freezy / wpf-skia-opengl

Proof of concept using Skia with WPF without WindowsFormsHost

WPF + Skia + OpenGL

A proof-of-concept of a GPU-accelerated surface without using WindowsFormsHost

Idea

Create a GL context manually, render all the compute-intensive stuff on an off-screen surface, and draw the result on a WPF-compatible control (in this case SKElement).

Why

SkiaSharp's examples use a WindowsFormsHost control for GPU-accelerated rendering, which uses OpenTK.

There are however a few issues with WindowsFormsHost:

• A window with AllowsTransparency enabled shows no controls - no transparency possible
• Given we can't do AllowsTransparency, setting WindowStyle to None still shows a border
• Airspace problems - things like context menus or DragMove don't work over a forms host

How

Instead of using OpenTK, we're creating a GL context through native calls on opengl32.dll. This code has already been provided in SkiaSharp's test suite:

_glContext = new WglContext();
_glContext.MakeCurrent();

Then, we initialize an offscreen surface as usual:

_grContext = GRContext.Create(GRBackend.OpenGL);
_surface = SKSurface.Create(_grContext, true, new SKImageInfo(width, height));

After drawing on the surface's canvas, we draw the result back on SKElement' canvas:

canvas.DrawSurface(_surface, new SKPoint(0f, 0f));

The surface is disposed and recreated when the SKElement's size changes.

wpf-skia-opengl's Issues

Can it be used to render images from the Geb.Image library?

Hi, currently I have the following code to render images from ImageBgr24 from Geb.Image library

XAML:

 <ContentControl Content="{Binding VideoDisplay}" />

Code behind:

       private VideoDisplay _videoDisplay;

       public VideoDisplay VideoDisplay { get => _videoDisplay; set { SetProperty(ref _videoDisplay, value); } }

        private ImageBgr24 imgCache;

        private WriteableBitmap bmpCache;

        public void OnRender(ImageBgr24 img)
        {
            if (img == null) return;
            if (imgCache == null) imgCache = img.Clone();
            lock (imgCache)
                imgCache.CloneFrom(img);
            VideoDisplay?.Dispatcher.InvokeAsync(Render);
        }

        private void Render()
        {
            if (bmpCache == null)
            {
                bmpCache = new WriteableBitmap(imgCache.Width, imgCache.Height, 96.0, 96.0, PixelFormats.Bgr24, null);
                VideoDisplay.RenderTarget.Source = bmpCache;
               //RenderTarget (Image) is a child control of VideoDisplay
            }
            lock (imgCache)
                bmpCache.WritePixels(new Int32Rect(0, 0, imgCache.Width, imgCache.Height), imgCache.StartIntPtr, imgCache.ByteCount, imgCache.Stride);
        }

My application will read frames from TCP Socket, then use Ffmpeg.AutoGen to decode to ImageBgr24 and call OnRender(ImageBgr24 img). Above code is responsible for updating ImageSource from ImageBgr24.

In my case is it possible to use wpf-skia-openg instead? A sample code is appreciated.
Thanks