeof(uint32_t),
+    0, trgHeight, [](uint32_t pix) { return pix; });
+}
+
+
+#if 0
+//#include <ppl.h>
+void bilinearScaleCpu(const uint32_t* src, int srcWidth, int srcHeight,
+                      /**/  uint32_t* trg, int trgWidth, int trgHeight)
+{
+    const int TASK_GRANULARITY = 16;
+
+    concurrency::task_group tg;
+
+    for (int i = 0; i < trgHeight; i += TASK_GRANULARITY)
+        tg.run([=]
+    {
+        const int iLast = std::min(i + TASK_GRANULARITY, trgHeight);
+        xbrz::bilinearScale(src, srcWidth, srcHeight, srcWidth * sizeof(uint32_t),
+                            trg, trgWidth, trgHeight, trgWidth * sizeof(uint32_t),
+        i, iLast, [](uint32_t pix) { return pix; });
+    });
+    tg.wait();
+}
+
+
+//Perf: AMP vs CPU: merely ~10% shorter runtime (scaling 1280x800 -> 1920x1080)
+//#include <amp.h>
+void bilinearScaleAmp(const uint32_t* src, int srcWidth, int srcHeight, //throw concurrency::runtime_exception
+                      /**/  uint32_t* trg, int trgWidth, int trgHeight)
+{
+    //C++ AMP reference:       https://msdn.microsoft.com/en-us/library/hh289390.aspx
+    //introduction to C++ AMP: https://msdn.microsoft.com/en-us/magazine/hh882446.aspx
+    using namespace concurrency;
+    //TODO: pitch
+
+    if (srcHeight <= 0 || srcWidth <= 0) return;
+
+    const float scaleX = static_cast<float>(trgWidth ) / srcWidth;
+    const float scaleY = static_cast<float>(trgHeight) / srcHeight;
+
+    array_view<const uint32_t, 2> srcView(srcHeight, srcWidth, src);
+    array_view<      uint32_t, 2> trgView(trgHeight, trgWidth, trg);
+    trgView.discard_data();
+
+    parallel_for_each(trgView.extent, [=](index<2> idx) restrict(amp) //throw ?
+    {
+        const int y = idx[0];
+        const int x = idx[1];
+        //Perf notes:
+        //    -> float-based calculation is (almost) 2x as fas as double!
+        //    -> no noticeable improvement via tiling: https://msdn.microsoft.com/en-us/magazine/hh882447.aspx
+        //    -> no noticeable improvement with restrict(amp,cpu)
+        //    -> iterating over y-axis only is significantly slower!
+        //    -> pre-calculating x,y-dependent variables in a buffer + array_view<> is ~ 20 % slower!
+        const int y1 = srcHeight * y / trgHeight;
+        int y2 = y1 + 1;
+        if (y2 == srcHeight) --y2;
+
+        const float yy1 = y / scaleY - y1;
+        const float y2y = 1 - yy1;
+        //-------------------------------------
+        const int x1 = srcWidth * x / trgWidth;
+        int x2 = x1 + 1;
+        if (x2 == srcWidth) --x2;
+
+        const float xx1 = x / scaleX - x1;
+        const float x2x = 1 - xx1;
+        //-------------------------------------
+        const float x2xy2y = x2x * y2y;
+        const float xx1y2y = xx1 * y2y;
+        const float x2xyy1 = x2x * yy1;
+        const float xx1yy1 = xx1 * yy1;
+
+        auto interpolate = [=](int offset)
+        {
+            /*
+                https://en.wikipedia.org/wiki/Bilinear_interpolation
+                (c11(x2 - x) + c21(x - x1)) * (y2 - y ) +
+                (c12(x2 - x) + c22(x - x1)) * (y  - y1)
+            */
+            const auto c11 = (srcView(y1, x1) >> (8 * offset)) & 0xff;
+            const auto c21 = (srcView(y1, x2) >> (8 * offset)) & 0xff;
+            const auto c12 = (srcView(y2, x1) >> (8 * offset)) & 0xff;
+            const auto c22 = (srcView(y2, x2) >> (8 * offset)) & 0xff;
+
+            return c11 * x2xy2y + c21 * xx1y2y +
+                   c12 * x2xyy1 + c22 * xx1yy1;
+        };
+
+        const float bi = interpolate(0);
+        const float gi = interpolate(1);
+        const float ri = interpolate(2);
+        const float ai = interpolate(3);
+
+        const auto b = static_cast<uint32_t>(bi + 0.5f);
+        const auto g = static_cast<uint32_t>(gi + 0.5f);
+        const auto r = static_cast<uint32_t>(ri + 0.5f);
+        const auto a = static_cast<uint32_t>(ai + 0.5f);
+
+        trgView(y, x) = (a << 24) | (r << 16) | (g << 8) | b;
+    });
+    trgView.synchronize(); //throw ?
