ImageStatisticsYCbCr Constructor (Bitmap, Bitmap)
|Source pixel format is not supported.
|Mask image must be 8 bpp grayscale image.
|Mask must have the same size as the source image to get statistics for.
The mask image must be a grayscale/binary (8bpp) image of the same size as the specified source image, where black pixels (value 0) correspond to areas which should be excluded from processing. So statistics is calculated only for pixels, which are none black in the mask image.