1// Copyright 2010 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// inline YUV<->RGB conversion function
11//
12// The exact naming is Y'CbCr, following the ITU-R BT.601 standard.
13// More information at: https://en.wikipedia.org/wiki/YCbCr
14// Y = 0.2569 * R + 0.5044 * G + 0.0979 * B + 16
15// U = -0.1483 * R - 0.2911 * G + 0.4394 * B + 128
16// V = 0.4394 * R - 0.3679 * G - 0.0715 * B + 128
17// We use 16bit fixed point operations for RGB->YUV conversion (YUV_FIX).
18//
19// For the Y'CbCr to RGB conversion, the BT.601 specification reads:
20// R = 1.164 * (Y-16) + 1.596 * (V-128)
21// G = 1.164 * (Y-16) - 0.813 * (V-128) - 0.391 * (U-128)
22// B = 1.164 * (Y-16) + 2.018 * (U-128)
23// where Y is in the [16,235] range, and U/V in the [16,240] range.
24//
25// The fixed-point implementation used here is:
26// R = (19077 . y + 26149 . v - 14234) >> 6
27// G = (19077 . y - 6419 . u - 13320 . v + 8708) >> 6
28// B = (19077 . y + 33050 . u - 17685) >> 6
29// where the '.' operator is the mulhi_epu16 variant:
30// a . b = ((a << 8) * b) >> 16
31// that preserves 8 bits of fractional precision before final descaling.
32
33// Author: Skal (pascal.massimino@gmail.com)
34
35#ifndef WEBP_DSP_YUV_H_
36#define WEBP_DSP_YUV_H_
37
38#include "src/dsp/dsp.h"
39#include "src/dec/vp8_dec.h"
40
41//------------------------------------------------------------------------------
42// YUV -> RGB conversion
43
44#ifdef __cplusplus
45extern "C" {
46#endif
47
48enum {
49 YUV_FIX = 16, // fixed-point precision for RGB->YUV
50 YUV_HALF = 1 << (YUV_FIX - 1),
51
52 YUV_FIX2 = 6, // fixed-point precision for YUV->RGB
53 YUV_MASK2 = (256 << YUV_FIX2) - 1
54};
55
56//------------------------------------------------------------------------------
57// slower on x86 by ~7-8%, but bit-exact with the SSE2/NEON version
58
59static WEBP_INLINE int MultHi(int v, int coeff) { // _mm_mulhi_epu16 emulation
60 return (v * coeff) >> 8;
61}
62
63static WEBP_INLINE int VP8Clip8(int v) {
64 return ((v & ~YUV_MASK2) == 0) ? (v >> YUV_FIX2) : (v < 0) ? 0 : 255;
65}
66
67static WEBP_INLINE int VP8YUVToR(int y, int v) {
68 return VP8Clip8(MultHi(y, 19077) + MultHi(v, 26149) - 14234);
69}
70
71static WEBP_INLINE int VP8YUVToG(int y, int u, int v) {
72 return VP8Clip8(MultHi(y, 19077) - MultHi(u, 6419) - MultHi(v, 13320) + 8708);
73}
74
75static WEBP_INLINE int VP8YUVToB(int y, int u) {
76 return VP8Clip8(MultHi(y, 19077) + MultHi(u, 33050) - 17685);
77}
78
79static WEBP_INLINE void VP8YuvToRgb(int y, int u, int v,
80 uint8_t* const rgb) {
81 rgb[0] = VP8YUVToR(y, v);
82 rgb[1] = VP8YUVToG(y, u, v);
83 rgb[2] = VP8YUVToB(y, u);
84}
85
86static WEBP_INLINE void VP8YuvToBgr(int y, int u, int v,
87 uint8_t* const bgr) {
88 bgr[0] = VP8YUVToB(y, u);
89 bgr[1] = VP8YUVToG(y, u, v);
90 bgr[2] = VP8YUVToR(y, v);
91}
92
93static WEBP_INLINE void VP8YuvToRgb565(int y, int u, int v,
94 uint8_t* const rgb) {
95 const int r = VP8YUVToR(y, v); // 5 usable bits
96 const int g = VP8YUVToG(y, u, v); // 6 usable bits
97 const int b = VP8YUVToB(y, u); // 5 usable bits
98 const int rg = (r & 0xf8) | (g >> 5);
99 const int gb = ((g << 3) & 0xe0) | (b >> 3);
100#if (WEBP_SWAP_16BIT_CSP == 1)
101 rgb[0] = gb;
102 rgb[1] = rg;
103#else
104 rgb[0] = rg;
105 rgb[1] = gb;
106#endif
107}
108
109static WEBP_INLINE void VP8YuvToRgba4444(int y, int u, int v,
110 uint8_t* const argb) {
111 const int r = VP8YUVToR(y, v); // 4 usable bits
112 const int g = VP8YUVToG(y, u, v); // 4 usable bits
