Remotely/Desktop.Core/Utilities/ImageUtils.cs

using SkiaSharp;
using SkiaSharp.Views.Desktop;
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace Remotely.Desktop.Core.Utilities
{
    public class ImageUtils
    {
        public static byte[] EncodeWithSkia(Bitmap bitmap, SKEncodedImageFormat format, int quality)
        {
            using var ms = new MemoryStream();
            var info = new SKImageInfo(bitmap.Width, bitmap.Height);
            var skBitmap = new SKBitmap(info);
            using (var pixmap = skBitmap.PeekPixels())
            {
                bitmap.ToSKPixmap(pixmap);
            }

            skBitmap.Encode(ms, format, quality);

            return ms.ToArray();
        }

        public static Rectangle GetDiffArea(Bitmap currentFrame, Bitmap previousFrame, bool captureFullscreen)
        {
            if (currentFrame == null || previousFrame == null)
            {
                return Rectangle.Empty;
            }

            if (captureFullscreen)
            {
                return new Rectangle(new Point(0, 0), currentFrame.Size);
            }
            if (currentFrame.Height != previousFrame.Height || currentFrame.Width != previousFrame.Width)
            {
                throw new Exception("Bitmaps are not of equal dimensions.");
            }
            if (currentFrame.PixelFormat != previousFrame.PixelFormat)
            {
                throw new Exception("Bitmaps are not the same format.");
            }
            var width = currentFrame.Width;
            var height = currentFrame.Height;
            int left = int.MaxValue;
            int top = int.MaxValue;
            int right = int.MinValue;
            int bottom = int.MinValue;

            BitmapData bd1 = null;
            BitmapData bd2 = null;

            try
            {
                bd1 = previousFrame.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadOnly, currentFrame.PixelFormat);
                bd2 = currentFrame.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadOnly, previousFrame.PixelFormat);

                var bytesPerPixel = Bitmap.GetPixelFormatSize(currentFrame.PixelFormat) / 8;
                var totalSize = bd1.Height * bd1.Width * bytesPerPixel;

                unsafe
                {
                    byte* scan1 = (byte*)bd1.Scan0.ToPointer();
                    byte* scan2 = (byte*)bd2.Scan0.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;
                                }
                            }

                        }
                    }

                    if (left <= right && top <= bottom)
                    {
                        // Bounding box is valid.  Padding is necessary to prevent artifacts from
                        // moving windows.
                        left = Math.Max(left - 5, 0);
                        top = Math.Max(top - 5, 0);
                        right = Math.Min(right + 5, width);
                        bottom = Math.Min(bottom + 5, height);

                        return new Rectangle(left, top, right - left, bottom - top);
                    }
                    else
                    {
                        return Rectangle.Empty;
                    }
                }
            }
            catch
            {
                return Rectangle.Empty;
            }
            finally
            {
                currentFrame.UnlockBits(bd1);
                previousFrame.UnlockBits(bd2);
            }
        }

        public static Bitmap GetImageDiff(Bitmap currentFrame, Bitmap previousFrame, bool captureFullscreen, out bool hadChanges)
        {
            hadChanges = false;
            if (currentFrame is null || previousFrame is null)
            {
                hadChanges = false;
                return null;
            }
            if (captureFullscreen)
            {
                hadChanges = true;
                return (Bitmap)currentFrame.Clone();
            }

            if (currentFrame.Height != previousFrame.Height || currentFrame.Width != previousFrame.Width)
            {
                throw new Exception("Bitmaps are not of equal dimensions.");
            }
            if (!Bitmap.IsAlphaPixelFormat(currentFrame.PixelFormat) || !Bitmap.IsAlphaPixelFormat(previousFrame.PixelFormat) ||
                !Bitmap.IsCanonicalPixelFormat(currentFrame.PixelFormat) || !Bitmap.IsCanonicalPixelFormat(previousFrame.PixelFormat))
            {
                throw new Exception("Bitmaps must be 32 bits per pixel and contain alpha channel.");
            }
            var width = currentFrame.Width;
            var height = currentFrame.Height;

            var mergedFrame = new Bitmap(width, height);

            var bd1 = previousFrame.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadOnly, currentFrame.PixelFormat);
            var bd2 = currentFrame.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadOnly, previousFrame.PixelFormat);
            var bd3 = mergedFrame.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.WriteOnly, currentFrame.PixelFormat);

            try
            {
                var bytesPerPixel = Bitmap.GetPixelFormatSize(currentFrame.PixelFormat) / 8;
                var totalSize = bd1.Height * bd1.Width * bytesPerPixel;

                unsafe
                {
                    byte* scan1 = (byte*)bd1.Scan0.ToPointer();
                    byte* scan2 = (byte*)bd2.Scan0.ToPointer();
                    byte* scan3 = (byte*)bd3.Scan0.ToPointer();

                    for (int counter = 0; counter < totalSize - bytesPerPixel; counter += bytesPerPixel)
                    {
                        byte* data1 = scan1 + counter;
                        byte* data2 = scan2 + counter;
                        byte* data3 = scan3 + counter;

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


                return mergedFrame;

            }
            catch
            {
                return mergedFrame;
            }
            finally
            {
                previousFrame.UnlockBits(bd1);
                currentFrame.UnlockBits(bd2);
                mergedFrame.UnlockBits(bd3);
            }
        }
    }
}