# Copy the pixel data into a new `CByteArray`
#
# If `pad_to_pow2` the new buffer contains artificial pixels used to make
- # the width and the height powers of 2 for compatibility with OpenGL.
- fun copy_pixels(pad_to_pow2: nullable Bool): CByteArray
+ # the width and the height powers of 2 for compatibility with older OpenGL.
+ #
+ # If `unmultiply`, extra work is done to revert the multiplication of color
+ # values per the alpha channel applied by the Android system.
+ fun copy_pixels(pad_to_pow2, unmultiply: nullable Bool): CByteArray
do
var height = height
var row_bytes = row_bytes
var java_buf = buf.to_java_nio_buffer
copy_pixels_to_buffer java_buf
+ if has_alpha and unmultiply == true then buf.native_array.unmultiply(width, height)
+
if pad_to_pow2 == true then
for r in [height-1..0[.step(-1) do
var src_offset = row_bytes*r
var dst_offset = row_bytes2*r
- buf.memmove(dst_offset, src_offset, row_bytes)
+ buf.move(dst_offset, src_offset, row_bytes)
end
end
return p
end
end
+
+redef class NativeCByteArray
+ # Reverse Android multiplication of color values per the alpha channel
+ private fun unmultiply(w, h: Int) `{
+ int offset = 0;
+ int x, y;
+ for (x = 0; x < w; x ++)
+ for (y = 0; y < h; y ++) {
+ unsigned char a = self[offset+3];
+ if (a != 0 && a != 0xFF) {
+ self[offset] = self[offset] * 256 / a;
+ self[offset+1] = self[offset+1] * 256 / a;
+ self[offset+2] = self[offset+2] * 256 / a;
+ }
+ offset += 4;
+ }
+ `}
+end