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      1 // Copyright 2012 Google Inc. All Rights Reserved.
      2 //
      3 // Use of this source code is governed by a BSD-style license
      4 // that can be found in the COPYING file in the root of the source
      5 // tree. An additional intellectual property rights grant can be found
      6 // in the file PATENTS. All contributing project authors may
      7 // be found in the AUTHORS file in the root of the source tree.
      8 // -----------------------------------------------------------------------------
      9 //
     10 // Lossless decoder: internal header.
     11 //
     12 // Author: Skal (pascal.massimino (at) gmail.com)
     13 //         Vikas Arora(vikaas.arora (at) gmail.com)
     14 
     15 #ifndef WEBP_DEC_VP8LI_H_
     16 #define WEBP_DEC_VP8LI_H_
     17 
     18 #include <string.h>     // for memcpy()
     19 #include "./webpi.h"
     20 #include "../utils/bit_reader.h"
     21 #include "../utils/color_cache.h"
     22 #include "../utils/huffman.h"
     23 #include "webp/format_constants.h"
     24 
     25 #if defined(__cplusplus) || defined(c_plusplus)
     26 extern "C" {
     27 #endif
     28 
     29 typedef enum {
     30   READ_DATA = 0,
     31   READ_HDR = 1,
     32   READ_DIM = 2
     33 } VP8LDecodeState;
     34 
     35 typedef struct VP8LTransform VP8LTransform;
     36 struct VP8LTransform {
     37   VP8LImageTransformType type_;   // transform type.
     38   int                    bits_;   // subsampling bits defining transform window.
     39   int                    xsize_;  // transform window X index.
     40   int                    ysize_;  // transform window Y index.
     41   uint32_t              *data_;   // transform data.
     42 };
     43 
     44 typedef struct {
     45   HuffmanTree htrees_[HUFFMAN_CODES_PER_META_CODE];
     46 } HTreeGroup;
     47 
     48 typedef struct {
     49   int             color_cache_size_;
     50   VP8LColorCache  color_cache_;
     51 
     52   int             huffman_mask_;
     53   int             huffman_subsample_bits_;
     54   int             huffman_xsize_;
     55   uint32_t       *huffman_image_;
     56   int             num_htree_groups_;
     57   HTreeGroup     *htree_groups_;
     58 } VP8LMetadata;
     59 
     60 typedef struct {
     61   VP8StatusCode    status_;
     62   VP8LDecodeState  action_;
     63   VP8LDecodeState  state_;
     64   VP8Io           *io_;
     65 
     66   const WebPDecBuffer *output_;    // shortcut to io->opaque->output
     67 
     68   uint32_t        *pixels_;        // Internal data: either uint8_t* for alpha
     69                                    // or uint32_t* for BGRA.
     70   uint32_t        *argb_cache_;    // Scratch buffer for temporary BGRA storage.
     71 
     72   VP8LBitReader    br_;
     73 
     74   int              width_;
     75   int              height_;
     76   int              last_row_;      // last input row decoded so far.
     77   int              last_out_row_;  // last row output so far.
     78 
     79   VP8LMetadata     hdr_;
     80 
     81   int              next_transform_;
     82   VP8LTransform    transforms_[NUM_TRANSFORMS];
     83   // or'd bitset storing the transforms types.
     84   uint32_t         transforms_seen_;
     85 
     86   uint8_t         *rescaler_memory;  // Working memory for rescaling work.
     87   WebPRescaler    *rescaler;         // Common rescaler for all channels.
     88 } VP8LDecoder;
     89 
     90 //------------------------------------------------------------------------------
     91 // internal functions. Not public.
     92 
     93 // in vp8l.c
     94 
     95 // Decodes a raw image stream (without header) and store the alpha data
     96 // into *output, which must be of size width x height. Returns false in case
     97 // of error.
     98 int VP8LDecodeAlphaImageStream(int width, int height, const uint8_t* const data,
     99                                size_t data_size, uint8_t* const output);
    100 
    101 // Allocates and initialize a new lossless decoder instance.
    102 VP8LDecoder* VP8LNew(void);
    103 
    104 // Decodes the image header. Returns false in case of error.
    105 int VP8LDecodeHeader(VP8LDecoder* const dec, VP8Io* const io);
    106 
    107 // Decodes an image. It's required to decode the lossless header before calling
    108 // this function. Returns false in case of error, with updated dec->status_.
    109 int VP8LDecodeImage(VP8LDecoder* const dec);
    110 
    111 // Resets the decoder in its initial state, reclaiming memory.
    112 // Preserves the dec->status_ value.
    113 void VP8LClear(VP8LDecoder* const dec);
    114 
    115 // Clears and deallocate a lossless decoder instance.
    116 void VP8LDelete(VP8LDecoder* const dec);
    117 
    118 //------------------------------------------------------------------------------
    119 
    120 #if defined(__cplusplus) || defined(c_plusplus)
    121 }    // extern "C"
    122 #endif
    123 
    124 #endif  /* WEBP_DEC_VP8LI_H_ */
    125