197 lines
9.4 KiB
C
197 lines
9.4 KiB
C
// Copyright 2013 Google Inc. All Rights Reserved.
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//
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// Use of this source code is governed by a BSD-style license
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// that can be found in the COPYING file in the root of the source
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// tree. An additional intellectual property rights grant can be found
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// in the file PATENTS. All contributing project authors may
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// be found in the AUTHORS file in the root of the source tree.
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// -----------------------------------------------------------------------------
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//
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// Utilities for processing transparent channel.
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//
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// Author: Skal (pascal.massimino@gmail.com)
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#include <assert.h>
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#include "./alpha_processing.h"
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// Tables can be faster on some platform but incur some extra binary size (~2k).
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// #define USE_TABLES_FOR_ALPHA_MULT
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// -----------------------------------------------------------------------------
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#define MFIX 24 // 24bit fixed-point arithmetic
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#define HALF ((1u << MFIX) >> 1)
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#define KINV_255 ((1u << MFIX) / 255u)
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static uint32_t Mult(uint8_t x, uint32_t mult) {
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const uint32_t v = (x * mult + HALF) >> MFIX;
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assert(v <= 255); // <- 24bit precision is enough to ensure that.
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return v;
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}
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#ifdef USE_TABLES_FOR_ALPHA_MULT
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static const uint32_t kMultTables[2][256] = {
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{ // (255u << MFIX) / alpha
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0x00000000, 0xff000000, 0x7f800000, 0x55000000, 0x3fc00000, 0x33000000,
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0x2a800000, 0x246db6db, 0x1fe00000, 0x1c555555, 0x19800000, 0x172e8ba2,
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0x15400000, 0x139d89d8, 0x1236db6d, 0x11000000, 0x0ff00000, 0x0f000000,
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0x0e2aaaaa, 0x0d6bca1a, 0x0cc00000, 0x0c249249, 0x0b9745d1, 0x0b1642c8,
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0x0aa00000, 0x0a333333, 0x09cec4ec, 0x0971c71c, 0x091b6db6, 0x08cb08d3,
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0x08800000, 0x0839ce73, 0x07f80000, 0x07ba2e8b, 0x07800000, 0x07492492,
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0x07155555, 0x06e45306, 0x06b5e50d, 0x0689d89d, 0x06600000, 0x063831f3,
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0x06124924, 0x05ee23b8, 0x05cba2e8, 0x05aaaaaa, 0x058b2164, 0x056cefa8,
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0x05500000, 0x05343eb1, 0x05199999, 0x05000000, 0x04e76276, 0x04cfb2b7,
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0x04b8e38e, 0x04a2e8ba, 0x048db6db, 0x0479435e, 0x04658469, 0x045270d0,
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0x04400000, 0x042e29f7, 0x041ce739, 0x040c30c3, 0x03fc0000, 0x03ec4ec4,
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0x03dd1745, 0x03ce540f, 0x03c00000, 0x03b21642, 0x03a49249, 0x03976fc6,
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0x038aaaaa, 0x037e3f1f, 0x03722983, 0x03666666, 0x035af286, 0x034fcace,
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0x0344ec4e, 0x033a5440, 0x03300000, 0x0325ed09, 0x031c18f9, 0x0312818a,
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0x03092492, 0x03000000, 0x02f711dc, 0x02ee5846, 0x02e5d174, 0x02dd7baf,
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0x02d55555, 0x02cd5cd5, 0x02c590b2, 0x02bdef7b, 0x02b677d4, 0x02af286b,
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0x02a80000, 0x02a0fd5c, 0x029a1f58, 0x029364d9, 0x028ccccc, 0x0286562d,
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0x02800000, 0x0279c952, 0x0273b13b, 0x026db6db, 0x0267d95b, 0x026217ec,
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0x025c71c7, 0x0256e62a, 0x0251745d, 0x024c1bac, 0x0246db6d, 0x0241b2f9,
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0x023ca1af, 0x0237a6f4, 0x0232c234, 0x022df2df, 0x02293868, 0x02249249,
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0x02200000, 0x021b810e, 0x021714fb, 0x0212bb51, 0x020e739c, 0x020a3d70,
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0x02061861, 0x02020408, 0x01fe0000, 0x01fa0be8, 0x01f62762, 0x01f25213,
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0x01ee8ba2, 0x01ead3ba, 0x01e72a07, 0x01e38e38, 0x01e00000, 0x01dc7f10,
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0x01d90b21, 0x01d5a3e9, 0x01d24924, 0x01cefa8d, 0x01cbb7e3, 0x01c880e5,
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0x01c55555, 0x01c234f7, 0x01bf1f8f, 0x01bc14e5, 0x01b914c1, 0x01b61eed,
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0x01b33333, 0x01b05160, 0x01ad7943, 0x01aaaaaa, 0x01a7e567, 0x01a5294a,
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0x01a27627, 0x019fcbd2, 0x019d2a20, 0x019a90e7, 0x01980000, 0x01957741,
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0x0192f684, 0x01907da4, 0x018e0c7c, 0x018ba2e8, 0x018940c5, 0x0186e5f0,
