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.
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 // In the table-lookup version (WEBP_YUV_USE_TABLE), the common factor
25 // "1.164 * (Y-16)" can be handled as an offset in the VP8kClip[] table.
26 // So in this case the formulae should be read as:
27 // R = 1.164 * [Y + 1.371 * (V-128) ] - 18.624
28 // G = 1.164 * [Y - 0.698 * (V-128) - 0.336 * (U-128)] - 18.624
29 // B = 1.164 * [Y + 1.733 * (U-128)] - 18.624
30 // once factorized. Here too, 16bit fixed precision is used.
31 //
32 // Author: Skal (pascal.massimino@gmail.com)
33
34 #ifndef WEBP_DSP_YUV_H_
35 #define WEBP_DSP_YUV_H_
36
37 #include "../dec/decode_vp8.h"
38
39 // Define the following to use the LUT-based code:
40 #define WEBP_YUV_USE_TABLE
41
42 #if defined(WEBP_EXPERIMENTAL_FEATURES)
43 // Do NOT activate this feature for real compression. This is only experimental!
44 // This flag is for comparison purpose against JPEG's "YUVj" natural colorspace.
45 // This colorspace is close to Rec.601's Y'CbCr model with the notable
46 // difference of allowing larger range for luma/chroma.
47 // See http://en.wikipedia.org/wiki/YCbCr#JPEG_conversion paragraph, and its
48 // difference with http://en.wikipedia.org/wiki/YCbCr#ITU-R_BT.601_conversion
49 // #define USE_YUVj
50 #endif
51
52 //------------------------------------------------------------------------------
53 // YUV -> RGB conversion
54
55 #if defined(__cplusplus) || defined(c_plusplus)
56 extern "C" {
57 #endif
58
59 enum { YUV_FIX = 16, // fixed-point precision
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
66 #ifdef WEBP_YUV_USE_TABLE
67
68 extern int16_t VP8kVToR[256], VP8kUToB[256];
69 extern int32_t VP8kVToG[256], VP8kUToG[256];
70 extern uint8_t VP8kClip[YUV_RANGE_MAX - YUV_RANGE_MIN];
71 extern uint8_t VP8kClip4Bits[YUV_RANGE_MAX - YUV_RANGE_MIN];
72
VP8YuvToRgb(uint8_t y,uint8_t u,uint8_t v,uint8_t * const rgb)73 static WEBP_INLINE void VP8YuvToRgb(uint8_t y, uint8_t u, uint8_t v,
74 uint8_t* const rgb) {
75 const int r_off = VP8kVToR[v];
76 const int g_off = (VP8kVToG[v] + VP8kUToG[u]) >> YUV_FIX;
77 const int b_off = VP8kUToB[u];
78 rgb[0] = VP8kClip[y + r_off - YUV_RANGE_MIN];
79 rgb[1] = VP8kClip[y + g_off - YUV_RANGE_MIN];
80 rgb[2] = VP8kClip[y + b_off - YUV_RANGE_MIN];
81 }
82
VP8YuvToBgr(uint8_t y,uint8_t u,uint8_t v,uint8_t * const bgr)83 static WEBP_INLINE void VP8YuvToBgr(uint8_t y, uint8_t u, uint8_t v,
84 uint8_t* const bgr) {
85 const int r_off = VP8kVToR[v];
86 const int g_off = (VP8kVToG[v] + VP8kUToG[u]) >> YUV_FIX;
87 const int b_off = VP8kUToB[u];
88 bgr[0] = VP8kClip[y + b_off - YUV_RANGE_MIN];
89 bgr[1] = VP8kClip[y + g_off - YUV_RANGE_MIN];
90 bgr[2] = VP8kClip[y + r_off - YUV_RANGE_MIN];
91 }
92
VP8YuvToRgb565(uint8_t y,uint8_t u,uint8_t v,uint8_t * const rgb)93 static WEBP_INLINE void VP8YuvToRgb565(uint8_t y, uint8_t u, uint8_t v,
94 uint8_t* const rgb) {
95 const int r_off = VP8kVToR[v];
96 const int g_off = (VP8kVToG[v] + VP8kUToG[u]) >> YUV_FIX;
97 const int b_off = VP8kUToB[u];
98 const uint8_t rg = ((VP8kClip[y + r_off - YUV_RANGE_MIN] & 0xf8) |
99 (VP8kClip[y + g_off - YUV_RANGE_MIN] >> 5));
100 const uint8_t gb = (((VP8kClip[y + g_off - YUV_RANGE_MIN] << 3) & 0xe0) |
101 (VP8kClip[y + b_off - YUV_RANGE_MIN] >> 3));
