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// Image transforms and color space conversion methods for lossless decoder. 11// 12// Authors: Vikas Arora (vikaas.arora@gmail.com) 13// Jyrki Alakuijala (jyrki@google.com) 14// Vincent Rabaud (vrabaud@google.com) 15 16#ifndef WEBP_DSP_LOSSLESS_COMMON_H_ 17#define WEBP_DSP_LOSSLESS_COMMON_H_ 18 19#include "src/webp/types.h" 20 21#include "src/utils/utils.h" 22 23#ifdef __cplusplus 24extern "C" { 25#endif 26 27//------------------------------------------------------------------------------ 28// Decoding 29 30// color mapping related functions. 31static WEBP_INLINE uint32_t VP8GetARGBIndex(uint32_t idx) { 32 return (idx >> 8) & 0xff; 33} 34 35static WEBP_INLINE uint8_t VP8GetAlphaIndex(uint8_t idx) { 36 return idx; 37} 38 39static WEBP_INLINE uint32_t VP8GetARGBValue(uint32_t val) { 40 return val; 41} 42 43static WEBP_INLINE uint8_t VP8GetAlphaValue(uint32_t val) { 44 return (val >> 8) & 0xff; 45} 46 47//------------------------------------------------------------------------------ 48// Misc methods. 49 50// Computes sampled size of 'size' when sampling using 'sampling bits'. 51static WEBP_INLINE uint32_t VP8LSubSampleSize(uint32_t size, 52 uint32_t sampling_bits) { 53 return (size + (1 << sampling_bits) - 1) >> sampling_bits; 54} 55 56// Converts near lossless quality into max number of bits shaved off. 57static WEBP_INLINE int VP8LNearLosslessBits(int near_lossless_quality) { 58 // 100 -> 0 59 // 80..99 -> 1 60 // 60..79 -> 2 61 // 40..59 -> 3 62 // 20..39 -> 4 63 // 0..19 -> 5 64 return 5 - near_lossless_quality / 20; 65} 66 67// ----------------------------------------------------------------------------- 68// Faster logarithm for integers. Small values use a look-up table. 69 70// The threshold till approximate version of log_2 can be used. 71// Practically, we can get rid of the call to log() as the two values match to 72// very high degree (the ratio of these two is 0.99999x). 73// Keeping a high threshold for now. 74#define APPROX_LOG_WITH_CORRECTION_MAX 65536 75#define APPROX_LOG_MAX 4096 76#define LOG_2_RECIPROCAL 1.44269504088896338700465094007086 77#define LOG_LOOKUP_IDX_MAX 256 78extern const float kLog2Table[LOG_LOOKUP_IDX_MAX]; 79extern const float kSLog2Table[LOG_LOOKUP_IDX_MAX]; 80typedef float (*VP8LFastLog2SlowFunc)(uint32_t v); 81 82extern VP8LFastLog2SlowFunc VP8LFastLog2Slow; 83extern VP8LFastLog2SlowFunc VP8LFastSLog2Slow; 84 85static WEBP_INLINE float VP8LFastLog2(uint32_t v) { 86 return (v < LOG_LOOKUP_IDX_MAX) ? kLog2Table[v] : VP8LFastLog2Slow(v); 87} 88// Fast calculation of v * log2(v) for integer input. 89static WEBP_INLINE float VP8LFastSLog2(uint32_t v) { 90 return (v < LOG_LOOKUP_IDX_MAX) ? kSLog2Table[v] : VP8LFastSLog2Slow(v); 91} 92 93// ----------------------------------------------------------------------------- 94// PrefixEncode() 95 96// Splitting of distance and length codes into prefixes and 97// extra bits. The prefixes are encoded with an entropy code 98// while the extra bits are stored just as normal bits. 99static WEBP_INLINE void VP8LPrefixEncodeBitsNoLUT(int distance, int* const code, 100 int* const extra_bits) { 101 const int highest_bit = BitsLog2Floor(--distance); 102 const int second_highest_bit = (distance >> (highest_bit - 1)) & 1; 103 *extra_bits = highest_bit - 1; 104 *code = 2 * highest_bit + second_highest_bit; 105} 106 107static WEBP_INLINE void VP8LPrefixEncodeNoLUT(int distance, int* const code, 108 int* const extra_bits, 109 int* const extra_bits_value) { 110 const int highest_bit = BitsLog2Floor(--distance); 111 const int second_highest_bit = (distance >> (highest_bit - 1)) & 1; 112 *extra_bits = highest_bit - 1; 113 *extra_bits_value = distance & ((1 << *extra_bits) - 1); 114 *code = 2 * highest_bit + second_highest_bit; 115} 116 117#define PREFIX_LOOKUP_IDX_MAX 512 118typedef struct { 119 int8_t code_; 120 int8_t extra_bits_; 121} VP8LPrefixCode; 122 123// These tables are derived using VP8LPrefixEncodeNoLUT. 