Drawing Pixels in WPF

Question

how would I manage pixel-by-pixel rendering in WPF (like, say, for a raytracer)? My initial guess was to create a BitmapImage, modify the buffer, and display that in an Imag

Answer 1

Here's a method using WritableBitmap.

public void DrawRectangle(WriteableBitmap writeableBitmap, int left, int top, int width, int height, Color color)
{
    // Compute the pixel's color
    int colorData = color.R << 16; // R
    colorData |= color.G << 8; // G
    colorData |= color.B << 0; // B
    int bpp = writeableBitmap.Format.BitsPerPixel / 8;

    unsafe
    {
        for (int y = 0; y < height; y++)
        {
            // Get a pointer to the back buffer
            int pBackBuffer = (int)writeableBitmap.BackBuffer;

            // Find the address of the pixel to draw
            pBackBuffer += (top + y) * writeableBitmap.BackBufferStride;
            pBackBuffer += left * bpp;

            for (int x = 0; x < width; x++)
            {
                // Assign the color data to the pixel
                *((int*)pBackBuffer) = colorData;

                // Increment the address of the pixel to draw
                pBackBuffer += bpp;
            }
        }
    }

    writeableBitmap.AddDirtyRect(new Int32Rect(left, top, width, height));
}

And to use it:

private WriteableBitmap bitmap = new WriteableBitmap(1100, 1100, 96d, 96d, PixelFormats.Bgr24, null);

private void Button_Click(object sender, RoutedEventArgs e)
{
    int size = 10;

    Random rnd = new Random(DateTime.Now.Millisecond);
    bitmap.Lock(); // Lock() and Unlock() could be moved to the DrawRectangle() method. Just do some performance tests.

    for (int y = 0; y < 99; y++)
    {
        for (int x = 0; x < 99; x++)
        {
            byte colR = (byte)rnd.Next(256);
            byte colG = (byte)rnd.Next(256);
            byte colB = (byte)rnd.Next(256);

            DrawRectangle(bitmap, (size + 1) * x, (size + 1) * y, size, size, Color.FromRgb(colR, colG, colB));
        }
    }

    bitmap.Unlock(); // Lock() and Unlock() could be moved to the DrawRectangle() method. Just do some performance tests.

  image.Source = bitmap; // This should be done only once
}