• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1 // Copyright 2013 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 // Utilities for processing transparent channel.
11 //
12 // Author: Skal (pascal.massimino@gmail.com)
13 
14 #include <assert.h>
15 #include "./dsp.h"
16 
17 // Tables can be faster on some platform but incur some extra binary size (~2k).
18 // #define USE_TABLES_FOR_ALPHA_MULT
19 
20 // -----------------------------------------------------------------------------
21 
22 #define MFIX 24    // 24bit fixed-point arithmetic
23 #define HALF ((1u << MFIX) >> 1)
24 #define KINV_255 ((1u << MFIX) / 255u)
25 
Mult(uint8_t x,uint32_t mult)26 static uint32_t Mult(uint8_t x, uint32_t mult) {
27   const uint32_t v = (x * mult + HALF) >> MFIX;
28   assert(v <= 255);  // <- 24bit precision is enough to ensure that.
29   return v;
30 }
31 
32 #ifdef USE_TABLES_FOR_ALPHA_MULT
33 
34 static const uint32_t kMultTables[2][256] = {
35   {    // (255u << MFIX) / alpha
36     0x00000000, 0xff000000, 0x7f800000, 0x55000000, 0x3fc00000, 0x33000000,
37     0x2a800000, 0x246db6db, 0x1fe00000, 0x1c555555, 0x19800000, 0x172e8ba2,
38     0x15400000, 0x139d89d8, 0x1236db6d, 0x11000000, 0x0ff00000, 0x0f000000,
39     0x0e2aaaaa, 0x0d6bca1a, 0x0cc00000, 0x0c249249, 0x0b9745d1, 0x0b1642c8,
40     0x0aa00000, 0x0a333333, 0x09cec4ec, 0x0971c71c, 0x091b6db6, 0x08cb08d3,
41     0x08800000, 0x0839ce73, 0x07f80000, 0x07ba2e8b, 0x07800000, 0x07492492,
42     0x07155555, 0x06e45306, 0x06b5e50d, 0x0689d89d, 0x06600000, 0x063831f3,
43     0x06124924, 0x05ee23b8, 0x05cba2e8, 0x05aaaaaa, 0x058b2164, 0x056cefa8,
44     0x05500000, 0x05343eb1, 0x05199999, 0x05000000, 0x04e76276, 0x04cfb2b7,
45     0x04b8e38e, 0x04a2e8ba, 0x048db6db, 0x0479435e, 0x04658469, 0x045270d0,
46     0x04400000, 0x042e29f7, 0x041ce739, 0x040c30c3, 0x03fc0000, 0x03ec4ec4,
47     0x03dd1745, 0x03ce540f, 0x03c00000, 0x03b21642, 0x03a49249, 0x03976fc6,
48     0x038aaaaa, 0x037e3f1f, 0x03722983, 0x03666666, 0x035af286, 0x034fcace,
49     0x0344ec4e, 0x033a5440, 0x03300000, 0x0325ed09, 0x031c18f9, 0x0312818a,
50     0x03092492, 0x03000000, 0x02f711dc, 0x02ee5846, 0x02e5d174, 0x02dd7baf,
51     0x02d55555, 0x02cd5cd5, 0x02c590b2, 0x02bdef7b, 0x02b677d4, 0x02af286b,
52     0x02a80000, 0x02a0fd5c, 0x029a1f58, 0x029364d9, 0x028ccccc, 0x0286562d,
53     0x02800000, 0x0279c952, 0x0273b13b, 0x026db6db, 0x0267d95b, 0x026217ec,
54     0x025c71c7, 0x0256e62a, 0x0251745d, 0x024c1bac, 0x0246db6d, 0x0241b2f9,
55     0x023ca1af, 0x0237a6f4, 0x0232c234, 0x022df2df, 0x02293868, 0x02249249,
56     0x02200000, 0x021b810e, 0x021714fb, 0x0212bb51, 0x020e739c, 0x020a3d70,
57     0x02061861, 0x02020408, 0x01fe0000, 0x01fa0be8, 0x01f62762, 0x01f25213,
