Home | History | Annotate | Download | only in dec 
      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 
     24 #ifdef __cplusplus
     25 extern "C" {
     26 #endif
     27 
     28 typedef enum {
     29   READ_DATA = 0,
     30   READ_HDR = 1,
     31   READ_DIM = 2
     32 } VP8LDecodeState;
     33 
     34 typedef struct VP8LTransform VP8LTransform;
     35 struct VP8LTransform {
     36   VP8LImageTransformType type_;   // transform type.
     37   int                    bits_;   // subsampling bits defining transform window.
     38   int                    xsize_;  // transform window X index.
     39   int                    ysize_;  // transform window Y index.
     40   uint32_t              *data_;   // transform data.
     41 };
     42 
     43 typedef struct {
     44   int             color_cache_size_;
     45   VP8LColorCache  color_cache_;
     46 
     47   int             huffman_mask_;
     48   int             huffman_subsample_bits_;
     49   int             huffman_xsize_;
     50   uint32_t       *huffman_image_;
     51   int             num_htree_groups_;
     52   HTreeGroup     *htree_groups_;
     53 } VP8LMetadata;
     54 
     55 typedef struct VP8LDecoder VP8LDecoder;
     56 struct VP8LDecoder {
     57   VP8StatusCode    status_;
     58   VP8LDecodeState  action_;
     59   VP8LDecodeState  state_;
     60   VP8Io           *io_;
     61 
     62   const WebPDecBuffer *output_;    // shortcut to io->opaque->output
     63 
     64   uint32_t        *pixels_;        // Internal data: either uint8_t* for alpha
     65                                    // or uint32_t* for BGRA.
     66   uint32_t        *argb_cache_;    // Scratch buffer for temporary BGRA storage.
     67 
     68   VP8LBitReader    br_;
     69 
     70   int              width_;
     71   int              height_;
     72   int              last_row_;      // last input row decoded so far.
     73   int              last_pixel_;    // last pixel decoded so far. However, it may
     74                                    // not be transformed, scaled and
     75                                    // color-converted yet.
     76   int              last_out_row_;  // last row output so far.
     77 
     78   VP8LMetadata     hdr_;
     79 
     80   int              next_transform_;
     81   VP8LTransform    transforms_[NUM_TRANSFORMS];
     82   // or'd bitset storing the transforms types.
     83   uint32_t         transforms_seen_;
     84 
     85   uint8_t         *rescaler_memory;  // Working memory for rescaling work.
     86   WebPRescaler    *rescaler;         // Common rescaler for all channels.
     87 };
     88 
     89 //------------------------------------------------------------------------------
     90 // internal functions. Not public.
     91 
     92 struct ALPHDecoder;  // Defined in dec/alphai.h.
     93 
     94 // in vp8l.c
     95 
     96 // Decodes image header for alpha data stored using lossless compression.
     97 // Returns false in case of error.
     98 int VP8LDecodeAlphaHeader(struct ALPHDecoder* const alph_dec,
     99                           const uint8_t* const data, size_t data_size,
    100                           uint8_t* const output);
    101 
    102 // Decodes *at least* 'last_row' rows of alpha. If some of the initial rows are
    103 // already decoded in previous call(s), it will resume decoding from where it
    104 // was paused.
    105 // Returns false in case of bitstream error.
    106 int VP8LDecodeAlphaImageStream(struct ALPHDecoder* const alph_dec,
    107                                int last_row);
    108 
    109 // Allocates and initialize a new lossless decoder instance.
    110 VP8LDecoder* VP8LNew(void);
    111 
    112 // Decodes the image header. Returns false in case of error.
    113 int VP8LDecodeHeader(VP8LDecoder* const dec, VP8Io* const io);
    114 
    115 // Decodes an image. It's required to decode the lossless header before calling
    116 // this function. Returns false in case of error, with updated dec->status_.
    117 int VP8LDecodeImage(VP8LDecoder* const dec);
    118 
    119 // Resets the decoder in its initial state, reclaiming memory.
    120 // Preserves the dec->status_ value.
    121 void VP8LClear(VP8LDecoder* const dec);
    122 
    123 // Clears and deallocate a lossless decoder instance.
    124 void VP8LDelete(VP8LDecoder* const dec);
    125 
    126 //------------------------------------------------------------------------------
    127 
    128 #ifdef __cplusplus
    129 }    // extern "C"
    130 #endif
    131 
    132 #endif  /* WEBP_DEC_VP8LI_H_ */
    133