113 const int b = VP8YUVToB(y, u); // 4 usable bits
114 const int rg = (r & 0xf0) | (g >> 4);
115 const int ba = (b & 0xf0) | 0x0f; // overwrite the lower 4 bits
116#if (WEBP_SWAP_16BIT_CSP == 1)
117 argb[0] = ba;
118 argb[1] = rg;
119#else
120 argb[0] = rg;
121 argb[1] = ba;
122#endif
123}
124
125//-----------------------------------------------------------------------------
126// Alpha handling variants
127
128static WEBP_INLINE void VP8YuvToArgb(uint8_t y, uint8_t u, uint8_t v,
129 uint8_t* const argb) {
130 argb[0] = 0xff;
131 VP8YuvToRgb(y, u, v, argb + 1);
132}
133
134static WEBP_INLINE void VP8YuvToBgra(uint8_t y, uint8_t u, uint8_t v,
135 uint8_t* const bgra) {
136 VP8YuvToBgr(y, u, v, bgra);
137 bgra[3] = 0xff;
138}
139
140static WEBP_INLINE void VP8YuvToRgba(uint8_t y, uint8_t u, uint8_t v,
141 uint8_t* const rgba) {
142 VP8YuvToRgb(y, u, v, rgba);
143 rgba[3] = 0xff;
144}
145
146//-----------------------------------------------------------------------------
147// SSE2 extra functions (mostly for upsampling_sse2.c)
148
149#if defined(WEBP_USE_SSE2)
150
151// Process 32 pixels and store the result (16b, 24b or 32b per pixel) in *dst.
152void VP8YuvToRgba32_SSE2(const uint8_t* y, const uint8_t* u, const uint8_t* v,
153 uint8_t* dst);
154void VP8YuvToRgb32_SSE2(const uint8_t* y, const uint8_t* u, const uint8_t* v,
155 uint8_t* dst);
156void VP8YuvToBgra32_SSE2(const uint8_t* y, const uint8_t* u, const uint8_t* v,
157 uint8_t* dst);
158void VP8YuvToBgr32_SSE2(const uint8_t* y, const uint8_t* u, const uint8_t* v,
159 uint8_t* dst);
160void VP8YuvToArgb32_SSE2(const uint8_t* y, const uint8_t* u, const uint8_t* v,
161 uint8_t* dst);
162void VP8YuvToRgba444432_SSE2(const uint8_t* y, const uint8_t* u,
163 const uint8_t* v, uint8_t* dst);
164void VP8YuvToRgb56532_SSE2(const uint8_t* y, const uint8_t* u, const uint8_t* v,
165 uint8_t* dst);
166
167#endif // WEBP_USE_SSE2
168
169//-----------------------------------------------------------------------------
170// SSE41 extra functions (mostly for upsampling_sse41.c)
171
172#if defined(WEBP_USE_SSE41)
173
174// Process 32 pixels and store the result (16b, 24b or 32b per pixel) in *dst.
175void VP8YuvToRgb32_SSE41(const uint8_t* y, const uint8_t* u, const uint8_t* v,
176 uint8_t* dst);
177void VP8YuvToBgr32_SSE41(const uint8_t* y, const uint8_t* u, const uint8_t* v,
178 uint8_t* dst);
179
180#endif // WEBP_USE_SSE41
181
182//------------------------------------------------------------------------------
183// RGB -> YUV conversion
184
185// Stub functions that can be called with various rounding values:
186static WEBP_INLINE int VP8ClipUV(int uv, int rounding) {
187 uv = (uv + rounding + (128 << (YUV_FIX + 2))) >> (YUV_FIX + 2);
188 return ((uv & ~0xff) == 0) ? uv : (uv < 0) ? 0 : 255;
189}
190
191static WEBP_INLINE int VP8RGBToY(int r, int g, int b, int rounding) {
192 const int luma = 16839 * r + 33059 * g + 6420 * b;
193 return (luma + rounding + (16 << YUV_FIX)) >> YUV_FIX; // no need to clip
194}
195
196static WEBP_INLINE int VP8RGBToU(int r, int g, int b, int rounding) {
197 const int u = -9719 * r - 19081 * g + 28800 * b;
198 return VP8ClipUV(u, rounding);
199}
200
201static WEBP_INLINE int VP8RGBToV(int r, int g, int b, int rounding) {
202 const int v = +28800 * r - 24116 * g - 4684 * b;
203 return VP8ClipUV(v, rounding);
204}
205
206#ifdef __cplusplus
207} // extern "C"
208#endif
209
210#endif // WEBP_DSP_YUV_H_
211