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