static int gif_read_header1(GifState *s) { ByteIOContext *f = s->f; uint8_t sig[6]; int ret, v, n; int has_global_palette; /* read gif signature */ ret = get_buffer(f, sig, 6); if (ret != 6) return -1; if (memcmp(sig, gif87a_sig, 6) != 0 && memcmp(sig, gif89a_sig, 6) != 0) return -1; /* read screen header */ s->transparent_color_index = -1; s->screen_width = get_le16(f); s->screen_height = get_le16(f); if( (unsigned)s->screen_width > 32767 || (unsigned)s->screen_height > 32767){ av_log(NULL, AV_LOG_ERROR, "picture size too large\n"); return -1; } v = get_byte(f); s->color_resolution = ((v & 0x70) >> 4) + 1; has_global_palette = (v & 0x80); s->bits_per_pixel = (v & 0x07) + 1; s->background_color_index = get_byte(f); get_byte(f); /* ignored */ #ifdef DEBUG printf("gif: screen_w=%d screen_h=%d bpp=%d global_palette=%d\n", s->screen_width, s->screen_height, s->bits_per_pixel, has_global_palette); #endif if (has_global_palette) { n = 1 << s->bits_per_pixel; get_buffer(f, s->global_palette, n * 3); } return 0; }