random_utils.c (1863B)
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 // Pseudo-random utilities 11 // 12 // Author: Skal (pascal.massimino@gmail.com) 13 14 #include <string.h> 15 16 #include "src/webp/types.h" 17 #include "src/utils/random_utils.h" 18 19 //------------------------------------------------------------------------------ 20 21 // 31b-range values 22 static const uint32_t kRandomTable[VP8_RANDOM_TABLE_SIZE] = { 23 0x0de15230, 0x03b31886, 0x775faccb, 0x1c88626a, 0x68385c55, 0x14b3b828, 24 0x4a85fef8, 0x49ddb84b, 0x64fcf397, 0x5c550289, 0x4a290000, 0x0d7ec1da, 25 0x5940b7ab, 0x5492577d, 0x4e19ca72, 0x38d38c69, 0x0c01ee65, 0x32a1755f, 26 0x5437f652, 0x5abb2c32, 0x0faa57b1, 0x73f533e7, 0x685feeda, 0x7563cce2, 27 0x6e990e83, 0x4730a7ed, 0x4fc0d9c6, 0x496b153c, 0x4f1403fa, 0x541afb0c, 28 0x73990b32, 0x26d7cb1c, 0x6fcc3706, 0x2cbb77d8, 0x75762f2a, 0x6425ccdd, 29 0x24b35461, 0x0a7d8715, 0x220414a8, 0x141ebf67, 0x56b41583, 0x73e502e3, 30 0x44cab16f, 0x28264d42, 0x73baaefb, 0x0a50ebed, 0x1d6ab6fb, 0x0d3ad40b, 31 0x35db3b68, 0x2b081e83, 0x77ce6b95, 0x5181e5f0, 0x78853bbc, 0x009f9494, 32 0x27e5ed3c 33 }; 34 35 void VP8InitRandom(VP8Random* const rg, float dithering) { 36 memcpy(rg->tab, kRandomTable, sizeof(rg->tab)); 37 rg->index1 = 0; 38 rg->index2 = 31; 39 rg->amp = (dithering < 0.0) ? 0 40 : (dithering > 1.0) ? (1 << VP8_RANDOM_DITHER_FIX) 41 : (uint32_t)((1 << VP8_RANDOM_DITHER_FIX) * dithering); 42 } 43 44 //------------------------------------------------------------------------------