PicView/src/PicView/ImageHandling/Base64.cs

using ImageMagick;
using PicView.UILogic;
using System.IO;
using System.Windows;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;
using System.Windows.Threading;

namespace PicView.ImageHandling
{
    internal static class Base64
    {
        /// <summary>
        /// Converts a Base64 string to a BitmapSource asynchronously.
        /// </summary>
        /// <param name="base64String">The Base64 string representing the image.</param>
        /// <returns>The BitmapSource created from the Base64 string, or null if conversion fails.</returns>
        internal static async Task<BitmapSource?> Base64StringToBitmapAsync(string base64String)
        {
            return await GetBitmapSourceFromBase64Async(base64String).ConfigureAwait(false);
        }

        /// <summary>
        /// Converts the contents of a file to a BitmapSource asynchronously.
        /// </summary>
        /// <param name="fileInfo">The file to read the Base64 string from.</param>
        /// <returns>The BitmapSource created from the Base64 string in the file, or null if conversion fails.</returns>
        internal static async Task<BitmapSource?> Base64StringToBitmapAsync(FileInfo fileInfo)
        {
            var base64String = await File.ReadAllTextAsync(fileInfo.FullName).ConfigureAwait(false);
            return await GetBitmapSourceFromBase64Async(base64String).ConfigureAwait(false);
        }

        /// <summary>
        /// Converts a Base64 string to a BitmapSource asynchronously.
        /// </summary>
        /// <param name="base64String">The Base64 string representing the image.</param>
        /// <returns>The BitmapSource created from the Base64 string, or null if conversion fails.</returns>
        private static async Task<BitmapSource?> GetBitmapSourceFromBase64Async(string base64String)
        {
            try
            {
                var base64Data = Convert.FromBase64String(base64String);
                using var magickImage = new MagickImage
                {
                    Quality = 100,
                    ColorSpace = ColorSpace.Transparent
                };

                var readSettings = new MagickReadSettings
                {
                    Density = new Density(300, 300),
                    BackgroundColor = MagickColors.Transparent
                };

                await magickImage.ReadAsync(new MemoryStream(base64Data), readSettings).ConfigureAwait(false);
                var bitmapSource = magickImage.ToBitmapSource();
                bitmapSource.Freeze();
                return bitmapSource;
            }
            catch (MagickException)
            {
                return null;
            }
        }

        /// <summary>
        /// Determines whether a string is a valid Base64 string.
        /// </summary>
        /// <param name="base64">The string to check.</param>
        /// <returns>True if the string is a valid Base64 string; otherwise, false.</returns>
        internal static bool IsBase64String(string base64)
        {
            if (string.IsNullOrEmpty(base64))
            {
                return false;
            }

            var buffer = new Span<byte>(new byte[base64.Length]);
            return Convert.TryFromBase64String(base64, buffer, out _);
        }

        /// <summary>
        /// Converts the current rendered bitmap frame to a Base64 string.
        /// </summary>
        /// <returns>A Task representing the asynchronous operation.</returns>
        private static async Task<string> ConvertToBase64(string? path = null)
        {
            BitmapFrame frame;
            if (path is null)
            {
                frame = await ConfigureWindows.GetMainWindow.Dispatcher.InvokeAsync(Image2BitmapSource
                    .GetRenderedBitmapFrame);
            }
            else
            {
                var bitmapSource = await Image2BitmapSource.ReturnBitmapSourceAsync(new FileInfo(path)).ConfigureAwait(false);
                var sourceSize = new Size(bitmapSource.PixelWidth, bitmapSource.PixelHeight);
                var rectangle = new Rectangle
                {
                    Fill = new ImageBrush(bitmapSource),
                };
                rectangle.Measure(sourceSize);
                rectangle.Arrange(new Rect(sourceSize));

                var renderedBitmap = new RenderTargetBitmap(bitmapSource.PixelWidth, bitmapSource.PixelHeight,
                    bitmapSource.DpiX, bitmapSource.DpiY, PixelFormats.Default);
                renderedBitmap.Render(rectangle);

                frame = BitmapFrame.Create(renderedBitmap);
                frame.Freeze();
            }

            byte[]? bytes;
            var b64 = "";
            await Task.Run(() =>
            {
                try
                {
                    using var ms = new MemoryStream();
                    var pngBitmapEncoder = new PngBitmapEncoder();
                    pngBitmapEncoder.Frames.Add(frame);
                    pngBitmapEncoder.Save(ms);
                    bytes = ms.ToArray();
                    b64 = Convert.ToBase64String(bytes);
                }
                catch (Exception e)
                {
                    Tooltip.ShowTooltipMessage(e.Message, true, TimeSpan.FromSeconds(5));
                }
            }).ConfigureAwait(false);

            return b64;
        }

        /// <summary>
        /// Converts the current rendered bitmap frame to a Base64 string and sets it to the clipboard.
        /// </summary>
        /// <returns>A Task representing the asynchronous operation.</returns>
        internal static async Task SendToClipboard(string? path = null)
        {
            var base64String = await ConvertToBase64(path).ConfigureAwait(false);
            if (string.IsNullOrWhiteSpace(base64String))
            {
                Tooltip.ShowTooltipMessage(Application.Current.Resources["UnexpectedError"]);
                return;
            }

            await UC.GetPicGallery.Dispatcher.InvokeAsync(() => { Clipboard.SetText(base64String); },
                DispatcherPriority.Background);

            Tooltip.ShowTooltipMessage(Application.Current.Resources["ConvertedToBase64"]);
        }
    }
}