PNG_FILLER_BEFORE  961 example.c         png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE);
PNG_FILLER_BEFORE 3818 pngread.c                        where = PNG_FILLER_BEFORE;
PNG_FILLER_BEFORE 1618 pngwrite.c              png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE);