Converting an image to grayscale in WinForms

A simple little helper static method to easily convert any image to its grayscale counterpart using older WinForms classes (System.Drawing namespace stuff).

public static Image ConvertToGrayscale(Image image)
{
	Image grayscaleImage = new Bitmap(image.Width, image.Height, image.PixelFormat);

	ImageAttributes attributes = new ImageAttributes();

	// Red should be converted to (R*.299)+(G*.587)+(B*.114)
	// Green should be converted to (R*.299)+(G*.587)+(B*.114)
	// Blue should be converted to (R*.299)+(G*.587)+(B*.114)
	// Alpha should stay the same.
	ColorMatrix grayscaleMatrix = new System.Drawing.Imaging.ColorMatrix(new float[][]{
		new float[] {0.299f, 0.299f, 0.299f, 0, 0},
		new float[] {0.587f, 0.587f, 0.587f, 0, 0},
		new float[] {0.114f, 0.114f, 0.114f, 0, 0},
		new float[] {     0,      0,      0, 1, 0},
		new float[] {     0,      0,      0, 0, 1}});
	attributes.SetColorMatrix(grayscaleMatrix);

	// Use a Graphics object from the new image
	using (Graphics graphics = Graphics.FromImage(grayscaleImage))
	{
		// Draw the original image using the ImageAttributes we created
		graphics.DrawImage(image,
			new Rectangle(0, 0, grayscaleImage.Width, grayscaleImage.Height),
			0, 0, grayscaleImage.Width, grayscaleImage.Height,
			GraphicsUnit.Pixel, attributes);
	}

	return grayscaleImage;
}

Note that the matrix I use is a fairly common one, but there are other ways depending on if you want a luminance-based or channel-based. It’s actually kinda interesting.