static int
read_logical_screen_descriptor(Gif_Stream *gfs, Gif_Reader *grr)
/* returns 0 on memory error */
{
uint8_t packed;
/* we don't care about logical screen width or height */
gfs->screen_width = gifgetunsigned(grr);
gfs->screen_height = gifgetunsigned(grr);
packed = gifgetbyte(grr);
gfs->background = gifgetbyte(grr);
/* don't care about pixel aspect ratio */
gifgetbyte(grr);
if (packed & 0x80) { /* have a global color table */
int ncol = 1 << ((packed & 0x07) + 1);
gfs->global = read_color_table(ncol, grr);
if (!gfs->global) return 0;
gfs->global->refcount = 1;
}
return 1;
}
static int
read_image(Gif_Reader *grr, Gif_Context *gfc, Gif_Image *gfi, int read_flags)
/* returns 0 on memory error */
{
uint8_t packed;
gfi->left = gifgetunsigned(grr);
gfi->top = gifgetunsigned(grr);
gfi->width = gifgetunsigned(grr);
gfi->height = gifgetunsigned(grr);
packed = gifgetbyte(grr);
GIF_DEBUG(("<%ux%u>", gfi->width, gfi->height));
if (packed & 0x80) { /* have a local color table */
int ncol = 1 << ((packed & 0x07) + 1);
gfi->local = read_color_table(ncol, grr);
if (!gfi->local) return 0;
gfi->local->refcount = 1;
}
gfi->interlace = (packed & 0x40) != 0;
/* Keep the compressed data if asked */
if (read_flags & GIF_READ_COMPRESSED) {
if (!read_compressed_image(gfi, grr, read_flags))
return 0;
if (read_flags & GIF_READ_UNCOMPRESSED) {
Gif_Reader new_grr;
make_data_reader(&new_grr, gfi->compressed, gfi->compressed_len);
if (!uncompress_image(gfc, gfi, &new_grr))
return 0;
}
} else if (read_flags & GIF_READ_UNCOMPRESSED) {
if (!uncompress_image(gfc, gfi, grr))
return 0;
} else {
/* skip over the image */
uint8_t buffer[GIF_MAX_BLOCK];
int i = gifgetbyte(grr);
while (i > 0) {
gifgetblock(buffer, i, grr);
i = gifgetbyte(grr);
}
}
return 1;
}
static void
read_graphic_control_extension(Gif_Context *gfc, Gif_Image *gfi,
Gif_Reader *grr)
{
uint8_t len;
uint8_t crap[GIF_MAX_BLOCK];
len = gifgetbyte(grr);
if (len == 4) {
uint8_t packed = gifgetbyte(grr);
gfi->disposal = (packed >> 2) & 0x07;
gfi->delay = gifgetunsigned(grr);
gfi->transparent = gifgetbyte(grr);
if (!(packed & 0x01)) /* transparent color doesn't exist */
gfi->transparent = -1;
len -= 4;
}
static int
read_image(Gif_Reader *grr, Gif_Context *gfc, Gif_Image *gfi, int read_flags)
/* returns 0 on memory error */
{
uint8_t packed;
gfi->left = gifgetunsigned(grr);
gfi->top = gifgetunsigned(grr);
gfi->width = gifgetunsigned(grr);
gfi->height = gifgetunsigned(grr);
/* Mainline GIF processors (Firefox, etc.) process missing width (height)
as screen_width (screen_height). */
if (gfi->width == 0)
gfi->width = gfc->stream->screen_width;
if (gfi->height == 0)
gfi->height = gfc->stream->screen_height;
/* If still zero, error. */
if (gfi->width == 0 || gfi->height == 0) {
gif_read_error(gfc, 1, "image has zero width and/or height");
Gif_MakeImageEmpty(gfi);
read_flags = 0;
}
/* If position out of range, error. */
if ((unsigned) gfi->left + (unsigned) gfi->width > 0xFFFF
|| (unsigned) gfi->top + (unsigned) gfi->height > 0xFFFF) {
gif_read_error(gfc, 1, "image position and/or dimensions out of range");
Gif_MakeImageEmpty(gfi);
read_flags = 0;
}
GIF_DEBUG(("<%ux%u>", gfi->width, gfi->height));
packed = gifgetbyte(grr);
if (packed & 0x80) { /* have a local color table */
int ncol = 1 << ((packed & 0x07) + 1);
gfi->local = read_color_table(ncol, grr);
if (!gfi->local) return 0;
gfi->local->refcount = 1;
}
gfi->interlace = (packed & 0x40) != 0;
/* Keep the compressed data if asked */
if (read_flags & GIF_READ_COMPRESSED) {
if (!read_compressed_image(gfi, grr, read_flags))
return 0;
if (read_flags & GIF_READ_UNCOMPRESSED) {
Gif_Reader new_grr;
make_data_reader(&new_grr, gfi->compressed, gfi->compressed_len);
if (!uncompress_image(gfc, gfi, &new_grr))
return 0;
}
} else if (read_flags & GIF_READ_UNCOMPRESSED) {
if (!uncompress_image(gfc, gfi, grr))
return 0;
} else {
/* skip over the image */
uint8_t buffer[GIF_MAX_BLOCK];
int i = gifgetbyte(grr);
while (i > 0) {
gifgetblock(buffer, i, grr);
i = gifgetbyte(grr);
}
}
return 1;
}