58     0x01ee8ba2, 0x01ead3ba, 0x01e72a07, 0x01e38e38, 0x01e00000, 0x01dc7f10,
59     0x01d90b21, 0x01d5a3e9, 0x01d24924, 0x01cefa8d, 0x01cbb7e3, 0x01c880e5,
60     0x01c55555, 0x01c234f7, 0x01bf1f8f, 0x01bc14e5, 0x01b914c1, 0x01b61eed,
61     0x01b33333, 0x01b05160, 0x01ad7943, 0x01aaaaaa, 0x01a7e567, 0x01a5294a,
62     0x01a27627, 0x019fcbd2, 0x019d2a20, 0x019a90e7, 0x01980000, 0x01957741,
63     0x0192f684, 0x01907da4, 0x018e0c7c, 0x018ba2e8, 0x018940c5, 0x0186e5f0,
64     0x01849249, 0x018245ae, 0x01800000, 0x017dc11f, 0x017b88ee, 0x0179574e,
65     0x01772c23, 0x01750750, 0x0172e8ba, 0x0170d045, 0x016ebdd7, 0x016cb157,
66     0x016aaaaa, 0x0168a9b9, 0x0166ae6a, 0x0164b8a7, 0x0162c859, 0x0160dd67,
67     0x015ef7bd, 0x015d1745, 0x015b3bea, 0x01596596, 0x01579435, 0x0155c7b4,
68     0x01540000, 0x01523d03, 0x01507eae, 0x014ec4ec, 0x014d0fac, 0x014b5edc,
69     0x0149b26c, 0x01480a4a, 0x01466666, 0x0144c6af, 0x01432b16, 0x0141938b,
70     0x01400000, 0x013e7063, 0x013ce4a9, 0x013b5cc0, 0x0139d89d, 0x01385830,
71     0x0136db6d, 0x01356246, 0x0133ecad, 0x01327a97, 0x01310bf6, 0x012fa0be,
72     0x012e38e3, 0x012cd459, 0x012b7315, 0x012a150a, 0x0128ba2e, 0x01276276,
73     0x01260dd6, 0x0124bc44, 0x01236db6, 0x01222222, 0x0120d97c, 0x011f93bc,
74     0x011e50d7, 0x011d10c4, 0x011bd37a, 0x011a98ef, 0x0119611a, 0x01182bf2,
75     0x0116f96f, 0x0115c988, 0x01149c34, 0x0113716a, 0x01124924, 0x01112358,
76     0x01100000, 0x010edf12, 0x010dc087, 0x010ca458, 0x010b8a7d, 0x010a72f0,
77     0x01095da8, 0x01084a9f, 0x010739ce, 0x01062b2e, 0x01051eb8, 0x01041465,
78     0x01030c30, 0x01020612, 0x01010204, 0x01000000 },
79   {   // alpha * KINV_255
80     0x00000000, 0x00010101, 0x00020202, 0x00030303, 0x00040404, 0x00050505,
81     0x00060606, 0x00070707, 0x00080808, 0x00090909, 0x000a0a0a, 0x000b0b0b,
82     0x000c0c0c, 0x000d0d0d, 0x000e0e0e, 0x000f0f0f, 0x00101010, 0x00111111,
83     0x00121212, 0x00131313, 0x00141414, 0x00151515, 0x00161616, 0x00171717,
84     0x00181818, 0x00191919, 0x001a1a1a, 0x001b1b1b, 0x001c1c1c, 0x001d1d1d,
85     0x001e1e1e, 0x001f1f1f, 0x00202020, 0x00212121, 0x00222222, 0x00232323,
86     0x00242424, 0x00252525, 0x00262626, 0x00272727, 0x00282828, 0x00292929,
87     0x002a2a2a, 0x002b2b2b, 0x002c2c2c, 0x002d2d2d, 0x002e2e2e, 0x002f2f2f,
88     0x00303030, 0x00313131, 0x00323232, 0x00333333, 0x00343434, 0x00353535,
89     0x00363636, 0x00373737, 0x00383838, 0x00393939, 0x003a3a3a, 0x003b3b3b,
90     0x003c3c3c, 0x003d3d3d, 0x003e3e3e, 0x003f3f3f, 0x00404040, 0x00414141,
91     0x00424242, 0x00434343, 0x00444444, 0x00454545, 0x00464646, 0x00474747,
92     0x00484848, 0x00494949, 0x004a4a4a, 0x004b4b4b, 0x004c4c4c, 0x004d4d4d,
93     0x004e4e4e, 0x004f4f4f, 0x00505050, 0x00515151, 0x00525252, 0x00535353,
