I'm trying to convert some C# code into a shader so that I can get better performance. What my code does is look at the final scene rendered and average out the colors every (for example) 16x8 block of pixels. I've tried for 3 days to get this code working in a shader but I cannot figure it out. Shaders are really beyond me and there doesn't seem to be any up-to-date examples that I can hack together (which is all I could really do)

I did try to use two rendertargets, render the full scene then render it to a smaller target to force a resize. But I ended up losing too much clarity and it doesn't look as good as hand calculating the averages. I think this is because my average code doesn't assume the block area is square, which a resize would.

Can someone help me? Here is my C# code:

private void TranslateImageToTextSurface2(Texture2D image, TextSurface surface)
{
    surface.Clear();
    image.GetData<Color>(pixels);

    // surface.Font.Size represents the size of blocks in pixels.

    for (int h = 0; h < image.Height / surface.Font.Size.Y; h++)
    {
        int startY = (h * surface.Font.Size.Y);
        
        for (int w = 0; w < image.Width / surface.Font.Size.X; w++)
        {
            int startX = (w * surface.Font.Size.X);

            float allR = 0;
            float allG = 0;
            float allB = 0;
            for (int y = 0; y < surface.Font.Size.Y; y++)
            {
                for (int x = 0; x < surface.Font.Size.X; x++)
                {
                    int cY = y + startY;
                    int cX = x + startX;

                    Color color = pixels[cY * image.Width + cX];

                    allR += color.R;
                    allG += color.G;
                    allB += color.B;
                    //allBri += color.GetBrightness();
                }
            }

            // This only works for square fonts... ack??
            byte sr = (byte)(allR / (surface.Font.Size.X * surface.Font.Size.Y));
            byte sg = (byte)(allG / (surface.Font.Size.X * surface.Font.Size.Y));
            byte sb = (byte)(allB / (surface.Font.Size.X * surface.Font.Size.Y));

            var newColor = new Color(sr, sg, sb);

            // HERE IS WHERE I WOULD ADD PROCESS THAT AVG COLOR IN MY GAME ENGINE
        }
    }
}

Here is an example of what I end up out putting just using my code above versus forced resized through two render targets.

Hi Phil! I really appreciate the reply.

The only shader code I have is basic "render the exact pixel" everything I try never turns out near to what I'm looking for. When I get home I'll post what I have but it's a giant mess of commented code and trying different things.

I don't post my code of what I'm doing with those colors because it's not really important. What I do is a bunch of custom code that writes the color (and character based on brightness of that color) to my ascii game engine (http://github.com/thraka/sadconsole) which is rendered to the screen.

You are correct, the only output I need from the shader is the same output from my C# code. A single pixel per block.

The 16 and 8 values could really be anything. 16x16, or 8x16, even 4x2...