lib/android: revert Android's multiplication of color values with alpha

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>

diff --git a/lib/android/load_image.nit b/lib/android/load_image.nit
index aa2684b..bcdfbf4 100644 (file)
--- a/lib/android/load_image.nit
+++ b/lib/android/load_image.nit
@@ -49,6 +49,8 @@ redef extern class NativeBitmap
                var java_buf = buf.to_java_nio_buffer
                copy_pixels_to_buffer java_buf
 
+               if has_alpha 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
@@ -77,3 +79,21 @@ redef universal Int
                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