How to: Convert an Image to Grayscale
I ran across an issue where I wanted to convert an Image in a Windows Store app to grayscale and could not find a great example. So… here is one for you to try!
private async Task imageToGrayscale(Image src, Image dest)
{
RenderTargetBitmap renderTargetBitmap = new RenderTargetBitmap();
//Get existing src pixels in a Byte[] (always is BRGA formate
await renderTargetBitmap.RenderAsync(src);
IBuffer pixelSrc = await renderTargetBitmap.GetPixelsAsync();
Byte[] destBytes = new Byte[pixelSrc.Length];
for (int i = 0; i < pixelSrc.Length; i += 4)
{
double b = (double)pixelSrc.GetByte((uint)i) / 255.0;
double g = (double)pixelSrc.GetByte((uint)i+1) / 255.0;
double r = (double)pixelSrc.GetByte((uint)i+2) / 255.0;
byte a = pixelSrc.GetByte((uint)i + 3);
double e = (0.21 * r + 0.71 * g + 0.07 * b) * 255;
byte f = Convert.ToByte(e);
destBytes[i] = f;
destBytes[i + 1] = f;
destBytes[i + 2] = f;
destBytes[i + 3] = a;
}
WriteableBitmap destWB = new WriteableBitmap(renderTargetBitmap.PixelWidth, renderTargetBitmap.PixelHeight);
using (Stream pixelStream = destWB.PixelBuffer.AsStream()) {
pixelStream.Seek(0, SeekOrigin.Begin);
pixelStream.Write(destBytes, 0, destBytes.Length);
destWB.Invalidate();
}
destImage.Source = destWB;
}
If you like it, drop me a note of thanks!