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/dsp/cpu.h"
20 #include "src/utils/utils.h"
21 #include "src/webp/types.h"
22
23 #ifdef __cplusplus
24 extern "C" {
25 #endif
26
27 //------------------------------------------------------------------------------
28 // Decoding
29
30 // color mapping related functions.
VP8GetARGBIndex(uint32_t idx)31 static WEBP_INLINE uint32_t VP8GetARGBIndex(uint32_t idx) {
32 return (idx >> 8) & 0xff;
33 }
34
VP8GetAlphaIndex(uint8_t idx)35 static WEBP_INLINE uint8_t VP8GetAlphaIndex(uint8_t idx) {
36 return idx;
37 }
38
VP8GetARGBValue(uint32_t val)39 static WEBP_INLINE uint32_t VP8GetARGBValue(uint32_t val) {
40 return val;
41 }
42
VP8GetAlphaValue(uint32_t val)43 static 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'.
VP8LSubSampleSize(uint32_t size,uint32_t sampling_bits)51 static 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.
VP8LNearLosslessBits(int near_lossless_quality)57 static 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 // VP8LFastLog2 and VP8LFastSLog2 are used on elements from image histograms.
77 // The histogram values cannot exceed the maximum number of pixels, which
78 // is (1 << 14) * (1 << 14). Therefore S * log(S) < (1 << 33).
79 // No more than 32 bits of precision should be chosen.
80 // To match the original float implementation, 23 bits of precision are used.
81 #define LOG_2_PRECISION_BITS 23
82 #define LOG_2_RECIPROCAL 1.44269504088896338700465094007086
83 // LOG_2_RECIPROCAL * (1 << LOG_2_PRECISION_BITS)
84 #define LOG_2_RECIPROCAL_FIXED_DOUBLE 12102203.161561485379934310913085937500
85 #define LOG_2_RECIPROCAL_FIXED ((uint64_t)12102203)
86 #define LOG_LOOKUP_IDX_MAX 256
87 extern const uint32_t kLog2Table[LOG_LOOKUP_IDX_MAX];
88 extern const uint64_t kSLog2Table[LOG_LOOKUP_IDX_MAX];
89 typedef uint32_t (*VP8LFastLog2SlowFunc)(uint32_t v);
90 typedef uint64_t (*VP8LFastSLog2SlowFunc)(uint32_t v);
91
92 extern VP8LFastLog2SlowFunc VP8LFastLog2Slow;
93 extern VP8LFastSLog2SlowFunc VP8LFastSLog2Slow;
94
VP8LFastLog2(uint32_t v)95 static WEBP_INLINE uint32_t VP8LFastLog2(uint32_t v) {
96 return (v < LOG_LOOKUP_IDX_MAX) ? kLog2Table[v] : VP8LFastLog2Slow(v);
97 }
98 // Fast calculation of v * log2(v) for integer input.
VP8LFastSLog2(uint32_t v)99 static WEBP_INLINE uint64_t VP8LFastSLog2(uint32_t v) {
100 return (v < LOG_LOOKUP_IDX_MAX) ? kSLog2Table[v] : VP8LFastSLog2Slow(v);
101 }
102
RightShiftRound(uint64_t v,uint32_t shift)103 static WEBP_INLINE uint64_t RightShiftRound(uint64_t v, uint32_t shift) {
104 return (v + (1ull << shift >> 1)) >> shift;
105 }
106
DivRound(int64_t a,int64_t b)107 static WEBP_INLINE int64_t DivRound(int64_t a, int64_t b) {
108 return ((a < 0) == (b < 0)) ? ((a + b / 2) / b) : ((a - b / 2) / b);
109 }
110
111 #define WEBP_INT64_MAX ((int64_t)((1ull << 63) - 1))
112 #define WEBP_UINT64_MAX (~0ull)
113
114 // -----------------------------------------------------------------------------
115 // PrefixEncode()
116
117 // Splitting of distance and length codes into prefixes and
118 // extra bits. The prefixes are encoded with an entropy code
119 // while the extra bits are stored just as normal bits.
