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: http://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 "./dsp.h"
39#include "../dec/vp8_dec.h"
40
41#if defined(WEBP_EXPERIMENTAL_FEATURES)
42// Do NOT activate this feature for real compression. This is only experimental!
43// This flag is for comparison purpose against JPEG's "YUVj" natural colorspace.
44// This colorspace is close to Rec.601's Y'CbCr model with the notable
45// difference of allowing larger range for luma/chroma.
46// See http://en.wikipedia.org/wiki/YCbCr#JPEG_conversion paragraph, and its
47// difference with http://en.wikipedia.org/wiki/YCbCr#ITU-R_BT.601_conversion
48// #define USE_YUVj
49#endif
50
51//------------------------------------------------------------------------------
52// YUV -> RGB conversion
53
54#ifdef __cplusplus
55extern "C" {
56#endif
57
58enum {
59 YUV_FIX = 16, // fixed-point precision for RGB->YUV
60 YUV_HALF = 1 << (YUV_FIX - 1),
61 YUV_MASK = (256 << YUV_FIX) - 1,
62 YUV_RANGE_MIN = -227, // min value of r/g/b output
63 YUV_RANGE_MAX = 256 + 226, // max value of r/g/b output
64
65 YUV_FIX2 = 6, // fixed-point precision for YUV->RGB
66 YUV_HALF2 = 1 << YUV_FIX2 >> 1,
67 YUV_MASK2 = (256 << YUV_FIX2) - 1
68};
69
70//------------------------------------------------------------------------------
71// slower on x86 by ~7-8%, but bit-exact with the SSE2/NEON version
72
73static WEBP_INLINE int MultHi(int v, int coeff) { // _mm_mulhi_epu16 emulation
74 return (v * coeff) >> 8;
75}
76
77static WEBP_INLINE int VP8Clip8(int v) {
78 return ((v & ~YUV_MASK2) == 0) ? (v >> YUV_FIX2) : (v < 0) ? 0 : 255;
79}
80
81static WEBP_INLINE int VP8YUVToR(int y, int v) {
82 return VP8Clip8(MultHi(y, 19077) + MultHi(v, 26149) - 14234);
83}
84
85static WEBP_INLINE int VP8YUVToG(int y, int u, int v) {
86 return VP8Clip8(MultHi(y, 19077) - MultHi(u, 6419) - MultHi(v, 13320) + 8708);
87}
88
89static WEBP_INLINE int VP8YUVToB(int y, int u) {
90 return VP8Clip8(MultHi(y, 19077) + MultHi(u, 33050) - 17685);
91}
92
93static WEBP_INLINE void VP8YuvToRgb(int y, int u, int v,
94 uint8_t* const rgb) {
95 rgb[0] = VP8YUVToR(y, v);
96 rgb[1] = VP8YUVToG(y, u, v);
97 rgb[2] = VP8YUVToB(y, u);
98}
99
100static WEBP_INLINE void VP8YuvToBgr(int y, int u, int v,
101 uint8_t* const bgr) {
102 bgr[0] = VP8YUVToB(y, u);
103 bgr[1] = VP8YUVToG(y, u, v);
104 bgr[2] = VP8YUVToR(y, v);
105}
106
107static WEBP_INLINE void VP8YuvToRgb565(int y, int u, int v,
108 uint8_t* const rgb) {
109 const int r = VP8YUVToR(y, v); // 5 usable bits
110 const int g = VP8YUVToG(y, u, v); // 6 usable bits
111 const int b = VP8YUVToB(y, u); // 5 usable bits
112 const int rg = (r & 0xf8) | (g >> 5);
113 const int gb = ((g << 3) & 0xe0) | (b >> 3);
114#ifdef WEBP_SWAP_16BIT_CSP
115 rgb[0] = gb;
116 rgb[1] = rg;
117#else
118 rgb[0] = rg;
119 rgb[1] = gb;
120#endif
121}
122
123static WEBP_INLINE void VP8YuvToRgba4444(int y, int u, int v,
124 uint8_t* const argb) {
125 const int r = VP8YUVToR(y, v); // 4 usable bits
126 const int g = VP8YUVToG(y, u, v); // 4 usable bits
127 const int b = VP8YUVToB(y, u); // 4 usable bits
128 const int rg = (r & 0xf0) | (g >> 4);
129 const int ba = (b & 0xf0) | 0x0f; // overwrite the lower 4 bits
130#ifdef WEBP_SWAP_16BIT_CSP
131 argb[0] = ba;
132 argb[1] = rg;
133#else
134 argb[0] = rg;
135 argb[1] = ba;
136#endif
137}
138
139//-----------------------------------------------------------------------------
140// Alpha handling variants
141
142static WEBP_INLINE void VP8YuvToArgb(uint8_t y, uint8_t u, uint8_t v,
143 uint8_t* const argb) {
144 argb[0] = 0xff;
145 VP8YuvToRgb(y, u, v, argb + 1);
146}
147
148static WEBP_INLINE void VP8YuvToBgra(uint8_t y, uint8_t u, uint8_t v,
149 uint8_t* const bgra) {
150 VP8YuvToBgr(y, u, v, bgra);
151 bgra[3] = 0xff;
152}
153
154static WEBP_INLINE void VP8YuvToRgba(uint8_t y, uint8_t u, uint8_t v,
155 uint8_t* const rgba) {
156 VP8YuvToRgb(y, u, v, rgba);
157 rgba[3] = 0xff;
158}
159
160// Must be called before everything, to initialize the tables.