94     0x00545454, 0x00555555, 0x00565656, 0x00575757, 0x00585858, 0x00595959,
95     0x005a5a5a, 0x005b5b5b, 0x005c5c5c, 0x005d5d5d, 0x005e5e5e, 0x005f5f5f,
96     0x00606060, 0x00616161, 0x00626262, 0x00636363, 0x00646464, 0x00656565,
97     0x00666666, 0x00676767, 0x00686868, 0x00696969, 0x006a6a6a, 0x006b6b6b,
98     0x006c6c6c, 0x006d6d6d, 0x006e6e6e, 0x006f6f6f, 0x00707070, 0x00717171,
99     0x00727272, 0x00737373, 0x00747474, 0x00757575, 0x00767676, 0x00777777,
100     0x00787878, 0x00797979, 0x007a7a7a, 0x007b7b7b, 0x007c7c7c, 0x007d7d7d,
101     0x007e7e7e, 0x007f7f7f, 0x00808080, 0x00818181, 0x00828282, 0x00838383,
102     0x00848484, 0x00858585, 0x00868686, 0x00878787, 0x00888888, 0x00898989,
103     0x008a8a8a, 0x008b8b8b, 0x008c8c8c, 0x008d8d8d, 0x008e8e8e, 0x008f8f8f,
104     0x00909090, 0x00919191, 0x00929292, 0x00939393, 0x00949494, 0x00959595,
105     0x00969696, 0x00979797, 0x00989898, 0x00999999, 0x009a9a9a, 0x009b9b9b,
106     0x009c9c9c, 0x009d9d9d, 0x009e9e9e, 0x009f9f9f, 0x00a0a0a0, 0x00a1a1a1,
107     0x00a2a2a2, 0x00a3a3a3, 0x00a4a4a4, 0x00a5a5a5, 0x00a6a6a6, 0x00a7a7a7,
108     0x00a8a8a8, 0x00a9a9a9, 0x00aaaaaa, 0x00ababab, 0x00acacac, 0x00adadad,
109     0x00aeaeae, 0x00afafaf, 0x00b0b0b0, 0x00b1b1b1, 0x00b2b2b2, 0x00b3b3b3,
110     0x00b4b4b4, 0x00b5b5b5, 0x00b6b6b6, 0x00b7b7b7, 0x00b8b8b8, 0x00b9b9b9,
111     0x00bababa, 0x00bbbbbb, 0x00bcbcbc, 0x00bdbdbd, 0x00bebebe, 0x00bfbfbf,
112     0x00c0c0c0, 0x00c1c1c1, 0x00c2c2c2, 0x00c3c3c3, 0x00c4c4c4, 0x00c5c5c5,
113     0x00c6c6c6, 0x00c7c7c7, 0x00c8c8c8, 0x00c9c9c9, 0x00cacaca, 0x00cbcbcb,
114     0x00cccccc, 0x00cdcdcd, 0x00cecece, 0x00cfcfcf, 0x00d0d0d0, 0x00d1d1d1,
115     0x00d2d2d2, 0x00d3d3d3, 0x00d4d4d4, 0x00d5d5d5, 0x00d6d6d6, 0x00d7d7d7,
116     0x00d8d8d8, 0x00d9d9d9, 0x00dadada, 0x00dbdbdb, 0x00dcdcdc, 0x00dddddd,
117     0x00dedede, 0x00dfdfdf, 0x00e0e0e0, 0x00e1e1e1, 0x00e2e2e2, 0x00e3e3e3,
118     0x00e4e4e4, 0x00e5e5e5, 0x00e6e6e6, 0x00e7e7e7, 0x00e8e8e8, 0x00e9e9e9,
119     0x00eaeaea, 0x00ebebeb, 0x00ececec, 0x00ededed, 0x00eeeeee, 0x00efefef,
120     0x00f0f0f0, 0x00f1f1f1, 0x00f2f2f2, 0x00f3f3f3, 0x00f4f4f4, 0x00f5f5f5,
121     0x00f6f6f6, 0x00f7f7f7, 0x00f8f8f8, 0x00f9f9f9, 0x00fafafa, 0x00fbfbfb,
122     0x00fcfcfc, 0x00fdfdfd, 0x00fefefe, 0x00ffffff }
123 };
124 
GetScale(uint32_t a,int inverse)125 static WEBP_INLINE uint32_t GetScale(uint32_t a, int inverse) {
126   return kMultTables[!inverse][a];
127 }
128 
129 #else
130 
GetScale(uint32_t a,int inverse)131 static WEBP_INLINE uint32_t GetScale(uint32_t a, int inverse) {
132   return inverse ? (255u << MFIX) / a : a * KINV_255;
133 }
134 
135 #endif    // USE_TABLES_FOR_ALPHA_MULT
136 
WebPMultARGBRowC(uint32_t * const ptr,int width,int inverse)137 void WebPMultARGBRowC(uint32_t* const ptr, int width, int inverse) {