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0x01849249, 0x018245ae, 0x01800000, 0x017dc11f, 0x017b88ee, 0x0179574e,
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0x01772c23, 0x01750750, 0x0172e8ba, 0x0170d045, 0x016ebdd7, 0x016cb157,
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0x016aaaaa, 0x0168a9b9, 0x0166ae6a, 0x0164b8a7, 0x0162c859, 0x0160dd67,
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0x015ef7bd, 0x015d1745, 0x015b3bea, 0x01596596, 0x01579435, 0x0155c7b4,
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0x01540000, 0x01523d03, 0x01507eae, 0x014ec4ec, 0x014d0fac, 0x014b5edc,
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0x0149b26c, 0x01480a4a, 0x01466666, 0x0144c6af, 0x01432b16, 0x0141938b,
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0x01400000, 0x013e7063, 0x013ce4a9, 0x013b5cc0, 0x0139d89d, 0x01385830,
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0x0136db6d, 0x01356246, 0x0133ecad, 0x01327a97, 0x01310bf6, 0x012fa0be,
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0x012e38e3, 0x012cd459, 0x012b7315, 0x012a150a, 0x0128ba2e, 0x01276276,
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0x01260dd6, 0x0124bc44, 0x01236db6, 0x01222222, 0x0120d97c, 0x011f93bc,
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0x011e50d7, 0x011d10c4, 0x011bd37a, 0x011a98ef, 0x0119611a, 0x01182bf2,
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0x0116f96f, 0x0115c988, 0x01149c34, 0x0113716a, 0x01124924, 0x01112358,
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0x01100000, 0x010edf12, 0x010dc087, 0x010ca458, 0x010b8a7d, 0x010a72f0,
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0x01095da8, 0x01084a9f, 0x010739ce, 0x01062b2e, 0x01051eb8, 0x01041465,
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0x01030c30, 0x01020612, 0x01010204, 0x01000000 },
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{ // alpha * KINV_255
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0x00000000, 0x00010101, 0x00020202, 0x00030303, 0x00040404, 0x00050505,
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0x00060606, 0x00070707, 0x00080808, 0x00090909, 0x000a0a0a, 0x000b0b0b,
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0x000c0c0c, 0x000d0d0d, 0x000e0e0e, 0x000f0f0f, 0x00101010, 0x00111111,
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0x00121212, 0x00131313, 0x00141414, 0x00151515, 0x00161616, 0x00171717,
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0x00181818, 0x00191919, 0x001a1a1a, 0x001b1b1b, 0x001c1c1c, 0x001d1d1d,
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0x001e1e1e, 0x001f1f1f, 0x00202020, 0x00212121, 0x00222222, 0x00232323,
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0x00242424, 0x00252525, 0x00262626, 0x00272727, 0x00282828, 0x00292929,
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0x002a2a2a, 0x002b2b2b, 0x002c2c2c, 0x002d2d2d, 0x002e2e2e, 0x002f2f2f,
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0x00303030, 0x00313131, 0x00323232, 0x00333333, 0x00343434, 0x00353535,
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0x00363636, 0x00373737, 0x00383838, 0x00393939, 0x003a3a3a, 0x003b3b3b,
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0x003c3c3c, 0x003d3d3d, 0x003e3e3e, 0x003f3f3f, 0x00404040, 0x00414141,
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0x00424242, 0x00434343, 0x00444444, 0x00454545, 0x00464646, 0x00474747,
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0x00484848, 0x00494949, 0x004a4a4a, 0x004b4b4b, 0x004c4c4c, 0x004d4d4d,
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0x004e4e4e, 0x004f4f4f, 0x00505050, 0x00515151, 0x00525252, 0x00535353,
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0x00545454, 0x00555555, 0x00565656, 0x00575757, 0x00585858, 0x00595959,
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0x005a5a5a, 0x005b5b5b, 0x005c5c5c, 0x005d5d5d, 0x005e5e5e, 0x005f5f5f,
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0x00606060, 0x00616161, 0x00626262, 0x00636363, 0x00646464, 0x00656565,
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0x00666666, 0x00676767, 0x00686868, 0x00696969, 0x006a6a6a, 0x006b6b6b,
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0x006c6c6c, 0x006d6d6d, 0x006e6e6e, 0x006f6f6f, 0x00707070, 0x00717171,
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0x00727272, 0x00737373, 0x00747474, 0x00757575, 0x00767676, 0x00777777,
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0x00787878, 0x00797979, 0x007a7a7a, 0x007b7b7b, 0x007c7c7c, 0x007d7d7d,
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0x007e7e7e, 0x007f7f7f, 0x00808080, 0x00818181, 0x00828282, 0x00838383,
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0x00848484, 0x00858585, 0x00868686, 0x00878787, 0x00888888, 0x00898989,
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0x008a8a8a, 0x008b8b8b, 0x008c8c8c, 0x008d8d8d, 0x008e8e8e, 0x008f8f8f,
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0x00909090, 0x00919191, 0x00929292, 0x00939393, 0x00949494, 0x00959595,
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0x00969696, 0x00979797, 0x00989898, 0x00999999, 0x009a9a9a, 0x009b9b9b,
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0x009c9c9c, 0x009d9d9d, 0x009e9e9e, 0x009f9f9f, 0x00a0a0a0, 0x00a1a1a1,
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0x00a2a2a2, 0x00a3a3a3, 0x00a4a4a4, 0x00a5a5a5, 0x00a6a6a6, 0x00a7a7a7,
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0x00a8a8a8, 0x00a9a9a9, 0x00aaaaaa, 0x00ababab, 0x00acacac, 0x00adadad,
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0x00aeaeae, 0x00afafaf, 0x00b0b0b0, 0x00b1b1b1, 0x00b2b2b2, 0x00b3b3b3,
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0x00b4b4b4, 0x00b5b5b5, 0x00b6b6b6, 0x00b7b7b7, 0x00b8b8b8, 0x00b9b9b9,
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0x00bababa, 0x00bbbbbb, 0x00bcbcbc, 0x00bdbdbd, 0x00bebebe, 0x00bfbfbf,
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0x00c0c0c0, 0x00c1c1c1, 0x00c2c2c2, 0x00c3c3c3, 0x00c4c4c4, 0x00c5c5c5,
