1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
|
// Copyright 2012 Google Inc. All Rights Reserved.
//
// Use of this source code is governed by a BSD-style license
// that can be found in the COPYING file in the root of the source
// tree. An additional intellectual property rights grant can be found
// in the file PATENTS. All contributing project authors may
// be found in the AUTHORS file in the root of the source tree.
// -----------------------------------------------------------------------------
//
// Image transforms and color space conversion methods for lossless decoder.
//
// Authors: Vikas Arora (vikaas.arora@gmail.com)
// Jyrki Alakuijala (jyrki@google.com)
// Vincent Rabaud (vrabaud@google.com)
#ifndef WEBP_DSP_LOSSLESS_COMMON_H_
#define WEBP_DSP_LOSSLESS_COMMON_H_
#include "src/webp/types.h"
#include "src/utils/utils.h"
#ifdef __cplusplus
extern "C" {
#endif
//------------------------------------------------------------------------------
// Decoding
// color mapping related functions.
static WEBP_INLINE uint32_t VP8GetARGBIndex(uint32_t idx) {
return (idx >> 8) & 0xff;
}
static WEBP_INLINE uint8_t VP8GetAlphaIndex(uint8_t idx) {
return idx;
}
static WEBP_INLINE uint32_t VP8GetARGBValue(uint32_t val) {
return val;
}
static WEBP_INLINE uint8_t VP8GetAlphaValue(uint32_t val) {
return (val >> 8) & 0xff;
}
//------------------------------------------------------------------------------
// Misc methods.
// Computes sampled size of 'size' when sampling using 'sampling bits'.
static WEBP_INLINE uint32_t VP8LSubSampleSize(uint32_t size,
uint32_t sampling_bits) {
return (size + (1 << sampling_bits) - 1) >> sampling_bits;
}
// Converts near lossless quality into max number of bits shaved off.
static WEBP_INLINE int VP8LNearLosslessBits(int near_lossless_quality) {
// 100 -> 0
// 80..99 -> 1
// 60..79 -> 2
// 40..59 -> 3
// 20..39 -> 4
// 0..19 -> 5
return 5 - near_lossless_quality / 20;
}
// -----------------------------------------------------------------------------
// Faster logarithm for integers. Small values use a look-up table.
// The threshold till approximate version of log_2 can be used.
// Practically, we can get rid of the call to log() as the two values match to
// very high degree (the ratio of these two is 0.99999x).
// Keeping a high threshold for now.
#define APPROX_LOG_WITH_CORRECTION_MAX 65536
#define APPROX_LOG_MAX 4096
#define LOG_2_RECIPROCAL 1.44269504088896338700465094007086
#define LOG_LOOKUP_IDX_MAX 256
extern const float kLog2Table[LOG_LOOKUP_IDX_MAX];
extern const float kSLog2Table[LOG_LOOKUP_IDX_MAX];
typedef float (*VP8LFastLog2SlowFunc)(uint32_t v);
extern VP8LFastLog2SlowFunc VP8LFastLog2Slow;
extern VP8LFastLog2SlowFunc VP8LFastSLog2Slow;
static WEBP_INLINE float VP8LFastLog2(uint32_t v) {
return (v < LOG_LOOKUP_IDX_MAX) ? kLog2Table[v] : VP8LFastLog2Slow(v);
}
// Fast calculation of v * log2(v) for integer input.
static WEBP_INLINE float VP8LFastSLog2(uint32_t v) {
return (v < LOG_LOOKUP_IDX_MAX) ? kSLog2Table[v] : VP8LFastSLog2Slow(v);
}
// -----------------------------------------------------------------------------
// PrefixEncode()
// Splitting of distance and length codes into prefixes and
// extra bits. The prefixes are encoded with an entropy code
// while the extra bits are stored just as normal bits.
static WEBP_INLINE void VP8LPrefixEncodeBitsNoLUT(int distance, int* const code,
int* const extra_bits) {
const int highest_bit = BitsLog2Floor(--distance);
const int second_highest_bit = (distance >> (highest_bit - 1)) & 1;
*extra_bits = highest_bit - 1;
*code = 2 * highest_bit + second_highest_bit;
}
static WEBP_INLINE void VP8LPrefixEncodeNoLUT(int distance, int* const code,
int* const extra_bits,
int* const extra_bits_value) {
const int highest_bit = BitsLog2Floor(--distance);
const int second_highest_bit = (distance >> (highest_bit - 1)) & 1;
*extra_bits = highest_bit - 1;
*extra_bits_value = distance & ((1 << *extra_bits) - 1);
*code = 2 * highest_bit + second_highest_bit;
}
#define PREFIX_LOOKUP_IDX_MAX 512
typedef struct {
int8_t code_;
int8_t extra_bits_;
} VP8LPrefixCode;
// These tables are derived using VP8LPrefixEncodeNoLUT.