+}
+#endif

+ 79 - 0
client/xBRZ/xbrz.h

@@ -0,0 +1,79 @@
+// ****************************************************************************
+// * This file is part of the xBRZ project. It is distributed under           *
+// * GNU General Public License: https://www.gnu.org/licenses/gpl-3.0         *
+// * Copyright (C) Zenju (zenju AT gmx DOT de) - All Rights Reserved          *
+// *                                                                          *
+// * Additionally and as a special exception, the author gives permission     *
+// * to link the code of this program with the following libraries            *
+// * (or with modified versions that use the same licenses), and distribute   *
+// * linked combinations including the two: MAME, FreeFileSync, Snes9x, ePSXe *
+// * You must obey the GNU General Public License in all respects for all of  *
+// * the code used other than MAME, FreeFileSync, Snes9x, ePSXe.              *
+// * If you modify this file, you may extend this exception to your version   *
+// * of the file, but you are not obligated to do so. If you do not wish to   *
+// * do so, delete this exception statement from your version.                *
+// ****************************************************************************
+
+#ifndef XBRZ_HEADER_3847894708239054
+#define XBRZ_HEADER_3847894708239054
+
+#include <cstddef> //size_t
+#include <cstdint> //uint32_t
+#include <limits>
+#include "xbrz_config.h"
+
+
+namespace xbrz
+{
+/*
+-------------------------------------------------------------------------
+| xBRZ: "Scale by rules" - high quality image upscaling filter by Zenju |
+-------------------------------------------------------------------------
+using a modified approach of xBR:
+http://board.byuu.org/viewtopic.php?f=10&t=2248
+- new rule set preserving small image features
+- highly optimized for performance
+- support alpha channel
+- support multithreading
+- support 64-bit architectures
+- support processing image slices
+- support scaling up to 6xBRZ
+*/
+
+enum class ColorFormat //from high bits -> low bits, 8 bit per channel
+{
+    RGB,  //8 bit for each red, green, blue, upper 8 bits unused
+    ARGB, //including alpha channel, BGRA byte order on little-endian machines
+    ARGB_UNBUFFERED, //like ARGB, but without the one-time buffer creation overhead (ca. 100 - 300 ms) at the expense of a slightly slower scaling time
+};
+
+const int SCALE_FACTOR_MAX = 6;
+
+/*
+-> map source (srcWidth * srcHeight) to target (scale * width x scale * height) image, optionally processing a half-open slice of rows [yFirst, yLast) only
+-> if your emulator changes only a few image slices during each cycle (e.g. DOSBox) then there's no need to run xBRZ on the complete image:
+   Just make sure you enlarge the source image slice by 2 rows on top and 2 on bottom (this is the additional range the xBRZ algorithm is using during analysis)
+   CAVEAT: If there are multiple changed slices, make sure they do not overlap after adding these additional rows in order to avoid a memory race condition
+   in the target image data if you are using multiple threads for processing each enlarged slice!
+
+THREAD-SAFETY: - parts of the same image may be scaled by multiple threads as long as the [yFirst, yLast) ranges do not overlap!
