vp8li_dec.h - mozsearch

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// Copyright 2012 Google Inc. All Rights Reserved.

//

// Use of this source code is governed by a BSD-style license

// that can be found in the COPYING file in the root of the source

// tree. An additional intellectual property rights grant can be found

// in the file PATENTS. All contributing project authors may

// be found in the AUTHORS file in the root of the source tree.

// -----------------------------------------------------------------------------

//

// Lossless decoder: internal header.

//

// Author: Skal (pascal.massimino@gmail.com)

//         Vikas Arora(vikaas.arora@gmail.com)

#ifndef WEBP_DEC_VP8LI_DEC_H_

#define WEBP_DEC_VP8LI_DEC_H_

#include <string.h>     // for memcpy()

#include "src/dec/webpi_dec.h"

#include "src/utils/bit_reader_utils.h"

#include "src/utils/color_cache_utils.h"

#include "src/utils/huffman_utils.h"

#include "src/webp/types.h"

#ifdef __cplusplus

extern "C" {

#endif

typedef enum {

  READ_DATA = 0,

  READ_HDR = 1,

  READ_DIM = 2

} VP8LDecodeState;

typedef struct VP8LTransform VP8LTransform;

struct VP8LTransform {

  VP8LImageTransformType type_;   // transform type.

  int                    bits_;   // subsampling bits defining transform window.

  int                    xsize_;  // transform window X index.

  int                    ysize_;  // transform window Y index.

  uint32_t*              data_;   // transform data.

};

typedef struct {

  int             color_cache_size_;

  VP8LColorCache  color_cache_;

  VP8LColorCache  saved_color_cache_;  // for incremental

  int             huffman_mask_;

  int             huffman_subsample_bits_;

  int             huffman_xsize_;

  uint32_t*       huffman_image_;

  int             num_htree_groups_;

  HTreeGroup*     htree_groups_;

  HuffmanTables   huffman_tables_;

} VP8LMetadata;

typedef struct VP8LDecoder VP8LDecoder;

struct VP8LDecoder {

  VP8StatusCode    status_;

  VP8LDecodeState  state_;

  VP8Io*           io_;

  const WebPDecBuffer* output_;    // shortcut to io->opaque->output

  uint32_t*        pixels_;        // Internal data: either uint8_t* for alpha

                                   // or uint32_t* for BGRA.

  uint32_t*        argb_cache_;    // Scratch buffer for temporary BGRA storage.

  VP8LBitReader    br_;

  int              incremental_;   // if true, incremental decoding is expected

  VP8LBitReader    saved_br_;      // note: could be local variables too

  int              saved_last_pixel_;

  int              width_;

  int              height_;

  int              last_row_;      // last input row decoded so far.

  int              last_pixel_;    // last pixel decoded so far. However, it may

                                   // not be transformed, scaled and

                                   // color-converted yet.

  int              last_out_row_;  // last row output so far.

  VP8LMetadata     hdr_;

  int              next_transform_;

  VP8LTransform    transforms_[NUM_TRANSFORMS];

  // or'd bitset storing the transforms types.

  uint32_t         transforms_seen_;

  uint8_t*         rescaler_memory;  // Working memory for rescaling work.

  WebPRescaler*    rescaler;         // Common rescaler for all channels.

};

//------------------------------------------------------------------------------

// internal functions. Not public.

struct ALPHDecoder;  // Defined in dec/alphai.h.

// in vp8l.c

// Decodes image header for alpha data stored using lossless compression.

// Returns false in case of error.

WEBP_NODISCARD int VP8LDecodeAlphaHeader(struct ALPHDecoder* const alph_dec,

                                         const uint8_t* const data,

                                         size_t data_size);

// Decodes *at least* 'last_row' rows of alpha. If some of the initial rows are

// already decoded in previous call(s), it will resume decoding from where it

// was paused.

// Returns false in case of bitstream error.

WEBP_NODISCARD int VP8LDecodeAlphaImageStream(

    struct ALPHDecoder* const alph_dec, int last_row);

// Allocates and initialize a new lossless decoder instance.

WEBP_NODISCARD VP8LDecoder* VP8LNew(void);

// Decodes the image header. Returns false in case of error.

WEBP_NODISCARD int VP8LDecodeHeader(VP8LDecoder* const dec, VP8Io* const io);

// Decodes an image. It's required to decode the lossless header before calling

// this function. Returns false in case of error, with updated dec->status_.

WEBP_NODISCARD int VP8LDecodeImage(VP8LDecoder* const dec);

// Resets the decoder in its initial state, reclaiming memory.

// Preserves the dec->status_ value.

void VP8LClear(VP8LDecoder* const dec);

// Clears and deallocate a lossless decoder instance.

void VP8LDelete(VP8LDecoder* const dec);

// Helper function for reading the different Huffman codes and storing them in

// 'huffman_tables' and 'htree_groups'.

// If mapping is NULL 'num_htree_groups_max' must equal 'num_htree_groups'.

// If it is not NULL, it maps 'num_htree_groups_max' indices to the

// 'num_htree_groups' groups. If 'num_htree_groups_max' > 'num_htree_groups',

// some of those indices map to -1. This is used for non-balanced codes to

// limit memory usage.

WEBP_NODISCARD int ReadHuffmanCodesHelper(

    int color_cache_bits, int num_htree_groups, int num_htree_groups_max,

    const int* const mapping, VP8LDecoder* const dec,

    HuffmanTables* const huffman_tables, HTreeGroup** const htree_groups);

//------------------------------------------------------------------------------

#ifdef __cplusplus

}    // extern "C"

#endif

#endif  // WEBP_DEC_VP8LI_DEC_H_