124extern const VP8LPrefixCode kPrefixEncodeCode[PREFIX_LOOKUP_IDX_MAX]; 125extern const uint8_t kPrefixEncodeExtraBitsValue[PREFIX_LOOKUP_IDX_MAX]; 126static WEBP_INLINE void VP8LPrefixEncodeBits(int distance, int* const code, 127 int* const extra_bits) { 128 if (distance < PREFIX_LOOKUP_IDX_MAX) { 129 const VP8LPrefixCode prefix_code = kPrefixEncodeCode[distance]; 130 *code = prefix_code.code_; 131 *extra_bits = prefix_code.extra_bits_; 132 } else { 133 VP8LPrefixEncodeBitsNoLUT(distance, code, extra_bits); 134 } 135} 136 137static WEBP_INLINE void VP8LPrefixEncode(int distance, int* const code, 138 int* const extra_bits, 139 int* const extra_bits_value) { 140 if (distance < PREFIX_LOOKUP_IDX_MAX) { 141 const VP8LPrefixCode prefix_code = kPrefixEncodeCode[distance]; 142 *code = prefix_code.code_; 143 *extra_bits = prefix_code.extra_bits_; 144 *extra_bits_value = kPrefixEncodeExtraBitsValue[distance]; 145 } else { 146 VP8LPrefixEncodeNoLUT(distance, code, extra_bits, extra_bits_value); 147 } 148} 149 150// Sum of each component, mod 256. 151static WEBP_UBSAN_IGNORE_UNSIGNED_OVERFLOW WEBP_INLINE 152uint32_t VP8LAddPixels(uint32_t a, uint32_t b) { 153 const uint32_t alpha_and_green = (a & 0xff00ff00u) + (b & 0xff00ff00u); 154 const uint32_t red_and_blue = (a & 0x00ff00ffu) + (b & 0x00ff00ffu); 155 return (alpha_and_green & 0xff00ff00u) | (red_and_blue & 0x00ff00ffu); 156} 157 158// Difference of each component, mod 256. 159static WEBP_UBSAN_IGNORE_UNSIGNED_OVERFLOW WEBP_INLINE 160uint32_t VP8LSubPixels(uint32_t a, uint32_t b) { 161 const uint32_t alpha_and_green = 162 0x00ff00ffu + (a & 0xff00ff00u) - (b & 0xff00ff00u); 163 const uint32_t red_and_blue = 164 0xff00ff00u + (a & 0x00ff00ffu) - (b & 0x00ff00ffu); 165 return (alpha_and_green & 0xff00ff00u) | (red_and_blue & 0x00ff00ffu); 166} 167 168//------------------------------------------------------------------------------ 169// Transform-related functions use din both encoding and decoding. 170 171// Macros used to create a batch predictor that iteratively uses a 172// one-pixel predictor. 173 174// The predictor is added to the output pixel (which 175// is therefore considered as a residual) to get the final prediction. 176#define GENERATE_PREDICTOR_ADD(PREDICTOR, PREDICTOR_ADD) \ 177static void PREDICTOR_ADD(const uint32_t* in, const uint32_t* upper, \ 178 int num_pixels, uint32_t* out) { \ 179 int x; \ 180 for (x = 0; x < num_pixels; ++x) { \ 181 const uint32_t pred = (PREDICTOR)(out[x - 1], upper + x); \ 182 out[x] = VP8LAddPixels(in[x], pred); \ 183 } \ 184} 185 186// It subtracts the prediction from the input pixel and stores the residual 187// in the output pixel. 188#define GENERATE_PREDICTOR_SUB(PREDICTOR, PREDICTOR_SUB) \ 189static void PREDICTOR_SUB(const uint32_t* in, const uint32_t* upper, \ 190 int num_pixels, uint32_t* out) { \ 191 int x; \ 192 for (x = 0; x < num_pixels; ++x) { \ 193 const uint32_t pred = (PREDICTOR)(in[x - 1], upper + x); \ 194 out[x] = VP8LSubPixels(in[x], pred); \ 195 } \ 196} 197 198#ifdef __cplusplus 199} // extern "C" 200#endif 201 202#endif // WEBP_DSP_LOSSLESS_COMMON_H_ 203