extern const VP8LPrefixCode kPrefixEncodeCode[PREFIX_LOOKUP_IDX_MAX];
extern const uint8_t kPrefixEncodeExtraBitsValue[PREFIX_LOOKUP_IDX_MAX];
static WEBP_INLINE void VP8LPrefixEncodeBits(int distance, int* const code,
int* const extra_bits) {
if (distance < PREFIX_LOOKUP_IDX_MAX) {
const VP8LPrefixCode prefix_code = kPrefixEncodeCode[distance];
*code = prefix_code.code_;
*extra_bits = prefix_code.extra_bits_;
} else {
VP8LPrefixEncodeBitsNoLUT(distance, code, extra_bits);
}
}
static WEBP_INLINE void VP8LPrefixEncode(int distance, int* const code,
int* const extra_bits,
int* const extra_bits_value) {
if (distance < PREFIX_LOOKUP_IDX_MAX) {
const VP8LPrefixCode prefix_code = kPrefixEncodeCode[distance];
*code = prefix_code.code_;
*extra_bits = prefix_code.extra_bits_;
*extra_bits_value = kPrefixEncodeExtraBitsValue[distance];
} else {
VP8LPrefixEncodeNoLUT(distance, code, extra_bits, extra_bits_value);
}
}
// Sum of each component, mod 256.
static WEBP_UBSAN_IGNORE_UNSIGNED_OVERFLOW WEBP_INLINE
uint32_t VP8LAddPixels(uint32_t a, uint32_t b) {
const uint32_t alpha_and_green = (a & 0xff00ff00u) + (b & 0xff00ff00u);
const uint32_t red_and_blue = (a & 0x00ff00ffu) + (b & 0x00ff00ffu);
return (alpha_and_green & 0xff00ff00u) | (red_and_blue & 0x00ff00ffu);
}
// Difference of each component, mod 256.
static WEBP_UBSAN_IGNORE_UNSIGNED_OVERFLOW WEBP_INLINE
uint32_t VP8LSubPixels(uint32_t a, uint32_t b) {
const uint32_t alpha_and_green =
0x00ff00ffu + (a & 0xff00ff00u) - (b & 0xff00ff00u);
const uint32_t red_and_blue =
0xff00ff00u + (a & 0x00ff00ffu) - (b & 0x00ff00ffu);
return (alpha_and_green & 0xff00ff00u) | (red_and_blue & 0x00ff00ffu);
}
//------------------------------------------------------------------------------
// Transform-related functions use din both encoding and decoding.
// Macros used to create a batch predictor that iteratively uses a
// one-pixel predictor.
// The predictor is added to the output pixel (which
// is therefore considered as a residual) to get the final prediction.
#define GENERATE_PREDICTOR_ADD(PREDICTOR, PREDICTOR_ADD) \
static void PREDICTOR_ADD(const uint32_t* in, const uint32_t* upper, \
int num_pixels, uint32_t* out) { \
int x; \
assert(upper != NULL); \
for (x = 0; x < num_pixels; ++x) { \
const uint32_t pred = (PREDICTOR)(out[x - 1], upper + x); \
out[x] = VP8LAddPixels(in[x], pred); \
} \
}
// It subtracts the prediction from the input pixel and stores the residual
// in the output pixel.
#define GENERATE_PREDICTOR_SUB(PREDICTOR, PREDICTOR_SUB) \
static void PREDICTOR_SUB(const uint32_t* in, const uint32_t* upper, \
int num_pixels, uint32_t* out) { \
int x; \
assert(upper != NULL); \
for (x = 0; x < num_pixels; ++x) { \
const uint32_t pred = (PREDICTOR)(in[x - 1], upper + x); \
out[x] = VP8LSubPixels(in[x], pred); \
} \
}
#ifdef __cplusplus
} // extern "C"
#endif
#endif // WEBP_DSP_LOSSLESS_COMMON_H_
|
