uint8_t **bytestream, uint32_t *palette)
{
int i;
- unsigned int v;
+ unsigned int v, smallest_alpha = 0xFF, alpha_component = 0;
bytestream_put_buffer(bytestream, "GIF", 3);
bytestream_put_buffer(bytestream, "89a", 3);
for(i=0;i<256;i++) {
v = palette[i];
bytestream_put_be24(bytestream, v);
+ if (v >> 24 < smallest_alpha) {
+ smallest_alpha = v >> 24;
+ alpha_component = i;
+ }
+ }
+
+ if (smallest_alpha < 128) {
+ bytestream_put_byte(bytestream, 0x21); /* Extension Introducer */
+ bytestream_put_byte(bytestream, 0xf9); /* Graphic Control Label */
+ bytestream_put_byte(bytestream, 0x04); /* block length */
+ bytestream_put_byte(bytestream, 0x01); /* Transparent Color Flag */
+ bytestream_put_le16(bytestream, 0x00); /* no delay */
+ bytestream_put_byte(bytestream, alpha_component);
+ bytestream_put_byte(bytestream, 0x00);
}
return 0;