HQ4X.GLSL

//
// 4xGLSL HqFilter shader
//
// Copyright (C) 2005 guest(r) - guest.r@gmail.com
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
//

#if defined(VERTEX)

    uniform vec2 TextureSize;

    void main()
    {
      float x = 0.5 / TextureSize.x;
      float y = 0.5 / TextureSize.y;

      vec2 dg1 = vec2( x,y);
      vec2 dg2 = vec2(-x,y);
      vec2 sd1 = dg1*0.5;
      vec2 sd2 = dg2*0.5;
      vec2 ddx = vec2(x,0.0);
      vec2 ddy = vec2(0.0,y);

      gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
      gl_TexCoord[0] = gl_MultiTexCoord0;
      gl_TexCoord[1].xy = gl_TexCoord[0].xy - sd1;
      gl_TexCoord[2].xy = gl_TexCoord[0].xy - sd2;
      gl_TexCoord[3].xy = gl_TexCoord[0].xy + sd1;
      gl_TexCoord[4].xy = gl_TexCoord[0].xy + sd2;
      gl_TexCoord[5].xy = gl_TexCoord[0].xy - dg1;
      gl_TexCoord[6].xy = gl_TexCoord[0].xy + dg1;
      gl_TexCoord[5].zw = gl_TexCoord[0].xy - dg2;
      gl_TexCoord[6].zw = gl_TexCoord[0].xy + dg2;
      gl_TexCoord[1].zw = gl_TexCoord[0].xy - ddy;
      gl_TexCoord[2].zw = gl_TexCoord[0].xy + ddx;
      gl_TexCoord[3].zw = gl_TexCoord[0].xy + ddy;
      gl_TexCoord[4].zw = gl_TexCoord[0].xy - ddx;
    }

#elif defined(FRAGMENT)

    uniform sampler2D Texture;

    const float mx = 1.00;      // start smoothing wt.
    const float k = -1.10;      // wt. decrease factor
    const float max_w = 0.75;   // max filter weigth
    const float min_w = 0.03;   // min filter weigth
    const float lum_add = 0.33; // effects smoothing

    void main()
    {
      vec3 c  = texture2D(Texture, gl_TexCoord[0].xy).xyz;
      vec3 i1 = texture2D(Texture, gl_TexCoord[1].xy).xyz;
      vec3 i2 = texture2D(Texture, gl_TexCoord[2].xy).xyz;
      vec3 i3 = texture2D(Texture, gl_TexCoord[3].xy).xyz;
      vec3 i4 = texture2D(Texture, gl_TexCoord[4].xy).xyz;
      vec3 o1 = texture2D(Texture, gl_TexCoord[5].xy).xyz;
      vec3 o3 = texture2D(Texture, gl_TexCoord[6].xy).xyz;
      vec3 o2 = texture2D(Texture, gl_TexCoord[5].zw).xyz;
      vec3 o4 = texture2D(Texture, gl_TexCoord[6].zw).xyz;
      vec3 s1 = texture2D(Texture, gl_TexCoord[1].zw).xyz;
      vec3 s2 = texture2D(Texture, gl_TexCoord[2].zw).xyz;
      vec3 s3 = texture2D(Texture, gl_TexCoord[3].zw).xyz;
      vec3 s4 = texture2D(Texture, gl_TexCoord[4].zw).xyz;
      vec3 dt = vec3(1.0,1.0,1.0);

      float ko1=dot(abs(o1-c),dt);
      float ko2=dot(abs(o2-c),dt);
      float ko3=dot(abs(o3-c),dt);
      float ko4=dot(abs(o4-c),dt);

      float k1=min(dot(abs(i1-i3),dt),max(ko1,ko3));
      float k2=min(dot(abs(i2-i4),dt),max(ko2,ko4));

      float w1 = k2; if(ko3<ko1) w1*=ko3/ko1;
      float w2 = k1; if(ko4<ko2) w2*=ko4/ko2;
      float w3 = k2; if(ko1<ko3) w3*=ko1/ko3;
      float w4 = k1; if(ko2<ko4) w4*=ko2/ko4;

      c = (w1*o1+w2*o2+w3*o3+w4*o4+0.001*c)/(w1+w2+w3+w4+0.001);

      w1 = k*dot(abs(i1-c)+abs(i3-c),dt)/(0.125*dot(i1+i3,dt)+lum_add);
      w2 = k*dot(abs(i2-c)+abs(i4-c),dt)/(0.125*dot(i2+i4,dt)+lum_add);
      w3 = k*dot(abs(s1-c)+abs(s3-c),dt)/(0.125*dot(s1+s3,dt)+lum_add);
      w4 = k*dot(abs(s2-c)+abs(s4-c),dt)/(0.125*dot(s2+s4,dt)+lum_add);

      w1 = clamp(w1+mx,min_w,max_w);
      w2 = clamp(w2+mx,min_w,max_w);
      w3 = clamp(w3+mx,min_w,max_w);
      w4 = clamp(w4+mx,min_w,max_w);

      gl_FragColor.xyz = (w1*(i1+i3)+w2*(i2+i4)+w3*(s1+s3)+w4*(s2+s4)+c)/(2.0*(w1+w2+w3+w4)+1.0);
      gl_FragColor.a = 1.0;
    }

#endif