138   int x;
139   for (x = 0; x < width; ++x) {
140     const uint32_t argb = ptr[x];
141     if (argb < 0xff000000u) {      // alpha < 255
142       if (argb <= 0x00ffffffu) {   // alpha == 0
143         ptr[x] = 0;
144       } else {
145         const uint32_t alpha = (argb >> 24) & 0xff;
146         const uint32_t scale = GetScale(alpha, inverse);
147         uint32_t out = argb & 0xff000000u;
148         out |= Mult(argb >>  0, scale) <<  0;
149         out |= Mult(argb >>  8, scale) <<  8;
150         out |= Mult(argb >> 16, scale) << 16;
151         ptr[x] = out;
152       }
153     }
154   }
155 }
156 
WebPMultRowC(uint8_t * const ptr,const uint8_t * const alpha,int width,int inverse)157 void WebPMultRowC(uint8_t* const ptr, const uint8_t* const alpha,
158                   int width, int inverse) {
159   int x;
160   for (x = 0; x < width; ++x) {
161     const uint32_t a = alpha[x];
162     if (a != 255) {
163       if (a == 0) {
164         ptr[x] = 0;
165       } else {
166         const uint32_t scale = GetScale(a, inverse);
167         ptr[x] = Mult(ptr[x], scale);
168       }
169     }
170   }
171 }
172 
173 #undef KINV_255
174 #undef HALF
175 #undef MFIX
176 
177 void (*WebPMultARGBRow)(uint32_t* const ptr, int width, int inverse);
178 void (*WebPMultRow)(uint8_t* const ptr, const uint8_t* const alpha,
179                     int width, int inverse);
180 
181 //------------------------------------------------------------------------------
182 // Generic per-plane calls
183 
WebPMultARGBRows(uint8_t * ptr,int stride,int width,int num_rows,int inverse)184 void WebPMultARGBRows(uint8_t* ptr, int stride, int width, int num_rows,
185                       int inverse) {
186   int n;
187   for (n = 0; n < num_rows; ++n) {
188     WebPMultARGBRow((uint32_t*)ptr, width, inverse);
189     ptr += stride;
190   }
191 }
192 
WebPMultRows(uint8_t * ptr,int stride,const uint8_t * alpha,int alpha_stride,int width,int num_rows,int inverse)193 void WebPMultRows(uint8_t* ptr, int stride,
194                   const uint8_t* alpha, int alpha_stride,
195                   int width, int num_rows, int inverse) {
196   int n;
197   for (n = 0; n < num_rows; ++n) {
198     WebPMultRow(ptr, alpha, width, inverse);
199     ptr += stride;
200     alpha += alpha_stride;
201   }
202 }
203 
204 //------------------------------------------------------------------------------
205 // Premultiplied modes
206 
207 // non dithered-modes
208 
209 // (x * a * 32897) >> 23 is bit-wise equivalent to (int)(x * a / 255.)
210 // for all 8bit x or a. For bit-wise equivalence to (int)(x * a / 255. + .5),
211 // one can use instead: (x * a * 65793 + (1 << 23)) >> 24
212 #if 1     // (int)(x * a / 255.)
