PicView/src/PicView.Core/ImageDecoding/ImageDecoder.cs

using System.Diagnostics;
using ImageMagick;
using ImageMagick.Formats;
using SkiaSharp;

namespace PicView.Core.ImageDecoding
{
    /// <summary>
    /// Provides methods for decoding various image formats.
    /// </summary>
    public static class ImageDecoder
    {
        /// <summary>
        /// Asynchronously reads and returns a MagickImage from the specified FileInfo.
        /// </summary>
        /// <param name="fileInfo">The FileInfo representing the image file.</param>
        /// <returns>A Task containing the MagickImage if successful, otherwise null.</returns>
        public static async Task<MagickImage?> GetMagickImageAsync(FileInfo fileInfo)
        {
            try
            {
                var magickImage = new MagickImage();
                MagickFormat format;
                var extension = fileInfo.Extension.ToLower();
                switch (extension)
                {
                    case ".heic":
                    case ".heif":
                        magickImage.Settings.SetDefines(new HeicReadDefines
                        {
                            PreserveOrientation = true,
                            DepthImage = true,
                        });
                        format = extension is ".heic" ? MagickFormat.Heic : MagickFormat.Heif;
                        break;

                    case ".jp2":
                        magickImage.Settings.SetDefines(new Jp2ReadDefines
                        {
                            QualityLayers = 100,
                        });
                        format = MagickFormat.Jp2;
                        break;

                    case ".tif":
                    case ".tiff":
                        magickImage.Settings.SetDefines(new TiffReadDefines
                        {
                            IgnoreTags = new[]
                            {
                                "34022", // ColorTable
                                "34025", // ImageColorValue
                                "34026", // BackgroundColorValue
                                "32928",
                            },
                        });
                        format = MagickFormat.Tif;
                        break;

                    case ".psd":
                        format = MagickFormat.Psd;
                        break;

                    default:
                        format = MagickFormat.Unknown;
                        break;
                }

                if (fileInfo.Length >= 2147483648)
                {
                    await using var fileStream = new FileStream(fileInfo.FullName, FileMode.Open, FileAccess.Read,
                        FileShare.ReadWrite, bufferSize: 4096, useAsync: fileInfo.Length > 1e+8);

                    // Fixes "The file is too long. This operation is currently limited to supporting files less than 2 gigabytes in size."
                    // ReSharper disable once MethodHasAsyncOverload
                    magickImage.Read(fileStream, format);
                }
                else
                {
                    await magickImage.ReadAsync(fileInfo, format).ConfigureAwait(false);
                }

                magickImage?.AutoOrient();
                return magickImage;
            }
            catch (Exception e)
            {
#if DEBUG
                Trace.WriteLine($"{nameof(GetMagickImageAsync)} {fileInfo.Name} exception, \n {e.Message}");
#endif
                return null;
            }
        }

        /// <summary>
        /// Asynchronously reads and returns a MagickImage from the specified FileInfo for SVG format.
        /// </summary>
        /// <param name="fileInfo">The FileInfo representing the SVG file.</param>
        /// <param name="magickFormat">The MagickFormat for the SVG image (SVG or SVGZ).</param>
        /// <returns>A Task containing the MagickImage for SVG if successful, otherwise null.</returns>
        public static async Task<MagickImage?> GetMagickSvgAsync(FileInfo fileInfo, MagickFormat magickFormat)
        {
            try
            {
                var magickImage = new MagickImage
                {
                    Quality = 100,
                    ColorSpace = ColorSpace.Transparent,
                    BackgroundColor = MagickColors.Transparent,
                    Format = magickFormat,
                };

                // Streams with a length larger than 2GB are not supported, read from file instead
                if (fileInfo.Length >= 2147483648)
                {
                    await Task.Run(() =>
                    {
                        magickImage = new MagickImage();
                        magickImage.Read(fileInfo);
                    }).ConfigureAwait(false);
                }
                else
                {
                    await using var fileStream = new FileStream(fileInfo.FullName, FileMode.Open, FileAccess.Read,
                        FileShare.ReadWrite, bufferSize: 4096, useAsync: fileInfo.Length > 1e+8);
                    var data = new byte[fileStream.Length];
                    // ReSharper disable once MustUseReturnValue
                    await fileStream.ReadAsync(data.AsMemory(0, (int)fileStream.Length)).ConfigureAwait(false);
                    magickImage.Read(data);
                }

                magickImage.Settings.BackgroundColor = MagickColors.Transparent;
                magickImage.Settings.FillColor = MagickColors.Transparent;
                magickImage.Settings.SetDefine("svg:xml-parse-huge", "true");

                return magickImage;
            }
            catch (Exception e)
            {
#if DEBUG
                Trace.WriteLine($"{nameof(GetMagickSvgAsync)} {fileInfo.Name} exception, \n {e.Message}");
#endif
                return null;
            }
        }

        /// <summary>
        /// Asynchronously reads and returns an SKBitmap from the specified FileInfo.
        /// </summary>
        /// <param name="fileInfo">The FileInfo representing the image file.</param>
        /// <returns>A Task containing the SKBitmap if successful, otherwise null.</returns>
        // ReSharper disable once InconsistentNaming
        public static async Task<SKBitmap?> GetSKBitmapAsync(this FileInfo fileInfo)
        {
            try
            {
                await using var fileStream = new FileStream(fileInfo.FullName, FileMode.Open, FileAccess.Read,
                    FileShare.ReadWrite, bufferSize: 4096, useAsync: fileInfo.Length > 1e+8);
                return SKBitmap.Decode(fileStream);
            }
            catch (Exception e)
            {
#if DEBUG
                Trace.WriteLine($"{nameof(GetSKBitmapAsync)} {fileInfo.Name} exception:\n{e.Message}");
#endif
                return null;
            }
        }
    }
}