github.com/cellofellow/gopkg@v0.0.0-20140722061823-eec0544a62ad/image/webp/libwebp/src/utils/huffman_encode.h (about)

     1  // Copyright 2011 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  // Author: Jyrki Alakuijala (jyrki@google.com)
    11  //
    12  // Entropy encoding (Huffman) for webp lossless
    13  
    14  #ifndef WEBP_UTILS_HUFFMAN_ENCODE_H_
    15  #define WEBP_UTILS_HUFFMAN_ENCODE_H_
    16  
    17  #include "../webp/types.h"
    18  
    19  #ifdef __cplusplus
    20  extern "C" {
    21  #endif
    22  
    23  // Struct for holding the tree header in coded form.
    24  typedef struct {
    25    uint8_t code;         // value (0..15) or escape code (16,17,18)
    26    uint8_t extra_bits;   // extra bits for escape codes
    27  } HuffmanTreeToken;
    28  
    29  // Struct to represent the tree codes (depth and bits array).
    30  typedef struct {
    31    int       num_symbols;   // Number of symbols.
    32    uint8_t*  code_lengths;  // Code lengths of the symbols.
    33    uint16_t* codes;         // Symbol Codes.
    34  } HuffmanTreeCode;
    35  
    36  // Turn the Huffman tree into a token sequence.
    37  // Returns the number of tokens used.
    38  int VP8LCreateCompressedHuffmanTree(const HuffmanTreeCode* const tree,
    39                                      HuffmanTreeToken* tokens, int max_tokens);
    40  
    41  // Create an optimized tree, and tokenize it.
    42  int VP8LCreateHuffmanTree(int* const histogram, int tree_depth_limit,
    43                            HuffmanTreeCode* const tree);
    44  
    45  #ifdef __cplusplus
    46  }
    47  #endif
    48  
    49  #endif  // WEBP_UTILS_HUFFMAN_ENCODE_H_