PNG_CMAP_GA_BACKGROUND 2317 pngread.c                  background_index = PNG_CMAP_GA_BACKGROUND;
PNG_CMAP_GA_BACKGROUND 2482 pngread.c                     background_index = PNG_CMAP_GA_BACKGROUND;
PNG_CMAP_GA_BACKGROUND 2847 pngread.c               if (background_index != PNG_CMAP_GA_BACKGROUND)