1 // Copyright 2011 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 // Author: Jyrki Alakuijala (jyrki (at) google.com) 9 // 10 // Entropy encoding (Huffman) for webp lossless 11 12 #ifndef WEBP_UTILS_HUFFMAN_ENCODE_H_ 13 #define WEBP_UTILS_HUFFMAN_ENCODE_H_ 14 15 #include "webp/types.h" 16 17 #if defined(__cplusplus) || defined(c_plusplus) 18 extern "C" { 19 #endif 20 21 // Struct for holding the tree header in coded form. 22 typedef struct { 23 uint8_t code; // value (0..15) or escape code (16,17,18) 24 uint8_t extra_bits; // extra bits for escape codes 25 } HuffmanTreeToken; 26 27 // Struct to represent the tree codes (depth and bits array). 28 typedef struct { 29 int num_symbols; // Number of symbols. 30 uint8_t* code_lengths; // Code lengths of the symbols. 31 uint16_t* codes; // Symbol Codes. 32 } HuffmanTreeCode; 33 34 // Turn the Huffman tree into a token sequence. 35 // Returns the number of tokens used. 36 int VP8LCreateCompressedHuffmanTree(const HuffmanTreeCode* const tree, 37 HuffmanTreeToken* tokens, int max_tokens); 38 39 // Create an optimized tree, and tokenize it. 40 int VP8LCreateHuffmanTree(int* const histogram, int tree_depth_limit, 41 HuffmanTreeCode* const tree); 42 43 #if defined(__cplusplus) || defined(c_plusplus) 44 } 45 #endif 46 47 #endif // WEBP_UTILS_HUFFMAN_ENCODE_H_ 48
