set-argb-pixels in bitmap-dc%

Sets a rectangle of pixels in the bitmap, subject to the same rules and performance characteristics of set-pixel, except that the block set is likely to be faster than the sequence of individual sets.

• (send a-bitmap-dc set-argb-pixels x y width height pixels) -> void
     x : real number
     y : real number
     width : exact integer in [1, 10000]
     height : exact integer in [1, 10000]
     pixels : string

  The pixel RGB values are taken from pixels. The first character represents an alpha value that is currently ignored, the second character represents a red value to used for the pixel at (x, y), the third character is a blue value, etc. In this way, the first width*height*4 characters of pixels determine the new pixel values in the DC (except that alpha values are currently ignored). The pixels are in row-major order, left to right then top to bottom.