Convert from one PixelFormat to an other WPF

Question

I know this sounds trivial, but I currently have stuck.

I have images in various formats as input. Gray16,Gray8,Indexed8 and so on. What do I need is to covert them to RGB24 format, so far I've done this

public WriteableBitmap ConvertToRgb(WriteableBitmap source)
        {
            <-- create the new bitmap of the same width/height as the source with specific RGB24 format-->
            var newBitmap = new WriteableBitmap(source.PixelWidth, source.PixelHeight, source.DpiX, source.DpiY, PixelFormats.Rgb24, source.Palette);
            
            <-- create my pixel array -->
            byte[] pixels = new byte[
                        source.PixelHeight * source.PixelWidth *
                            source.Format.BitsPerPixel / 8];
            <-- copy my original pixels into the array) --> 
            source.CopyPixels(pixels, source.PixelWidth * source.Format.BitsPerPixel / 8, 0);
            <-- write the pixels into the new image --> 
            newBitmap.WritePixels(
                 new Int32Rect(0, 0, newBitmap.PixelWidth, newBitmap.PixelHeight),
                 pixels,
                 newBitmap.PixelWidth * newBitmap.Format.BitsPerPixel/8,
                 0);

            return newBitmap;
        }

This method throws an exception "Buffer size is not sufficient"

I guess it has to do something with one of my WritePixels parameters. But I have no idea what is the right size of the buffer. I couldn't find much documentation. Any help would be nice.

The method I'm using to convert is not definitive, if you know a better way of converting please let me know.

Answer 1

So after many attempts I found the answer.

  public WriteableBitmap ConvertToRgb(WriteableBitmap source)
        {
            var newBitmap = new WriteableBitmap(source.PixelWidth, source.PixelHeight, source.DpiX, source.DpiY, PixelFormats.Rgb24, null);

            byte[] pixels = new byte[
                        source.PixelHeight * source.PixelWidth *
                            source.Format.BitsPerPixel / 8];

            source.CopyPixels(pixels, source.PixelWidth * source.Format.BitsPerPixel / 8, 0);

            byte[] newPixels = new byte[newBitmap.PixelWidth * newBitmap.PixelHeight * newBitmap.Format.BitsPerPixel / 8];

            var pixelCounter = 0;
            var colorArray = source.Palette != null ? source.Palette.Colors.ToArray() : BitmapPalettes.Gray256.Colors.ToArray();

            foreach (var pixel in pixels)
            {
                newPixels[pixelCounter] = colorArray[pixel].R;
                pixelCounter++;
                newPixels[pixelCounter] = colorArray[pixel].G;
                pixelCounter++;
                newPixels[pixelCounter] = colorArray[pixel].B;
                pixelCounter++;
            }

            newBitmap.WritePixels(
                 new Int32Rect(0, 0, newBitmap.PixelWidth, newBitmap.PixelHeight),
                 newPixels,
                 newBitmap.PixelWidth * newBitmap.Format.BitsPerPixel / 8,
                 0);

            return newBitmap;
        }

Basically the problem was somwhere in the Stride I guess and the newPixel array dimensions. This is a fully working converting function.