+               - there is a minor inefficiency for the first row of a slice, so avoid processing single rows only; suggestion: process at least 8-16 rows
+*/
+void scale(size_t factor, //valid range: 2 - SCALE_FACTOR_MAX
+           const uint32_t* src, uint32_t* trg, int srcWidth, int srcHeight,
+           ColorFormat colFmt,
+           const ScalerCfg& cfg = ScalerCfg(),
+           int yFirst = 0, int yLast = std::numeric_limits<int>::max()); //slice of source image
+
+void bilinearScale(const uint32_t* src, int srcWidth, int srcHeight,
+                   /**/  uint32_t* trg, int trgWidth, int trgHeight);
+
+void nearestNeighborScale(const uint32_t* src, int srcWidth, int srcHeight,
+                          /**/  uint32_t* trg, int trgWidth, int trgHeight);
+
+
+//parameter tuning
+bool equalColorTest(uint32_t col1, uint32_t col2, ColorFormat colFmt, double luminanceWeight, double equalColorTolerance);
+}
+
+#endif

+ 35 - 0
client/xBRZ/xbrz_config.h

@@ -0,0 +1,35 @@
+// ****************************************************************************
+// * This file is part of the xBRZ project. It is distributed under           *
+// * GNU General Public License: https://www.gnu.org/licenses/gpl-3.0         *
+// * Copyright (C) Zenju (zenju AT gmx DOT de) - All Rights Reserved          *
+// *                                                                          *
+// * Additionally and as a special exception, the author gives permission     *
+// * to link the code of this program with the following libraries            *
+// * (or with modified versions that use the same licenses), and distribute   *
+// * linked combinations including the two: MAME, FreeFileSync, Snes9x, ePSXe *
+// * You must obey the GNU General Public License in all respects for all of  *
+// * the code used other than MAME, FreeFileSync, Snes9x, ePSXe.              *
+// * If you modify this file, you may extend this exception to your version   *
+// * of the file, but you are not obligated to do so. If you do not wish to   *
+// * do so, delete this exception statement from your version.                *
+// ****************************************************************************
+
+#ifndef XBRZ_CONFIG_HEADER_284578425345
+#define XBRZ_CONFIG_HEADER_284578425345
+
+//do NOT include any headers here! used by xBRZ_dll!!!
+
+namespace xbrz
+{
+struct ScalerCfg
+{
+    double luminanceWeight            = 1;
+    double equalColorTolerance        = 30;
+    double centerDirectionBias        = 4;
+    double dominantDirectionThreshold = 3.6;
+    double steepDirectionThreshold    = 2.2;
+    double newTestAttribute           = 0; //unused; test new parameters
+};
+}
+
+#endif

+ 266 - 0
client/xBRZ/xbrz_tools.h

@@ -0,0 +1,266 @@
+// ****************************************************************************
+// * This file is part of the xBRZ project. It is distributed under           *
+// * GNU General Public License: https://www.gnu.org/licenses/gpl-3.0         *
+// * Copyright (C) Zenju (zenju AT gmx DOT de) - All Rights Reserved          *
+// *                                                                          *
+// * Additionally and as a special exception, the author gives permission     *
+// * to link the code of this program with the following libraries            *
+// * (or with modified versions that use the same licenses), and distribute   *
+// * linked combinations including the two: MAME, FreeFileSync, Snes9x, ePSXe *
+// * You must obey the GNU General Public License in all respects for all of  *
+// * the code used other than MAME, FreeFileSync, Snes9x, ePSXe.              *
+// * If you modify this file, you may extend this exception to your version   *
+// * of the file, but you are not obligated to do so. If you do not wish to   *
+// * do so, delete this exception statement from your version.                *