102 #ifdef WEBP_SWAP_16BIT_CSP
103 rgb[0] = gb;
104 rgb[1] = rg;
105 #else
106 rgb[0] = rg;
107 rgb[1] = gb;
108 #endif
109 }
110
VP8YuvToRgba4444(uint8_t y,uint8_t u,uint8_t v,uint8_t * const argb)111 static WEBP_INLINE void VP8YuvToRgba4444(uint8_t y, uint8_t u, uint8_t v,
112 uint8_t* const argb) {
113 const int r_off = VP8kVToR[v];
114 const int g_off = (VP8kVToG[v] + VP8kUToG[u]) >> YUV_FIX;
115 const int b_off = VP8kUToB[u];
116 const uint8_t rg = ((VP8kClip4Bits[y + r_off - YUV_RANGE_MIN] << 4) |
117 VP8kClip4Bits[y + g_off - YUV_RANGE_MIN]);
118 const uint8_t ba = (VP8kClip4Bits[y + b_off - YUV_RANGE_MIN] << 4) | 0x0f;
119 #ifdef WEBP_SWAP_16BIT_CSP
120 argb[0] = ba;
121 argb[1] = rg;
122 #else
123 argb[0] = rg;
124 argb[1] = ba;
125 #endif
126 }
127
128 #else // Table-free version (slower on x86)
129
130 // These constants are 16b fixed-point version of ITU-R BT.601 constants
131 #define kYScale 76309 // 1.164 = 255 / 219
132 #define kVToR 104597 // 1.596 = 255 / 112 * 0.701
133 #define kUToG 25674 // 0.391 = 255 / 112 * 0.886 * 0.114 / 0.587
134 #define kVToG 53278 // 0.813 = 255 / 112 * 0.701 * 0.299 / 0.587
135 #define kUToB 132201 // 2.018 = 255 / 112 * 0.886
136 #define kRCst (-kYScale * 16 - kVToR * 128 + YUV_HALF)
137 #define kGCst (-kYScale * 16 + kUToG * 128 + kVToG * 128 + YUV_HALF)
138 #define kBCst (-kYScale * 16 - kUToB * 128 + YUV_HALF)
139
VP8Clip8(int v)140 static WEBP_INLINE uint8_t VP8Clip8(int v) {
141 return ((v & ~YUV_MASK) == 0) ? (uint8_t)(v >> YUV_FIX)
142 : (v < 0) ? 0u : 255u;
143 }
144
VP8ClipN(int v,int N)145 static WEBP_INLINE uint8_t VP8ClipN(int v, int N) { // clip to N bits
146 return ((v & ~YUV_MASK) == 0) ? (uint8_t)(v >> (YUV_FIX + (8 - N)))
147 : (v < 0) ? 0u : (255u >> (8 - N));
148 }
149
VP8YUVToR(int y,int v)150 static WEBP_INLINE int VP8YUVToR(int y, int v) {
151 return kYScale * y + kVToR * v + kRCst;
152 }
153
VP8YUVToG(int y,int u,int v)154 static WEBP_INLINE int VP8YUVToG(int y, int u, int v) {
155 return kYScale * y - kUToG * u - kVToG * v + kGCst;
156 }
157
VP8YUVToB(int y,int u)158 static WEBP_INLINE int VP8YUVToB(int y, int u) {
159 return kYScale * y + kUToB * u + kBCst;
160 }
161
VP8YuvToRgb(uint8_t y,uint8_t u,uint8_t v,uint8_t * const rgb)162 static WEBP_INLINE void VP8YuvToRgb(uint8_t y, uint8_t u, uint8_t v,
163 uint8_t* const rgb) {
164 rgb[0] = VP8Clip8(VP8YUVToR(y, v));
165 rgb[1] = VP8Clip8(VP8YUVToG(y, u, v));
166 rgb[2] = VP8Clip8(VP8YUVToB(y, u));
167 }
168
VP8YuvToBgr(uint8_t y,uint8_t u,uint8_t v,uint8_t * const bgr)169 static WEBP_INLINE void VP8YuvToBgr(uint8_t y, uint8_t u, uint8_t v,
170 uint8_t* const bgr) {
171 bgr[0] = VP8Clip8(VP8YUVToB(y, u));
172 bgr[1] = VP8Clip8(VP8YUVToG(y, u, v));
173 bgr[2] = VP8Clip8(VP8YUVToR(y, v));
174 }
175
VP8YuvToRgb565(uint8_t y,uint8_t u,uint8_t v,uint8_t * const rgb)176 static WEBP_INLINE void VP8YuvToRgb565(uint8_t y, uint8_t u, uint8_t v,
177 uint8_t* const rgb) {
178 const int r = VP8Clip8(VP8YUVToR(y, u));
179 const int g = VP8ClipN(VP8YUVToG(y, u, v), 6);
180 const int b = VP8ClipN(VP8YUVToB(y, v), 5);
181 const uint8_t rg = (r & 0xf8) | (g >> 3);
182 const uint8_t gb = (g << 5) | b;
183 #ifdef WEBP_SWAP_16BIT_CSP
184 rgb[0] = gb;
185 rgb[1] = rg;
186 #else
187 rgb[0] = rg;
188 rgb[1] = gb;
