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 |
24 | extern "C" { |
25 | #endif |
26 | |
27 | //------------------------------------------------------------------------------ |
28 | // Decoding |
29 | |
30 | // color mapping related functions. |
31 | static WEBP_INLINE uint32_t VP8GetARGBIndex(uint32_t idx) { |
32 | return (idx >> 8) & 0xff; |
33 | } |
34 | |
35 | static WEBP_INLINE uint8_t VP8GetAlphaIndex(uint8_t idx) { |
36 | return idx; |
37 | } |
38 | |
39 | static WEBP_INLINE uint32_t VP8GetARGBValue(uint32_t val) { |
40 | return val; |
41 | } |
42 | |
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'. |
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. |
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 | #define LOG_2_RECIPROCAL 1.44269504088896338700465094007086 |
77 | #define LOG_LOOKUP_IDX_MAX 256 |
78 | extern const float kLog2Table[LOG_LOOKUP_IDX_MAX]; |
79 | extern const float kSLog2Table[LOG_LOOKUP_IDX_MAX]; |
80 | typedef float (*VP8LFastLog2SlowFunc)(uint32_t v); |
81 | |
82 | extern VP8LFastLog2SlowFunc VP8LFastLog2Slow; |
83 | extern VP8LFastLog2SlowFunc VP8LFastSLog2Slow; |
84 | |
85 | static 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. |
89 | static 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. |
99 | static WEBP_INLINE void VP8LPrefixEncodeBitsNoLUT(int distance, int* const code, |
100 | int* const ) { |
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 | |
107 | static WEBP_INLINE void VP8LPrefixEncodeNoLUT(int distance, int* const code, |
108 | int* const , |
109 | int* const ) { |
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 |
118 | typedef struct { |
119 | int8_t code_; |
120 | int8_t ; |
121 | } VP8LPrefixCode; |
122 | |
123 | // These tables are derived using VP8LPrefixEncodeNoLUT. |
124 | extern const VP8LPrefixCode kPrefixEncodeCode[PREFIX_LOOKUP_IDX_MAX]; |
125 | extern const uint8_t [PREFIX_LOOKUP_IDX_MAX]; |
126 | static WEBP_INLINE void VP8LPrefixEncodeBits(int distance, int* const code, |
127 | int* const ) { |
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 | |
137 | static WEBP_INLINE void VP8LPrefixEncode(int distance, int* const code, |
138 | int* const , |
139 | int* const ) { |
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. |
151 | static WEBP_UBSAN_IGNORE_UNSIGNED_OVERFLOW WEBP_INLINE |
152 | uint32_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. |
159 | static WEBP_UBSAN_IGNORE_UNSIGNED_OVERFLOW WEBP_INLINE |
160 | uint32_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) \ |
177 | static void PREDICTOR_ADD(const uint32_t* in, const uint32_t* upper, \ |
178 | int num_pixels, uint32_t* out) { \ |
179 | int x; \ |
180 | assert(upper != NULL); \ |
181 | for (x = 0; x < num_pixels; ++x) { \ |
182 | const uint32_t pred = (PREDICTOR)(out[x - 1], upper + x); \ |
183 | out[x] = VP8LAddPixels(in[x], pred); \ |
184 | } \ |
185 | } |
186 | |
187 | // It subtracts the prediction from the input pixel and stores the residual |
188 | // in the output pixel. |
189 | #define GENERATE_PREDICTOR_SUB(PREDICTOR, PREDICTOR_SUB) \ |
190 | static void PREDICTOR_SUB(const uint32_t* in, const uint32_t* upper, \ |
191 | int num_pixels, uint32_t* out) { \ |
192 | int x; \ |
193 | assert(upper != NULL); \ |
194 | for (x = 0; x < num_pixels; ++x) { \ |
195 | const uint32_t pred = (PREDICTOR)(in[x - 1], upper + x); \ |
196 | out[x] = VP8LSubPixels(in[x], pred); \ |
197 | } \ |
198 | } |
199 | |
200 | #ifdef __cplusplus |
201 | } // extern "C" |
202 | #endif |
203 | |
204 | #endif // WEBP_DSP_LOSSLESS_COMMON_H_ |
205 | |