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