161void VP8YUVInit(void);
162
163//-----------------------------------------------------------------------------
164// SSE2 extra functions (mostly for upsampling_sse2.c)
165
166#if defined(WEBP_USE_SSE2)
167
168// Process 32 pixels and store the result (16b, 24b or 32b per pixel) in *dst.
169void VP8YuvToRgba32(const uint8_t* y, const uint8_t* u, const uint8_t* v,
170 uint8_t* dst);
171void VP8YuvToRgb32(const uint8_t* y, const uint8_t* u, const uint8_t* v,
172 uint8_t* dst);
173void VP8YuvToBgra32(const uint8_t* y, const uint8_t* u, const uint8_t* v,
174 uint8_t* dst);
175void VP8YuvToBgr32(const uint8_t* y, const uint8_t* u, const uint8_t* v,
176 uint8_t* dst);
177void VP8YuvToArgb32(const uint8_t* y, const uint8_t* u, const uint8_t* v,
178 uint8_t* dst);
179void VP8YuvToRgba444432(const uint8_t* y, const uint8_t* u, const uint8_t* v,
180 uint8_t* dst);
181void VP8YuvToRgb56532(const uint8_t* y, const uint8_t* u, const uint8_t* v,
182 uint8_t* dst);
183
184#endif // WEBP_USE_SSE2
185
186//------------------------------------------------------------------------------
187// RGB -> YUV conversion
188
189// Stub functions that can be called with various rounding values:
190static WEBP_INLINE int VP8ClipUV(int uv, int rounding) {
191 uv = (uv + rounding + (128 << (YUV_FIX + 2))) >> (YUV_FIX + 2);
192 return ((uv & ~0xff) == 0) ? uv : (uv < 0) ? 0 : 255;
193}
194
195#ifndef USE_YUVj
196
197static WEBP_INLINE int VP8RGBToY(int r, int g, int b, int rounding) {
198 const int luma = 16839 * r + 33059 * g + 6420 * b;
199 return (luma + rounding + (16 << YUV_FIX)) >> YUV_FIX; // no need to clip
200}
201
202static WEBP_INLINE int VP8RGBToU(int r, int g, int b, int rounding) {
203 const int u = -9719 * r - 19081 * g + 28800 * b;
204 return VP8ClipUV(u, rounding);
205}
206
207static WEBP_INLINE int VP8RGBToV(int r, int g, int b, int rounding) {
208 const int v = +28800 * r - 24116 * g - 4684 * b;
209 return VP8ClipUV(v, rounding);
210}
211
212#else
213
214// This JPEG-YUV colorspace, only for comparison!
215// These are also 16bit precision coefficients from Rec.601, but with full
216// [0..255] output range.
217static WEBP_INLINE int VP8RGBToY(int r, int g, int b, int rounding) {
218 const int luma = 19595 * r + 38470 * g + 7471 * b;
219 return (luma + rounding) >> YUV_FIX; // no need to clip
220}
221
222static WEBP_INLINE int VP8RGBToU(int r, int g, int b, int rounding) {
223 const int u = -11058 * r - 21710 * g + 32768 * b;
224 return VP8ClipUV(u, rounding);
225}
226
227static WEBP_INLINE int VP8RGBToV(int r, int g, int b, int rounding) {
228 const int v = 32768 * r - 27439 * g - 5329 * b;
229 return VP8ClipUV(v, rounding);
230}
231
232#endif // USE_YUVj
233
234#ifdef __cplusplus
235} // extern "C"
236#endif
237
238#endif /* WEBP_DSP_YUV_H_ */
239