Image to Image from .net bitmap

[nigelianburton]

Thanks for bringing Stable Diffusion to .NET. The library includes helpers to convert TextToImage output into a .NET bitmap image, but I can't see any way to run ImageToImage from a .NET bitmap. Did I miss it/is it something you plan?

[DarthAffe]

Since System.Drawing is windows only, .NET bitmaps will not be supported directly in the "core"-library. I'm planning on adding more helper for image handling and conversion as additional packages though, but this will take some more time.

Until then you can use this extension:

public static unsafe Image<ColorRGB> ToImage(this Bitmap bitmap)
{
    int width = bitmap.Width;
    int height = bitmap.Height;

    byte[] buffer = new byte[height * width * ColorRGB.ColorFormat.BytesPerPixel];
    Span<ColorRGB> colorBuffer = MemoryMarshal.Cast<byte, ColorRGB>(buffer);

    Rectangle rect = new(0, 0, bitmap.Width, bitmap.Height);
    BitmapData bmpData = bitmap.LockBits(rect, ImageLockMode.ReadOnly, bitmap.PixelFormat);

    nint ptr = bmpData.Scan0;
    for (int y = 0; y < height; y++)
    {
        Span<ColorBGR> source = new((void*)ptr, bmpData.Stride);
        Span<ColorRGB> target = colorBuffer.Slice(y * width, width);
        for (int x = 0; x < width; x++)
        {
            ColorBGR srcColor = source[x];
            target[x] = new ColorRGB(srcColor.R, srcColor.G, srcColor.B);
        }

        ptr += bmpData.Stride;
    }

    bitmap.UnlockBits(bmpData);

    return new Image<ColorRGB>(buffer, 0, 0, width, height, width);
}

and then call it like this:

using Bitmap bitmap = new(@"<path to image>");
Image<ColorRGB> sourceImage = bitmap.ToImage();
            
using StableDiffusionImage image = model.ImageToImage("<prompt>", sourceImage.ToArray(), new StableDiffusionParameter());

Overall this is not an ideal solution in terms of performance and usability but I should work for now ~