VP8LPrefixEncodeBitsNoLUT(int distance,int * const code,int * const extra_bits)120 static WEBP_INLINE void VP8LPrefixEncodeBitsNoLUT(int distance, int* const code,
121 int* const extra_bits) {
122 const int highest_bit = BitsLog2Floor(--distance);
123 const int second_highest_bit = (distance >> (highest_bit - 1)) & 1;
124 *extra_bits = highest_bit - 1;
125 *code = 2 * highest_bit + second_highest_bit;
126 }
127
VP8LPrefixEncodeNoLUT(int distance,int * const code,int * const extra_bits,int * const extra_bits_value)128 static WEBP_INLINE void VP8LPrefixEncodeNoLUT(int distance, int* const code,
129 int* const extra_bits,
130 int* const extra_bits_value) {
131 const int highest_bit = BitsLog2Floor(--distance);
132 const int second_highest_bit = (distance >> (highest_bit - 1)) & 1;
133 *extra_bits = highest_bit - 1;
134 *extra_bits_value = distance & ((1 << *extra_bits) - 1);
135 *code = 2 * highest_bit + second_highest_bit;
136 }
137
138 #define PREFIX_LOOKUP_IDX_MAX 512
139 typedef struct {
140 int8_t code_;
141 int8_t extra_bits_;
142 } VP8LPrefixCode;
143
144 // These tables are derived using VP8LPrefixEncodeNoLUT.
145 extern const VP8LPrefixCode kPrefixEncodeCode[PREFIX_LOOKUP_IDX_MAX];
146 extern const uint8_t kPrefixEncodeExtraBitsValue[PREFIX_LOOKUP_IDX_MAX];
VP8LPrefixEncodeBits(int distance,int * const code,int * const extra_bits)147 static WEBP_INLINE void VP8LPrefixEncodeBits(int distance, int* const code,
148 int* const extra_bits) {
149 if (distance < PREFIX_LOOKUP_IDX_MAX) {
150 const VP8LPrefixCode prefix_code = kPrefixEncodeCode[distance];
151 *code = prefix_code.code_;
152 *extra_bits = prefix_code.extra_bits_;
153 } else {
154 VP8LPrefixEncodeBitsNoLUT(distance, code, extra_bits);
155 }
156 }
157
VP8LPrefixEncode(int distance,int * const code,int * const extra_bits,int * const extra_bits_value)158 static WEBP_INLINE void VP8LPrefixEncode(int distance, int* const code,
159 int* const extra_bits,
160 int* const extra_bits_value) {
161 if (distance < PREFIX_LOOKUP_IDX_MAX) {
162 const VP8LPrefixCode prefix_code = kPrefixEncodeCode[distance];
163 *code = prefix_code.code_;
164 *extra_bits = prefix_code.extra_bits_;
165 *extra_bits_value = kPrefixEncodeExtraBitsValue[distance];
166 } else {
167 VP8LPrefixEncodeNoLUT(distance, code, extra_bits, extra_bits_value);
168 }
169 }
170
171 // Sum of each component, mod 256.
172 static WEBP_UBSAN_IGNORE_UNSIGNED_OVERFLOW WEBP_INLINE
VP8LAddPixels(uint32_t a,uint32_t b)173 uint32_t VP8LAddPixels(uint32_t a, uint32_t b) {
174 const uint32_t alpha_and_green = (a & 0xff00ff00u) + (b & 0xff00ff00u);
175 const uint32_t red_and_blue = (a & 0x00ff00ffu) + (b & 0x00ff00ffu);
176 return (alpha_and_green & 0xff00ff00u) | (red_and_blue & 0x00ff00ffu);
177 }
178
179 // Difference of each component, mod 256.
180 static WEBP_UBSAN_IGNORE_UNSIGNED_OVERFLOW WEBP_INLINE
VP8LSubPixels(uint32_t a,uint32_t b)181 uint32_t VP8LSubPixels(uint32_t a, uint32_t b) {
182 const uint32_t alpha_and_green =
183 0x00ff00ffu + (a & 0xff00ff00u) - (b & 0xff00ff00u);
184 const uint32_t red_and_blue =
185 0xff00ff00u + (a & 0x00ff00ffu) - (b & 0x00ff00ffu);
186 return (alpha_and_green & 0xff00ff00u) | (red_and_blue & 0x00ff00ffu);
187 }
188
189 //------------------------------------------------------------------------------
190 // Transform-related functions used in both encoding and decoding.
191
192 // Macros used to create a batch predictor that iteratively uses a
193 // one-pixel predictor.
194
195 // The predictor is added to the output pixel (which
196 // is therefore considered as a residual) to get the final prediction.
197 #define GENERATE_PREDICTOR_ADD(PREDICTOR, PREDICTOR_ADD) \
198 static void PREDICTOR_ADD(const uint32_t* in, const uint32_t* upper, \
199 int num_pixels, uint32_t* WEBP_RESTRICT out) { \
200 int x; \
201 assert(upper != NULL); \
202 for (x = 0; x < num_pixels; ++x) { \
203 const uint32_t pred = (PREDICTOR)(&out[x - 1], upper + x); \
204 out[x] = VP8LAddPixels(in[x], pred); \
205 } \
206 }
207
208 #ifdef __cplusplus
209 } // extern "C"
210 #endif
211
212 #endif // WEBP_DSP_LOSSLESS_COMMON_H_
213