213 #define MULTIPLIER(a)   ((a) * 32897U)
214 #define PREMULTIPLY(x, m) (((x) * (m)) >> 23)
215 #else     // (int)(x * a / 255. + .5)
216 #define MULTIPLIER(a) ((a) * 65793U)
217 #define PREMULTIPLY(x, m) (((x) * (m) + (1U << 23)) >> 24)
218 #endif
219 
ApplyAlphaMultiply(uint8_t * rgba,int alpha_first,int w,int h,int stride)220 static void ApplyAlphaMultiply(uint8_t* rgba, int alpha_first,
221                                int w, int h, int stride) {
222   while (h-- > 0) {
223     uint8_t* const rgb = rgba + (alpha_first ? 1 : 0);
224     const uint8_t* const alpha = rgba + (alpha_first ? 0 : 3);
225     int i;
226     for (i = 0; i < w; ++i) {
227       const uint32_t a = alpha[4 * i];
228       if (a != 0xff) {
229         const uint32_t mult = MULTIPLIER(a);
230         rgb[4 * i + 0] = PREMULTIPLY(rgb[4 * i + 0], mult);
231         rgb[4 * i + 1] = PREMULTIPLY(rgb[4 * i + 1], mult);
232         rgb[4 * i + 2] = PREMULTIPLY(rgb[4 * i + 2], mult);
233       }
234     }
235     rgba += stride;
236   }
237 }
238 #undef MULTIPLIER
239 #undef PREMULTIPLY
240 
241 // rgbA4444
242 
243 #define MULTIPLIER(a)  ((a) * 0x1111)    // 0x1111 ~= (1 << 16) / 15
244 
dither_hi(uint8_t x)245 static WEBP_INLINE uint8_t dither_hi(uint8_t x) {
246   return (x & 0xf0) | (x >> 4);
247 }
248 
dither_lo(uint8_t x)249 static WEBP_INLINE uint8_t dither_lo(uint8_t x) {
250   return (x & 0x0f) | (x << 4);
251 }
252 
multiply(uint8_t x,uint32_t m)253 static WEBP_INLINE uint8_t multiply(uint8_t x, uint32_t m) {
254   return (x * m) >> 16;
255 }
256 
ApplyAlphaMultiply4444(uint8_t * rgba4444,int w,int h,int stride,int rg_byte_pos)257 static WEBP_INLINE void ApplyAlphaMultiply4444(uint8_t* rgba4444,
258                                                int w, int h, int stride,
259                                                int rg_byte_pos /* 0 or 1 */) {
260   while (h-- > 0) {
261     int i;
262     for (i = 0; i < w; ++i) {
263       const uint32_t rg = rgba4444[2 * i + rg_byte_pos];
264       const uint32_t ba = rgba4444[2 * i + (rg_byte_pos ^ 1)];
265       const uint8_t a = ba & 0x0f;
266       const uint32_t mult = MULTIPLIER(a);
267       const uint8_t r = multiply(dither_hi(rg), mult);
268       const uint8_t g = multiply(dither_lo(rg), mult);
269       const uint8_t b = multiply(dither_hi(ba), mult);
270       rgba4444[2 * i + rg_byte_pos] = (r & 0xf0) | ((g >> 4) & 0x0f);
271       rgba4444[2 * i + (rg_byte_pos ^ 1)] = (b & 0xf0) | a;
272     }
273     rgba4444 += stride;
274   }
275 }
276 #undef MULTIPLIER
277 
ApplyAlphaMultiply_16b(uint8_t * rgba4444,int w,int h,int stride)278 static void ApplyAlphaMultiply_16b(uint8_t* rgba4444,
279                                    int w, int h, int stride) {
280 #ifdef WEBP_SWAP_16BIT_CSP
281   ApplyAlphaMultiply4444(rgba4444, w, h, stride, 1);
282 #else
283   ApplyAlphaMultiply4444(rgba4444, w, h, stride, 0);
284 #endif
285 }
286 
DispatchAlpha_C(const uint8_t * alpha,int alpha_stride,int width,int height,uint8_t * dst,int dst_stride)287 static int DispatchAlpha_C(const uint8_t* alpha, int alpha_stride,
288                            int width, int height,
289                            uint8_t* dst, int dst_stride) {
290   uint32_t alpha_mask = 0xff;
291   int i, j;
292 
293   for (j = 0; j < height; ++j) {
294     for (i = 0; i < width; ++i) {
295       const uint32_t alpha_value = alpha[i];
296       dst[4 * i] = alpha_value;
297       alpha_mask &= alpha_value;
298     }
299     alpha += alpha_stride;
300     dst += dst_stride;
301   }
302 
303   return (alpha_mask != 0xff);
304 }
305 
DispatchAlphaToGreen_C(const uint8_t * alpha,int alpha_stride,int width,int height,uint32_t * dst,int dst_stride)306 static void DispatchAlphaToGreen_C(const uint8_t* alpha, int alpha_stride,
307                                    int width, int height,
308                                    uint32_t* dst, int dst_stride) {
309   int i, j;
310   for (j = 0; j < height; ++j) {
311     for (i = 0; i < width; ++i) {
312       dst[i] = alpha[i] << 8;  // leave A/R/B channels zero'd.
