Renders an OpenCV frame via SkiaSharp.

SkiaVideoFrameRenderer

using System;
using System.Diagnostics;
using System.Text;
using Microsoft.Extensions.Primitives;
using Microsoft.Maui.ApplicationModel;
using OpenCvSharp;
using SkiaSharp;
using static System.Net.Mime.MediaTypeNames;

namespace MyApp
{
    public class SkiaVideoFrameRenderer : IDisposable
    {
        private int frameWidth;
        private int frameHeight;

        private object frameLock = new object();
        private Mat frame;
        private SKPaint paint;

        public SkiaVideoFrameRenderer()
        {
            paint = new SKPaint
            {
                IsAntialias = true,
                FilterQuality = SKFilterQuality.High
            };
        }

        byte[] frameBuffer;
        public void SetFrame(Mat frame, int width, int height)
        {
            lock (frameLock)
            {
                if (this.frame != null)
                {
                    if (this.frame.IsDisposed == false)
                    {
                        this.frame.Release();
                        this.frame.Dispose();
                    }
                    this.frame = null;
                }
                this.frame = frame;

                if (frame != null)
                {
                    framesReceived++;
                }

                if (frame == null)
                {
                    frameBuffer = null;
                }

                if (width != this.frameWidth || height != this.frameHeight)
                {
                    frameBuffer = new byte[width * height * 4];
                }
                frameWidth = width;
                frameHeight = height;
            }
        }

        public void RenderFrame(SKRectI canvasRect, SKCanvas canvas)
        {
            lock (frameLock)
            {
                if (this.frame == null || frameBuffer == null)
                {
                    return;
                }

                VideoFrameDecoderHelper.DecodeInto(this.frame, ref frameBuffer);

                canvas.Clear(SKColors.Black);

                unsafe
                {
                    var size = SkiaHelpers.ResizeKeepAspect(frameWidth, frameHeight, canvasRect.Width, canvasRect.Height);
                    // The following code block performs a buffer copy of the open CV frame using pointer dereferencing (rather than C#'s array derefencing operator).
                    // This code AOT compiles in release mode and will run 30x-60x faster than in debug mode.
                    // Debug mode may be 50-60ms, release may be between 1-2ms.
                    fixed (byte* framePointer = &frameBuffer[0])
                    {
                        var imageInfo = new SKImageInfo(frameWidth, frameHeight, SKColorType.Rgba8888);
                        using (var image = SKImage.FromPixels(imageInfo, (IntPtr)framePointer))
                        {
                            var rect = SkiaHelpers.GetCenteredRect(canvasRect, size);
                            canvas.DrawImage(image, rect, paint);
                        }
                    }
                }
            }
        }

        public void Dispose()
        {
            if (paint != null)
            {
                paint.Dispose();
                paint = null;
            }

            if (this.frame != null)
            {
                if (this.frame.IsDisposed == false)
                {
                    this.frame.Release();
                    this.frame.Dispose();
                }
                this.frame = null;
            }
        }
    }
}