1 /* 2 * Copyright (c) 2015 The WebM project authors. All Rights Reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 11 #include <math.h> 12 #include <stdlib.h> 13 14 #include "./vpx_config.h" 15 #include "./vpx_dsp_rtcd.h" 16 17 #include "vpx/vpx_integer.h" 18 #include "vpx_ports/mem.h" 19 20 void vpx_plane_add_noise_c(uint8_t *start, const int8_t *noise, int blackclamp, 21 int whiteclamp, int width, int height, int pitch) { 22 int i, j; 23 int bothclamp = blackclamp + whiteclamp; 24 for (i = 0; i < height; ++i) { 25 uint8_t *pos = start + i * pitch; 26 const int8_t *ref = (const int8_t *)(noise + (rand() & 0xff)); // NOLINT 27 28 for (j = 0; j < width; ++j) { 29 int v = pos[j]; 30 31 v = clamp(v - blackclamp, 0, 255); 32 v = clamp(v + bothclamp, 0, 255); 33 v = clamp(v - whiteclamp, 0, 255); 34 35 pos[j] = v + ref[j]; 36 } 37 } 38 } 39 40 static double gaussian(double sigma, double mu, double x) { 41 return 1 / (sigma * sqrt(2.0 * 3.14159265)) * 42 (exp(-(x - mu) * (x - mu) / (2 * sigma * sigma))); 43 } 44 45 int vpx_setup_noise(double sigma, int8_t *noise, int size) { 46 int8_t char_dist[256]; 47 int next = 0, i, j; 48 49 // set up a 256 entry lookup that matches gaussian distribution 50 for (i = -32; i < 32; ++i) { 51 const int a_i = (int)(0.5 + 256 * gaussian(sigma, 0, i)); 52 if (a_i) { 53 for (j = 0; j < a_i; ++j) { 54 char_dist[next + j] = (int8_t)i; 55 } 56 next = next + j; 57 } 58 } 59 60 // Rounding error - might mean we have less than 256. 61 for (; next < 256; ++next) { 62 char_dist[next] = 0; 63 } 64 65 for (i = 0; i < size; ++i) { 66 noise[i] = char_dist[rand() & 0xff]; // NOLINT 67 } 68 69 // Returns the highest non 0 value used in distribution. 70 return -char_dist[0]; 71 } 72
