Retrieves the exact address of a pixel.
The address is determined according to the coordinates of a pixel, the pitch of the bitmap, and the bits per pixel.
For formats that have less than 8 bits per pixel, this method returns the address of the byte containing the pixel. For example, if your image format has 4 bits per pixel, GetPixelAddress returns the address of the first pixel in the byte, and you must calculate for 2 pixels per byte.
This method supports only DIB section bitmaps.