ref: 4af18a71d333587d1a3f90f8f9f826d31e34cc41
dir: /vpx_dsp/add_noise.c/
/* * Copyright (c) 2015 The WebM project authors. All Rights Reserved. * * Use of this source code is governed by a BSD-style license * that can be found in the LICENSE file in the root of the source * tree. An additional intellectual property rights grant can be found * in the file PATENTS. All contributing project authors may * be found in the AUTHORS file in the root of the source tree. */ #include <math.h> #include <stdlib.h> #include "./vpx_config.h" #include "./vpx_dsp_rtcd.h" #include "vpx/vpx_integer.h" #include "vpx_dsp/postproc.h" #include "vpx_ports/mem.h" void vpx_plane_add_noise_c(uint8_t *start, const int8_t *noise, int blackclamp, int whiteclamp, int width, int height, int pitch) { int i, j; int bothclamp = blackclamp + whiteclamp; for (i = 0; i < height; ++i) { uint8_t *pos = start + i * pitch; const int8_t *ref = (const int8_t *)(noise + (rand() & 0xff)); // NOLINT for (j = 0; j < width; ++j) { int v = pos[j]; v = clamp(v - blackclamp, 0, 255); v = clamp(v + bothclamp, 0, 255); v = clamp(v - whiteclamp, 0, 255); pos[j] = v + ref[j]; } } } static double gaussian(double sigma, double mu, double x) { return 1 / (sigma * sqrt(2.0 * 3.14159265)) * (exp(-(x - mu) * (x - mu) / (2 * sigma * sigma))); } int vpx_setup_noise(double sigma, int8_t *noise, int size) { int8_t char_dist[256]; int next = 0, i, j; // set up a 256 entry lookup that matches gaussian distribution for (i = -32; i < 32; ++i) { const int a_i = (int)(0.5 + 256 * gaussian(sigma, 0, i)); if (a_i) { for (j = 0; j < a_i; ++j) { char_dist[next + j] = (int8_t)i; } next = next + j; } } // Rounding error - might mean we have less than 256. for (; next < 256; ++next) { char_dist[next] = 0; } for (i = 0; i < size; ++i) { noise[i] = char_dist[rand() & 0xff]; // NOLINT } // Returns the highest non 0 value used in distribution. return -char_dist[0]; }