denoise.frag

#version 300 es

precision highp float;
uniform vec2 uWindowSize;
uniform vec2 uTexSize;
uniform sampler2D uTex;

in vec2 vTexCoord;
out vec4 color;

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//  Copyright (c) 2018-2019 Michele Morrone
//  All rights reserved.
//
//  https://michelemorrone.eu - https://BrutPitt.com
//
//  me@michelemorrone.eu - brutpitt@gmail.com
//  twitter: @BrutPitt - github: BrutPitt
//
//  https://github.com/BrutPitt/glslSmartDeNoise/
//
//  This software is distributed under the terms of the BSD 2-Clause license
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

#define INV_SQRT_OF_2PI 0.39894228040143267793994605993439  // 1.0/SQRT_OF_2PI
#define INV_PI 0.31830988618379067153776752674503

//  smartDeNoise - parameters
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//
//  sampler2D tex     - sampler image / texture
//  vec2 uv           - actual fragment coord
//  float sigma  >  0 - sigma Standard Deviation
//  float kSigma >= 0 - sigma coefficient
//      kSigma * sigma  -->  radius of the circular kernel
//  float threshold   - edge sharpening threshold

vec4 smartDeNoise(sampler2D tex, vec2 uv, float sigma, float kSigma, float threshold) {
  float radius = round(kSigma*sigma);
  float radQ = radius * radius;

  float invSigmaQx2 = .5 / (sigma * sigma);      // 1.0 / (sigma^2 * 2.0)
  float invSigmaQx2PI = INV_PI * invSigmaQx2;    // 1.0 / (sqrt(PI) * sigma)

  float invThresholdSqx2 = .5 / (threshold * threshold);     // 1.0 / (sigma^2 * 2.0)
  float invThresholdSqrt2PI = INV_SQRT_OF_2PI / threshold;   // 1.0 / (sqrt(2*PI) * sigma)

  vec4 centrPx = texture(tex, uv);

  float zBuff = 0.0;
  vec4 aBuff = vec4(0.0);
  vec2 size = vec2(textureSize(tex, 0));

  for(float x=-radius; x <= radius; x++) {
      float pt = sqrt(radQ-x*x);  // pt = yRadius: have circular trend
      for(float y=-pt; y <= pt; y++) {
          vec2 d = vec2(x,y);
          float blurFactor = exp( -dot(d , d) * invSigmaQx2 ) * invSigmaQx2PI;
          vec4 walkPx =  texture(tex, uv + d/size);
          vec4 dC = walkPx-centrPx;
          float deltaFactor = exp( -dot(dC, dC) * invThresholdSqx2) * invThresholdSqrt2PI * blurFactor;
          zBuff += deltaFactor;
          aBuff += deltaFactor*walkPx;
      }
  }
  return aBuff/zBuff;
}

void main () {
  color = smartDeNoise(uTex, vTexCoord, 5.0, 2.0, .100);
}