+// ****************************************************************************
+
+#ifndef XBRZ_TOOLS_H_825480175091875
+#define XBRZ_TOOLS_H_825480175091875
+
+#include <cassert>
+#include <algorithm>
+#include <type_traits>
+
+
+namespace xbrz
+{
+template <uint32_t N> inline
+unsigned char getByte(uint32_t val) { return static_cast<unsigned char>((val >> (8 * N)) & 0xff); }
+
+inline unsigned char getAlpha(uint32_t pix) { return getByte<3>(pix); }
+inline unsigned char getRed  (uint32_t pix) { return getByte<2>(pix); }
+inline unsigned char getGreen(uint32_t pix) { return getByte<1>(pix); }
+inline unsigned char getBlue (uint32_t pix) { return getByte<0>(pix); }
+
+inline uint32_t makePixel(unsigned char a, unsigned char r, unsigned char g, unsigned char b) { return (a << 24) | (r << 16) | (g << 8) | b; }
+inline uint32_t makePixel(                 unsigned char r, unsigned char g, unsigned char b) { return             (r << 16) | (g << 8) | b; }
+
+inline uint32_t rgb555to888(uint16_t pix) { return ((pix & 0x7C00) << 9) | ((pix & 0x03E0) << 6) | ((pix & 0x001F) << 3); }
+inline uint32_t rgb565to888(uint16_t pix) { return ((pix & 0xF800) << 8) | ((pix & 0x07E0) << 5) | ((pix & 0x001F) << 3); }
+
+inline uint16_t rgb888to555(uint32_t pix) { return static_cast<uint16_t>(((pix & 0xF80000) >> 9) | ((pix & 0x00F800) >> 6) | ((pix & 0x0000F8) >> 3)); }
+inline uint16_t rgb888to565(uint32_t pix) { return static_cast<uint16_t>(((pix & 0xF80000) >> 8) | ((pix & 0x00FC00) >> 5) | ((pix & 0x0000F8) >> 3)); }
+
+
+template <class Pix> inline
+Pix* byteAdvance(Pix* ptr, int bytes)
+{
+    using PixNonConst = typename std::remove_cv<Pix>::type;
+    using PixByte     = typename std::conditional<std::is_same<Pix, PixNonConst>::value, char, const char>::type;
+
+    static_assert(std::is_integral<PixNonConst>::value, "Pix* is expected to be cast-able to char*");
+
+    return reinterpret_cast<Pix*>(reinterpret_cast<PixByte*>(ptr) + bytes);
+}
+
+
+//fill block  with the given color
+template <class Pix> inline
+void fillBlock(Pix* trg, int pitch /*[bytes]*/, Pix col, int blockWidth, int blockHeight)
+{
+    //for (int y = 0; y < blockHeight; ++y, trg = byteAdvance(trg, pitch))
+    //    std::fill(trg, trg + blockWidth, col);
+
+    for (int y = 0; y < blockHeight; ++y, trg = byteAdvance(trg, pitch))
+        for (int x = 0; x < blockWidth; ++x)
+            trg[x] = col;
+}
+
+
+//nearest-neighbor (going over target image - slow for upscaling, since source is read multiple times missing out on cache! Fast for similar image sizes!)
+template <class PixSrc, class PixTrg, class PixConverter>
+void nearestNeighborScale(const PixSrc* src, int srcWidth, int srcHeight, int srcPitch /*[bytes]*/,
+                          /**/  PixTrg* trg, int trgWidth, int trgHeight, int trgPitch /*[bytes]*/,
+                          int yFirst, int yLast, PixConverter pixCvrt /*convert PixSrc to PixTrg*/)
+{
+    static_assert(std::is_integral<PixSrc>::value, "PixSrc* is expected to be cast-able to char*");
+    static_assert(std::is_integral<PixTrg>::value, "PixTrg* is expected to be cast-able to char*");
+
+    static_assert(std::is_same<decltype(pixCvrt(PixSrc())), PixTrg>::value, "PixConverter returning wrong pixel format");
+
+    if (srcPitch < srcWidth * static_cast<int>(sizeof(PixSrc))  ||
+        trgPitch < trgWidth * static_cast<int>(sizeof(PixTrg)))
+    {
+        assert(false);
+        return;
+    }
+
+    yFirst = std::max(yFirst, 0);
+    yLast  = std::min(yLast, trgHeight);
+    if (yFirst >= yLast || srcHeight <= 0 || srcWidth <= 0) return;
+
+    for (int y = yFirst; y < yLast; ++y)
+    {
+        const int ySrc = srcHeight * y / trgHeight;
+        const PixSrc* const srcLine = byteAdvance(src, ySrc * srcPitch);
+        PixTrg*       const trgLine = byteAdvance(trg, y    * trgPitch);
+
+        for (int x = 0; x < trgWidth; ++x)