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0x00c6c6c6, 0x00c7c7c7, 0x00c8c8c8, 0x00c9c9c9, 0x00cacaca, 0x00cbcbcb,
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0x00cccccc, 0x00cdcdcd, 0x00cecece, 0x00cfcfcf, 0x00d0d0d0, 0x00d1d1d1,
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0x00d2d2d2, 0x00d3d3d3, 0x00d4d4d4, 0x00d5d5d5, 0x00d6d6d6, 0x00d7d7d7,
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0x00d8d8d8, 0x00d9d9d9, 0x00dadada, 0x00dbdbdb, 0x00dcdcdc, 0x00dddddd,
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0x00dedede, 0x00dfdfdf, 0x00e0e0e0, 0x00e1e1e1, 0x00e2e2e2, 0x00e3e3e3,
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0x00e4e4e4, 0x00e5e5e5, 0x00e6e6e6, 0x00e7e7e7, 0x00e8e8e8, 0x00e9e9e9,
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0x00eaeaea, 0x00ebebeb, 0x00ececec, 0x00ededed, 0x00eeeeee, 0x00efefef,
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0x00f0f0f0, 0x00f1f1f1, 0x00f2f2f2, 0x00f3f3f3, 0x00f4f4f4, 0x00f5f5f5,
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0x00f6f6f6, 0x00f7f7f7, 0x00f8f8f8, 0x00f9f9f9, 0x00fafafa, 0x00fbfbfb,
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0x00fcfcfc, 0x00fdfdfd, 0x00fefefe, 0x00ffffff }
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};
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static WEBP_INLINE uint32_t GetScale(uint32_t a, int inverse) {
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return kMultTables[!inverse][a];
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}
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#else
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static WEBP_INLINE uint32_t GetScale(uint32_t a, int inverse) {
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return inverse ? (255u << MFIX) / a : a * KINV_255;
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}
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#endif // USE_TABLES_FOR_ALPHA_MULT
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void WebPMultARGBRow(uint32_t* const ptr, int width, int inverse) {
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int x;
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for (x = 0; x < width; ++x) {
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const uint32_t argb = ptr[x];
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if (argb < 0xff000000u) { // alpha < 255
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if (argb <= 0x00ffffffu) { // alpha == 0
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ptr[x] = 0;
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} else {
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const uint32_t alpha = (argb >> 24) & 0xff;
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const uint32_t scale = GetScale(alpha, inverse);
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uint32_t out = argb & 0xff000000u;
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out |= Mult(argb >> 0, scale) << 0;
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out |= Mult(argb >> 8, scale) << 8;
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out |= Mult(argb >> 16, scale) << 16;
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ptr[x] = out;
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}
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}
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}
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}
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void WebPMultARGBRows(uint8_t* ptr, int stride, int width, int num_rows,
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int inverse) {
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int n;
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for (n = 0; n < num_rows; ++n) {
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WebPMultARGBRow((uint32_t*)ptr, width, inverse);
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ptr += stride;
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}
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}
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void WebPMultRow(uint8_t* const ptr, const uint8_t* const alpha,
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int width, int inverse) {
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int x;
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for (x = 0; x < width; ++x) {
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const uint32_t a = alpha[x];
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if (a != 255) {
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if (a == 0) {
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ptr[x] = 0;
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} else {
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const uint32_t scale = GetScale(a, inverse);
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ptr[x] = Mult(ptr[x], scale);
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}
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}
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}
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}
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void WebPMultRows(uint8_t* ptr, int stride,
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const uint8_t* alpha, int alpha_stride,
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int width, int num_rows, int inverse) {
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int n;
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for (n = 0; n < num_rows; ++n) {
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WebPMultRow(ptr, alpha, width, inverse);
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ptr += stride;
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alpha += alpha_stride;
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}
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}
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#undef KINV_255
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#undef HALF
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#undef MFIX
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