Remotely/Desktop.Shared/Services/ImageHelper.cs

using Immense.RemoteControl.Desktop.Shared.Extensions;
using Microsoft.Extensions.Logging;
using Microsoft.IO;
using Remotely.Shared.Primitives;
using SkiaSharp;

namespace Immense.RemoteControl.Desktop.Shared.Services;

public interface IImageHelper
{
    SKBitmap CropBitmap(SKBitmap bitmap, SKRect cropArea);
    byte[] EncodeBitmap(SKBitmap bitmap, SKEncodedImageFormat format, int quality);
    SKRect GetDiffArea(SKBitmap currentFrame, SKBitmap? previousFrame, bool forceFullscreen = false);
    Result<SKBitmap> GetImageDiff(SKBitmap currentFrame, SKBitmap? previousFrame, bool forceFullscreen = false);
}

public class ImageHelper : IImageHelper
{
    private static readonly RecyclableMemoryStreamManager _recycleManager = new();
    private readonly ILogger<ImageHelper> _logger;

    public ImageHelper(ILogger<ImageHelper> logger)
    {
        _logger = logger;
    }

    public byte[] EncodeBitmap(SKBitmap bitmap, SKEncodedImageFormat format, int quality)
    {
        using var ms = _recycleManager.GetStream();
        bitmap.Encode(ms, format, quality);
        return ms.ToArray();
    }

    public SKBitmap CropBitmap(SKBitmap bitmap, SKRect cropArea)
    {
        var cropped = new SKBitmap((int)cropArea.Width, (int)cropArea.Height);
        using var canvas = new SKCanvas(cropped);
        canvas.DrawBitmap(
            bitmap,
            cropArea,
            new SKRect(0, 0, cropArea.Width, cropArea.Height));
        return cropped;
    }

    public Result<SKBitmap> GetImageDiff(SKBitmap currentFrame, SKBitmap? previousFrame, bool forceFullscreen = false)
    {
        try
        {
            if (currentFrame is null)
            {
                return Result.Fail<SKBitmap>("Current frame cannot be null.");
            }

            if (previousFrame is null || forceFullscreen)
            {
                return Result.Ok(currentFrame.Copy());
            }


            if (currentFrame.Height != previousFrame.Height ||
                currentFrame.Width != previousFrame.Width ||
                currentFrame.BytesPerPixel != previousFrame.BytesPerPixel)
            {
                return Result.Fail<SKBitmap>("Frames are not of equal size.");
            }

            var width = currentFrame.Width;
            var height = currentFrame.Height;
            var anyChanges = false;
            var diffFrame = new SKBitmap(width, height);

            var bytesPerPixel = currentFrame.BytesPerPixel;
            var totalSize = currentFrame.ByteCount;

            unsafe
            {
                byte* scan1 = (byte*)currentFrame.GetPixels().ToPointer();
                byte* scan2 = (byte*)previousFrame.GetPixels().ToPointer();
                byte* scan3 = (byte*)diffFrame.GetPixels().ToPointer();

                for (var row = 0; row < height; row++)
                {
                    for (var column = 0; column < width; column++)
                    {
                        var index = (row * width * bytesPerPixel) + (column * bytesPerPixel);

                        byte* data1 = scan1 + index;
                        byte* data2 = scan2 + index;
                        byte* data3 = scan3 + index;

                        if (data1[0] != data2[0] ||
                            data1[1] != data2[1] ||
                            data1[2] != data2[2] ||
                            data1[3] != data2[3])
                        {
                            anyChanges = true;
                            data3[0] = data2[0];
                            data3[1] = data2[1];
                            data3[2] = data2[2];
                            data3[3] = data2[3];
                        }

                    }
                }
            }

            if (anyChanges)
            {
                return Result.Ok(diffFrame);
            }

            diffFrame.Dispose();
            return Result.Fail<SKBitmap>("No difference found.");
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error while getting image diff.");
            return Result.Fail<SKBitmap>(ex);
        }
    }
    public SKRect GetDiffArea(SKBitmap currentFrame, SKBitmap? previousFrame, bool forceFullscreen = false)
    {
        try
        {
            if (currentFrame is null)
            {
                return SKRect.Empty;
            }

            if (previousFrame is null || forceFullscreen)
            {
                return currentFrame.ToRectangle();
            }


            if (currentFrame.Height != previousFrame.Height ||
                currentFrame.Width != previousFrame.Width ||
                currentFrame.BytesPerPixel != previousFrame.BytesPerPixel)
            {
                return SKRect.Empty;
            }

            var width = currentFrame.Width;
            var height = currentFrame.Height;
            int left = int.MaxValue;
            int top = int.MaxValue;
            int right = int.MinValue;
            int bottom = int.MinValue;

            var bytesPerPixel = currentFrame.BytesPerPixel;
            var totalSize = currentFrame.ByteCount;

            unsafe
            {
                byte* scan1 = (byte*)currentFrame.GetPixels().ToPointer();
                byte* scan2 = (byte*)previousFrame.GetPixels().ToPointer();

                for (var row = 0; row < height; row++)
                {
                    for (var column = 0; column < width; column++)
                    {
                        var index = (row * width * bytesPerPixel) + (column * bytesPerPixel);

                        byte* data1 = scan1 + index;
                        byte* data2 = scan2 + index;

                        if (data1[0] != data2[0] ||
                            data1[1] != data2[1] ||
                            data1[2] != data2[2])
                        {

                            if (row < top)
                            {
                                top = row;
                            }
                            if (row > bottom)
                            {
                                bottom = row;
                            }
                            if (column < left)
                            {
                                left = column;
                            }
                            if (column > right)
                            {
                                right = column;
                            }
                        }

                    }
                }

                // Check for valid bounding box.
                if (left <= right && top <= bottom)
                {
                    left = Math.Max(left - 2, 0);
                    top = Math.Max(top - 2, 0);
                    right = Math.Min(right + 2, width);
                    bottom = Math.Min(bottom + 2, height);
                    return new SKRect(left, top, right, bottom);
                }

                return SKRect.Empty;
            }
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error while getting area diff.");
            return SKRect.Empty;
        }
    }
}