ImageSharp

[elijahr2411]

Hi! Do you have any pointers on getting your library to work with ImageSharp? I've read through the documentation and am honestly quite confused, it'd be great if you could help a bit. My goal is to, on each frame update, render the frame into an ImageSharp image for use with my program. Thanks!

[MarcusWichelmann]

Hi, interesting idea.
You could do that by implementing your own IRenderTarget. For that, please see the Readme and this Avalonia-specific sample implementation:
https://github.com/MarcusWichelmann/MarcusW.VncClient/blob/master/src/MarcusW.VncClient.Avalonia/RfbRenderTarget.cs#L31

You would only have to implement the GrabFramebufferReference method. As you can see, there it creates a WriteableBitmap, which is also Avalonia-specific, but could be any other Bitmap implementation. All the VNC-Client implementation needs, is a pointer to the memory, where whatever Bitmap implementation stores its image.

So after looking at the ImageSharp documentation, your best bet would probably be, to allocate your own byte[] rgbaBytes with the required size for all the pixels, return a IFramebufferReference with a pointer to that byte-array and then use the Dispose method of your `IFramebufferReference? implementation (see here) to pass the byte-array to ImageSharp using a callback when the rendering is finished:

using (var image = Image.LoadPixelData<Rgba32>(rgbaBytes, width, height))
{
    // Work with the image
}

Hope that helps.

[elijahr2411]

I'm a bit confused on how to implement that since it seems fixed pointers are only valid from within the fixed block

I also just tried using Marshal.Copy and got the same exception

[elijahr2411]

Figured it out, the problem was a bit stupid. I was only allocating enough bytes for 1 byte-per-pixel when I needed 4, causing the memory access violation.

[MarcusWichelmann]

I'm a bit confused on how to implement that since it seems fixed pointers are only valid from within the fixed block
Oh, you're right.

Great, that you found a fix.

[elijahr2411]

Hey, I've been working on this and have one more question. Do you know how I would detect the pixel format of the framebuffer? Because currently using PixelFormat.Plain gives this output.

This is what it should look like, for reference

[MarcusWichelmann]

Then you should create a new pixel format that matches, how ImageSharp expects the pixels to exist in memory. This should be visible from the ImageSharp documentation, or you just experiment a bit. Remember to think about little/big endiannes.