image/decoders/GIF2.h

   1 /* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #ifndef mozilla_image_decoders_GIF2_H
   7 #define mozilla_image_decoders_GIF2_H
   8
   9 #define MAX_LZW_BITS 12
  10 #define MAX_BITS 4097  // 2^MAX_LZW_BITS+1
  11 #define MAX_COLORS 256
  12 #define MIN_HOLD_SIZE 256
  13
  14 enum { GIF_TRAILER = 0x3B };               // ';'
  15 enum { GIF_IMAGE_SEPARATOR = 0x2C };       // ','
  16 enum { GIF_EXTENSION_INTRODUCER = 0x21 };  // '!'
  17 enum { GIF_GRAPHIC_CONTROL_LABEL = 0xF9 };
  18 enum { GIF_APPLICATION_EXTENSION_LABEL = 0xFF };
  19
  20 // A GIF decoder's state
  21 typedef struct gif_struct {
  22   // LZW decoder state machine
  23   uint8_t* stackp;  // Current stack pointer
  24   int datasize;
  25   int codesize;
  26   int codemask;
  27   int avail;  // Index of next available slot in dictionary
  28   int oldcode;
  29   uint8_t firstchar;
  30   int bits;       // Number of unread bits in "datum"
  31   int32_t datum;  // 32-bit input buffer
  32
  33   // Output state machine
  34   int64_t pixels_remaining;  // Pixels remaining to be output.
  35
  36   // Parameters for image frame currently being decoded
  37   int tpixel;                // Index of transparent pixel
  38   int32_t disposal_method;   // Restore to background, leave in place, etc.
  39   uint32_t* local_colormap;  // Per-image colormap
  40   uint32_t local_colormap_buffer_size;  // Size of the buffer containing the
  41                                         // local colormap.
  42   int local_colormap_size;              // Size of local colormap array.
  43   uint32_t delay_time;                  // Display time, in milliseconds,
  44                                         // for this image in a multi-image GIF
  45
  46   // Global (multi-image) state
  47   int version;           // Either 89 for GIF89 or 87 for GIF87
  48   int32_t screen_width;  // Logical screen width & height
  49   int32_t screen_height;
  50   uint8_t global_colormap_depth;   // Depth of global colormap array
  51   uint16_t global_colormap_count;  // Number of colors in global colormap
  52   int images_decoded;              // Counts images for multi-part GIFs
  53   int loop_count;  // Netscape specific extension block to control
  54                    // the number of animation loops a GIF
  55                    // renders.
  56
  57   bool is_transparent;  // TRUE, if tpixel is valid
  58
  59   uint16_t prefix[MAX_BITS];             // LZW decoding tables
  60   uint32_t global_colormap[MAX_COLORS];  // Default colormap if local not
  61                                          //   supplied
  62   uint8_t suffix[MAX_BITS];              // LZW decoding tables
  63   uint8_t stack[MAX_BITS];               // Base of LZW decoder stack
  64
  65 } gif_struct;
  66
  67 #endif  // mozilla_image_decoders_GIF2_H