+        {
+            const int xSrc = srcWidth * x / trgWidth;
+            trgLine[x] = pixCvrt(srcLine[xSrc]);
+        }
+    }
+}
+
+
+//nearest-neighbor (going over source image - fast for upscaling, since source is read only once
+template <class PixSrc, class PixTrg, class PixConverter>
+void nearestNeighborScaleOverSource(const PixSrc* src, int srcWidth, int srcHeight, int srcPitch /*[bytes]*/,
+                                    /**/  PixTrg* trg, int trgWidth, int trgHeight, int trgPitch /*[bytes]*/,
+                                    int yFirst, int yLast, PixConverter pixCvrt /*convert PixSrc to PixTrg*/)
+{
+    static_assert(std::is_integral<PixSrc>::value, "PixSrc* is expected to be cast-able to char*");
+    static_assert(std::is_integral<PixTrg>::value, "PixTrg* is expected to be cast-able to char*");
+
+    static_assert(std::is_same<decltype(pixCvrt(PixSrc())), PixTrg>::value, "PixConverter returning wrong pixel format");
+
+    if (srcPitch < srcWidth * static_cast<int>(sizeof(PixSrc))  ||
+        trgPitch < trgWidth * static_cast<int>(sizeof(PixTrg)))
+    {
+        assert(false);
+        return;
+    }
+
+    yFirst = std::max(yFirst, 0);
+    yLast  = std::min(yLast, srcHeight);
+    if (yFirst >= yLast || trgWidth <= 0 || trgHeight <= 0) return;
+
+    for (int y = yFirst; y < yLast; ++y)
+    {
+        //mathematically: ySrc = floor(srcHeight * yTrg / trgHeight)
+        // => search for integers in: [ySrc, ySrc + 1) * trgHeight / srcHeight
+
+        //keep within for loop to support MT input slices!
+        const int yTrgFirst = ( y      * trgHeight + srcHeight - 1) / srcHeight; //=ceil(y * trgHeight / srcHeight)
+        const int yTrgLast  = ((y + 1) * trgHeight + srcHeight - 1) / srcHeight; //=ceil(((y + 1) * trgHeight) / srcHeight)
+        const int blockHeight = yTrgLast - yTrgFirst;
+
+        if (blockHeight > 0)
+        {
+            const PixSrc* srcLine = byteAdvance(src, y         * srcPitch);
+            /**/  PixTrg* trgLine = byteAdvance(trg, yTrgFirst * trgPitch);
+            int xTrgFirst = 0;
+
+            for (int x = 0; x < srcWidth; ++x)
+            {
+                const int xTrgLast = ((x + 1) * trgWidth + srcWidth - 1) / srcWidth;
+                const int blockWidth = xTrgLast - xTrgFirst;
+                if (blockWidth > 0)
+                {
+                    xTrgFirst = xTrgLast;
+
+                    const auto trgPix = pixCvrt(srcLine[x]);
+                    fillBlock(trgLine, trgPitch, trgPix, blockWidth, blockHeight);
+                    trgLine += blockWidth;
+                }
+            }
+        }
+    }
+}
+
+
+template <class PixTrg, class PixConverter>
+void bilinearScale(const uint32_t* src, int srcWidth, int srcHeight, int srcPitch,
+                   /**/    PixTrg* trg, int trgWidth, int trgHeight, int trgPitch,
+                   int yFirst, int yLast, PixConverter pixCvrt /*convert uint32_t to PixTrg*/)
+{
+    static_assert(std::is_integral<PixTrg>::value,                            "PixTrg* is expected to be cast-able to char*");
+    static_assert(std::is_same<decltype(pixCvrt(uint32_t())), PixTrg>::value, "PixConverter returning wrong pixel format");
+
+    if (srcPitch < srcWidth * static_cast<int>(sizeof(uint32_t)) ||
+        trgPitch < trgWidth * static_cast<int>(sizeof(PixTrg)))
+    {
+        assert(false);
+        return;
+    }
+
+    yFirst = std::max(yFirst, 0);
+    yLast  = std::min(yLast, trgHeight);
+    if (yFirst >= yLast || srcHeight <= 0 || srcWidth <= 0) return;
+
+    const double scaleX = static_cast<double>(trgWidth ) / srcWidth;
+    const double scaleY = static_cast<double>(trgHeight) / srcHeight;
+
+    //perf notes:
+    //    -> double-based calculation is (slightly) faster than float
+    //    -> pre-calculation gives significant boost; std::vector<> memory allocation is negligible!