189 #endif
190 }
191
VP8YuvToRgba4444(uint8_t y,uint8_t u,uint8_t v,uint8_t * const argb)192 static WEBP_INLINE void VP8YuvToRgba4444(uint8_t y, uint8_t u, uint8_t v,
193 uint8_t* const argb) {
194 const int r = VP8Clip8(VP8YUVToR(y, u));
195 const int g = VP8ClipN(VP8YUVToG(y, u, v), 4);
196 const int b = VP8Clip8(VP8YUVToB(y, v));
197 const uint8_t rg = (r & 0xf0) | g;
198 const uint8_t ba = b | 0x0f; // overwrite the lower 4 bits
199 #ifdef WEBP_SWAP_16BIT_CSP
200 argb[0] = ba;
201 argb[1] = rg;
202 #else
203 argb[0] = rg;
204 argb[1] = ba;
205 #endif
206 }
207
208 #endif // WEBP_YUV_USE_TABLE
209
VP8YuvToArgb(uint8_t y,uint8_t u,uint8_t v,uint8_t * const argb)210 static WEBP_INLINE void VP8YuvToArgb(uint8_t y, uint8_t u, uint8_t v,
211 uint8_t* const argb) {
212 argb[0] = 0xff;
213 VP8YuvToRgb(y, u, v, argb + 1);
214 }
215
VP8YuvToBgra(uint8_t y,uint8_t u,uint8_t v,uint8_t * const bgra)216 static WEBP_INLINE void VP8YuvToBgra(uint8_t y, uint8_t u, uint8_t v,
217 uint8_t* const bgra) {
218 VP8YuvToBgr(y, u, v, bgra);
219 bgra[3] = 0xff;
220 }
221
VP8YuvToRgba(uint8_t y,uint8_t u,uint8_t v,uint8_t * const rgba)222 static WEBP_INLINE void VP8YuvToRgba(uint8_t y, uint8_t u, uint8_t v,
223 uint8_t* const rgba) {
224 VP8YuvToRgb(y, u, v, rgba);
225 rgba[3] = 0xff;
226 }
227
228 // Must be called before everything, to initialize the tables.
229 void VP8YUVInit(void);
230
231 //------------------------------------------------------------------------------
232 // RGB -> YUV conversion
233
VP8ClipUV(int v)234 static WEBP_INLINE int VP8ClipUV(int v) {
235 v = (v + (257 << (YUV_FIX + 2 - 1))) >> (YUV_FIX + 2);
236 return ((v & ~0xff) == 0) ? v : (v < 0) ? 0 : 255;
237 }
238
239 #ifndef USE_YUVj
240
VP8RGBToY(int r,int g,int b)241 static WEBP_INLINE int VP8RGBToY(int r, int g, int b) {
242 const int kRound = (1 << (YUV_FIX - 1)) + (16 << YUV_FIX);
243 const int luma = 16839 * r + 33059 * g + 6420 * b;
244 return (luma + kRound) >> YUV_FIX; // no need to clip
245 }
246
VP8RGBToU(int r,int g,int b)247 static WEBP_INLINE int VP8RGBToU(int r, int g, int b) {
248 const int u = -9719 * r - 19081 * g + 28800 * b;
249 return VP8ClipUV(u);
250 }
251
VP8RGBToV(int r,int g,int b)252 static WEBP_INLINE int VP8RGBToV(int r, int g, int b) {
253 const int v = +28800 * r - 24116 * g - 4684 * b;
254 return VP8ClipUV(v);
255 }
256
257 #else
258
259 // This JPEG-YUV colorspace, only for comparison!
260 // These are also 16-bit precision coefficients from Rec.601, but with full
261 // [0..255] output range.
VP8RGBToY(int r,int g,int b)262 static WEBP_INLINE int VP8RGBToY(int r, int g, int b) {
263 const int kRound = (1 << (YUV_FIX - 1));
264 const int luma = 19595 * r + 38470 * g + 7471 * b;
265 return (luma + kRound) >> YUV_FIX; // no need to clip
266 }
267
VP8RGBToU(int r,int g,int b)268 static WEBP_INLINE int VP8RGBToU(int r, int g, int b) {
269 const int u = -11058 * r - 21710 * g + 32768 * b;
270 return VP8ClipUV(u);
271 }
272
VP8RGBToV(int r,int g,int b)273 static WEBP_INLINE int VP8RGBToV(int r, int g, int b) {
274 const int v = 32768 * r - 27439 * g - 5329 * b;
275 return VP8ClipUV(v);
276 }
277
278 #endif // USE_YUVj
279
280 #if defined(__cplusplus) || defined(c_plusplus)
281 } // extern "C"
282 #endif
283
284 #endif /* WEBP_DSP_YUV_H_ */
285