Skip to content
Permalink
Browse files

Date: Tue, 12 Aug 2003 14:26:19 +0200 (MEST)

From: "Mattias Engdeg?rd"
Subject: bug in SDL_GetRGB/GetRGBA

There's an embarrassing bug in GetRGB/GetRGBA which apparently has been there
for years. It incorrectly converts colours with < 8 bits/channel.
It came to my attention today in #sdl.

What it does now is (for each channel):

  rv = (pixel & fmt->Rmask) >> fmt->Rshift;
  *r = (rv << fmt->Rloss) + (rv >> (8 - fmt->Rloss));

which is wrong; the last line should be

  *r = (rv << fmt->Rloss) + (rv >> (8 - (fmt->Rloss << 1)));
  • Loading branch information
slouken committed Aug 12, 2003
1 parent 386eadf commit 909584009b14c5ddf5c19b228e024c3991277286
Showing with 7 additions and 7 deletions.
  1. +7 −7 src/video/SDL_pixels.c
@@ -381,14 +381,14 @@ void SDL_GetRGBA(Uint32 pixel, SDL_PixelFormat *fmt,
*/
unsigned v;
v = (pixel & fmt->Rmask) >> fmt->Rshift;
*r = (v << fmt->Rloss) + (v >> (8 - fmt->Rloss));
*r = (v << fmt->Rloss) + (v >> (8 - (fmt->Rloss << 1)));
v = (pixel & fmt->Gmask) >> fmt->Gshift;
*g = (v << fmt->Gloss) + (v >> (8 - fmt->Gloss));
*g = (v << fmt->Gloss) + (v >> (8 - (fmt->Gloss << 1)));
v = (pixel & fmt->Bmask) >> fmt->Bshift;
*b = (v << fmt->Bloss) + (v >> (8 - fmt->Bloss));
*b = (v << fmt->Bloss) + (v >> (8 - (fmt->Bloss << 1)));
if(fmt->Amask) {
v = (pixel & fmt->Amask) >> fmt->Ashift;
*a = (v << fmt->Aloss) + (v >> (8 - fmt->Aloss));
*a = (v << fmt->Aloss) + (v >> (8 - (fmt->Aloss << 1)));
} else
*a = SDL_ALPHA_OPAQUE;
} else {
@@ -405,11 +405,11 @@ void SDL_GetRGB(Uint32 pixel, SDL_PixelFormat *fmt, Uint8 *r,Uint8 *g,Uint8 *b)
/* the note for SDL_GetRGBA above applies here too */
unsigned v;
v = (pixel & fmt->Rmask) >> fmt->Rshift;
*r = (v << fmt->Rloss) + (v >> (8 - fmt->Rloss));
*r = (v << fmt->Rloss) + (v >> (8 - (fmt->Rloss << 1)));
v = (pixel & fmt->Gmask) >> fmt->Gshift;
*g = (v << fmt->Gloss) + (v >> (8 - fmt->Gloss));
*g = (v << fmt->Gloss) + (v >> (8 - (fmt->Gloss << 1)));
v = (pixel & fmt->Bmask) >> fmt->Bshift;
*b = (v << fmt->Bloss) + (v >> (8 - fmt->Bloss));
*b = (v << fmt->Bloss) + (v >> (8 - (fmt->Bloss << 1)));
} else {
*r = fmt->palette->colors[pixel].r;
*g = fmt->palette->colors[pixel].g;

0 comments on commit 9095840

Please sign in to comment.