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_dsp/postproc.h"
19#include "vpx_ports/mem.h"
20
21void vpx_plane_add_noise_c(uint8_t *start, const int8_t *noise, int blackclamp,
22                           int whiteclamp, int width, int height, int pitch) {
23  int i, j;
24  int bothclamp = blackclamp + whiteclamp;
25  for (i = 0; i < height; ++i) {
26    uint8_t *pos = start + i * pitch;
27    const int8_t *ref = (const int8_t *)(noise + (rand() & 0xff));  // NOLINT
28
29    for (j = 0; j < width; ++j) {
30      int v = pos[j];
31
32      v = clamp(v - blackclamp, 0, 255);
33      v = clamp(v + bothclamp, 0, 255);
34      v = clamp(v - whiteclamp, 0, 255);
35
36      pos[j] = v + ref[j];
37    }
38  }
39}
40
41static double gaussian(double sigma, double mu, double x) {
42  return 1 / (sigma * sqrt(2.0 * 3.14159265)) *
43         (exp(-(x - mu) * (x - mu) / (2 * sigma * sigma)));
44}
45
46int vpx_setup_noise(double sigma, int8_t *noise, int size) {
47  int8_t char_dist[256];
48  int next = 0, i, j;
49
50  // set up a 256 entry lookup that matches gaussian distribution
51  for (i = -32; i < 32; ++i) {
52    const int a_i = (int)(0.5 + 256 * gaussian(sigma, 0, i));
53    if (a_i) {
54      for (j = 0; j < a_i; ++j) {
55        char_dist[next + j] = (int8_t)i;
56      }
57      next = next + j;
58    }
59  }
60
61  // Rounding error - might mean we have less than 256.
62  for (; next < 256; ++next) {
63    char_dist[next] = 0;
64  }
65
66  for (i = 0; i < size; ++i) {
67    noise[i] = char_dist[rand() & 0xff];  // NOLINT
68  }
69
70  // Returns the highest non 0 value used in distribution.
71  return -char_dist[0];
72}
73