+    struct CoeffsX
+    {
+        int     x1 = 0;
+        int     x2 = 0;
+        double xx1 = 0;
+        double x2x = 0;
+    };
+    std::vector<CoeffsX> buf(trgWidth);
+    for (int x = 0; x < trgWidth; ++x)
+    {
+        const int x1 = srcWidth * x / trgWidth;
+        int x2 = x1 + 1;
+        if (x2 == srcWidth) --x2;
+
+        const double xx1 = x / scaleX - x1;
+        const double x2x = 1 - xx1;
+
+        buf[x] = { x1, x2, xx1, x2x };
+    }
+
+    for (int y = yFirst; y < yLast; ++y)
+    {
+        const int y1 = srcHeight * y / trgHeight;
+        int y2 = y1 + 1;
+        if (y2 == srcHeight) --y2;
+
+        const double yy1 = y / scaleY - y1;
+        const double y2y = 1 - yy1;
+
+        const uint32_t* const srcLine     = byteAdvance(src, y1 * srcPitch);
+        const uint32_t* const srcLineNext = byteAdvance(src, y2 * srcPitch);
+        PixTrg*         const trgLine     = byteAdvance(trg, y  * trgPitch);
+
+        for (int x = 0; x < trgWidth; ++x)
+        {
+            //perf: do NOT "simplify" the variable layout without measurement!
+            const int     x1 = buf[x].x1;
+            const int     x2 = buf[x].x2;
+            const double xx1 = buf[x].xx1;
+            const double x2x = buf[x].x2x;
+
+            const double x2xy2y = x2x * y2y;
+            const double xx1y2y = xx1 * y2y;
+            const double x2xyy1 = x2x * yy1;
+            const double xx1yy1 = xx1 * yy1;
+
+            auto interpolate = [=](int offset)
+            {
+                /* https://en.wikipedia.org/wiki/Bilinear_interpolation
+                     (c11(x2 - x) + c21(x - x1)) * (y2 - y ) +
+                     (c12(x2 - x) + c22(x - x1)) * (y  - y1)                          */
+                const auto c11 = (srcLine    [x1] >> (8 * offset)) & 0xff;
+                const auto c21 = (srcLine    [x2] >> (8 * offset)) & 0xff;
+                const auto c12 = (srcLineNext[x1] >> (8 * offset)) & 0xff;
+                const auto c22 = (srcLineNext[x2] >> (8 * offset)) & 0xff;
+
+                return c11 * x2xy2y + c21 * xx1y2y +
+                       c12 * x2xyy1 + c22 * xx1yy1;
+            };
+
+            const double bi = interpolate(0);
+            const double gi = interpolate(1);
+            const double ri = interpolate(2);
+            const double ai = interpolate(3);
+
+            const auto b = static_cast<uint32_t>(bi + 0.5);
+            const auto g = static_cast<uint32_t>(gi + 0.5);
+            const auto r = static_cast<uint32_t>(ri + 0.5);
+            const auto a = static_cast<uint32_t>(ai + 0.5);
+
+            const uint32_t trgPix = (a << 24) | (r << 16) | (g << 8) | b;
+
+            trgLine[x] = pixCvrt(trgPix);
+        }
+    }
+}
+}
+
+#endif //XBRZ_TOOLS_H_825480175091875