313     }
314     alpha += alpha_stride;
315     dst += dst_stride;
316   }
317 }
318 
ExtractAlpha_C(const uint8_t * argb,int argb_stride,int width,int height,uint8_t * alpha,int alpha_stride)319 static int ExtractAlpha_C(const uint8_t* argb, int argb_stride,
320                           int width, int height,
321                           uint8_t* alpha, int alpha_stride) {
322   uint8_t alpha_mask = 0xff;
323   int i, j;
324 
325   for (j = 0; j < height; ++j) {
326     for (i = 0; i < width; ++i) {
327       const uint8_t alpha_value = argb[4 * i];
328       alpha[i] = alpha_value;
329       alpha_mask &= alpha_value;
330     }
331     argb += argb_stride;
332     alpha += alpha_stride;
333   }
334   return (alpha_mask == 0xff);
335 }
336 
ExtractGreen_C(const uint32_t * argb,uint8_t * alpha,int size)337 static void ExtractGreen_C(const uint32_t* argb, uint8_t* alpha, int size) {
338   int i;
339   for (i = 0; i < size; ++i) alpha[i] = argb[i] >> 8;
340 }
341 
342 void (*WebPApplyAlphaMultiply)(uint8_t*, int, int, int, int);
343 void (*WebPApplyAlphaMultiply4444)(uint8_t*, int, int, int);
344 int (*WebPDispatchAlpha)(const uint8_t*, int, int, int, uint8_t*, int);
345 void (*WebPDispatchAlphaToGreen)(const uint8_t*, int, int, int, uint32_t*, int);
346 int (*WebPExtractAlpha)(const uint8_t*, int, int, int, uint8_t*, int);
347 void (*WebPExtractGreen)(const uint32_t* argb, uint8_t* alpha, int size);
348 
349 //------------------------------------------------------------------------------
350 // Init function
351 
352 extern void WebPInitAlphaProcessingMIPSdspR2(void);
353 extern void WebPInitAlphaProcessingSSE2(void);
354 extern void WebPInitAlphaProcessingSSE41(void);
355 extern void WebPInitAlphaProcessingNEON(void);
356 
357 static volatile VP8CPUInfo alpha_processing_last_cpuinfo_used =
358     (VP8CPUInfo)&alpha_processing_last_cpuinfo_used;
359 
WebPInitAlphaProcessing(void)360 WEBP_TSAN_IGNORE_FUNCTION void WebPInitAlphaProcessing(void) {
361   if (alpha_processing_last_cpuinfo_used == VP8GetCPUInfo) return;
362 
363   WebPMultARGBRow = WebPMultARGBRowC;
364   WebPMultRow = WebPMultRowC;
365   WebPApplyAlphaMultiply = ApplyAlphaMultiply;
366   WebPApplyAlphaMultiply4444 = ApplyAlphaMultiply_16b;
367 
368   WebPDispatchAlpha = DispatchAlpha_C;
369   WebPDispatchAlphaToGreen = DispatchAlphaToGreen_C;
370   WebPExtractAlpha = ExtractAlpha_C;
371   WebPExtractGreen = ExtractGreen_C;
372 
373   // If defined, use CPUInfo() to overwrite some pointers with faster versions.
374   if (VP8GetCPUInfo != NULL) {
375 #if defined(WEBP_USE_SSE2)
376     if (VP8GetCPUInfo(kSSE2)) {
377       WebPInitAlphaProcessingSSE2();
378 #if defined(WEBP_USE_SSE41)
379       if (VP8GetCPUInfo(kSSE4_1)) {
380         WebPInitAlphaProcessingSSE41();
381       }
382 #endif
383     }
384 #endif
385 #if defined(WEBP_USE_NEON)
386     if (VP8GetCPUInfo(kNEON)) {
387       WebPInitAlphaProcessingNEON();
388     }
389 #endif
390 #if defined(WEBP_USE_MIPS_DSP_R2)
391     if (VP8GetCPUInfo(kMIPSdspR2)) {
392       WebPInitAlphaProcessingMIPSdspR2();
393     }
394 #endif
395   }
396   alpha_processing_last_cpuinfo_used = VP8GetCPUInfo;
397 }
398