REF:  http://graphics.cs.williams.edu/papers/MedianShaderX6/
/*
3x3 Median
Morgan McGuire and Kyle Whitson
http://graphics.cs.williams.edu
*/

// Input texture
uniform sampler2D T;

#ifndef G3D
// vec2(1/width, 1/height) of the texture
    uniform vec2 Tinvsize;
#else
#    define Tinvsize g3d_sampler2DInvSize(T))
#endif 


// Change these 2 defines to change precision,
#define vec vec3
#define toVec(x) x.rgb

//#define vec vec4
//#define toVec(x) x.rgba

#define s2(a, b)		temp = a; a = min(a, b); b = max(temp, b);
#define mn3(a, b, c)		s2(a, b); s2(a, c);
#define mx3(a, b, c)		s2(b, c); s2(a, c);

#define mnmx3(a, b, c)		mx3(a, b, c); s2(a, b);                         // 3 exchanges
#define mnmx4(a, b, c, d)	s2(a, b); s2(c, d); s2(a, c); s2(b, d);         // 4 exchanges
#define mnmx5(a, b, c, d, e)	s2(a, b); s2(c, d); mn3(a, c, e); mx3(b, d, e); // 6 exchanges
#define mnmx6(a, b, c, d, e, f) s2(a, d); s2(b, e); s2(c, f); \
                                mn3(a, b, c); mx3(d, e, f);                // 7 exchanges

void main() {

  vec v[9];

  // Add the pixels which make up our window to the pixel array.
  for(int dX = -1; dX <= 1; ++dX) {
    for(int dY = -1; dY <= 1; ++dY) {		
      vec2 offset = vec2(float(dX), float(dY));
		    
      // If a pixel in the window is located at (x+dX, y+dY), 
      // put it at index (dX + R)(2R + 1) + (dY + R) of the
      // pixel array. This will fill the pixel array, 
      // with the top left pixel of the window at pixel[0] and the
      // bottom right pixel of the window at pixel[N-1].
      v[(dX + 1) * 3 + (dY + 1)] = toVec(texture2D(T, gl_TexCoord[0].xy + offset * Tinvsize));
    }
  }

  vec temp;

  // Starting with a subset of size 6, remove the min and max each time
  mnmx6(v[0], v[1], v[2], v[3], v[4], v[5]);
  mnmx5(v[1], v[2], v[3], v[4], v[6]);
  mnmx4(v[2], v[3], v[4], v[7]);
  mnmx3(v[3], v[4], v[8]);
  toVec(gl_FragColor) = v[4];

}

'Image Recognition > Fundamental' 카테고리의 다른 글

Histogram Smoothing via Bezier Curve  (1) 2010.01.10
Running Median Filter  (0) 2010.01.07
Fast Median Filter 3x3  (0) 2009.11.27
Fant's Resampling  (0) 2008.12.17
Bright Preserving Histogram Equalization with Maximum Entropy  (0) 2008.07.31
Adaptive Binarization  (1) 2008.07.14
Posted by helloktk