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/*
* 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) {
if (next + j >= 256) goto set_noise;
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;
}
set_noise:
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];
}
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