How to read pixels in the four corners of BitmapSource?

Question

I have a .NET BitmapSource object. I would like to read the four pixels at the corners of the bitmap and check if they are all darker than white. How can i do this?

Edit: I would not mind converting this object to another type with a better API.

Answer 1

BitmapSource has a CopyPixels method that can be used to get one or more pixel values.

A helper method that receives a single pixel value at a given pixel coordinate may look like the one shown below. Please note that it may need to be expanded to support all necessary pixel formats.

public static Color GetPixelColor(BitmapSource bitmap, int x, int y) { Color color; var bytesPerPixel = (bitmap.Format.BitsPerPixel + 7) / 8; var bytes = new byte[bytesPerPixel]; var rect = new Int32Rect(x, y, 1, 1); bitmap.CopyPixels(rect, bytes, bytesPerPixel, 0); if (bitmap.Format == PixelFormats.Bgra32) { color = Color.FromArgb(bytes[3], bytes[2], bytes[1], bytes[0]); } else if (bitmap.Format == PixelFormats.Bgr32) { color = Color.FromRgb(bytes[2], bytes[1], bytes[0]); } // handle other required formats else { color = Colors.Black; } return color; } 

You would use a method like this:

 var topLeftColor = GetPixelColor(bitmap, 0, 0); var topRightColor = GetPixelColor(bitmap, bitmap.PixelWidth - 1, 0); var bottomLeftColor = GetPixelColor(bitmap, 0, bitmap.PixelHeight - 1); var bottomRightColor = GetPixelColor(bitmap, bitmap.PixelWidth - 1, bitmap.PixelHeight - 1);