/system/shaders/convolution-6x6.glsl

  1/*
  2 *      Copyright (C) 2010-2013 Team XBMC
  3 *      http://xbmc.org
  4 *
  5 *  This Program is free software; you can redistribute it and/or modify
  6 *  it under the terms of the GNU General Public License as published by
  7 *  the Free Software Foundation; either version 2, or (at your option)
  8 *  any later version.
  9 *
 10 *  This Program is distributed in the hope that it will be useful,
 11 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 12 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 13 *  GNU General Public License for more details.
 14 *
 15 *  You should have received a copy of the GNU General Public License
 16 *  along with XBMC; see the file COPYING.  If not, see
 17 *  <http://www.gnu.org/licenses/>.
 18 *
 19 */
 20
 21uniform sampler2D img;
 22uniform vec2      stepxy;
 23uniform float     m_stretch;
 24varying vec2      cord;
 25
 26#if (USE1DTEXTURE)
 27  uniform sampler1D kernelTex;
 28#else
 29  uniform sampler2D kernelTex;
 30#endif
 31
 32//nvidia's half is a 16 bit float and can bring some speed improvements
 33//without affecting quality
 34#ifndef __GLSL_CG_DATA_TYPES
 35  #define half float
 36  #define half3 vec3
 37  #define half4 vec4
 38#endif
 39
 40half3 weight(float pos)
 41{
 42#if (HAS_FLOAT_TEXTURE)
 43  #if (USE1DTEXTURE)
 44    return texture1D(kernelTex, pos).rgb;
 45  #else
 46    return texture2D(kernelTex, vec2(pos, 0.5)).rgb;
 47  #endif
 48#else
 49  #if (USE1DTEXTURE)
 50    return texture1D(kernelTex, pos).rgb * 2.0 - 1.0;
 51  #else
 52    return texture2D(kernelTex, vec2(pos, 0.5)).rgb * 2.0 - 1.0;
 53  #endif
 54#endif
 55}
 56
 57vec2 stretch(vec2 pos)
 58{
 59#if (XBMC_STRETCH)
 60  // our transform should map [0..1] to itself, with f(0) = 0, f(1) = 1, f(0.5) = 0.5, and f'(0.5) = b.
 61  // a simple curve to do this is g(x) = b(x-0.5) + (1-b)2^(n-1)(x-0.5)^n + 0.5
 62  // where the power preserves sign. n = 2 is the simplest non-linear case (required when b != 1)
 63  float x = pos.x - 0.5;
 64  return vec2(mix(x * abs(x) * 2.0, x, m_stretch) + 0.5, pos.y);
 65#else
 66  return pos;
 67#endif
 68}
 69
 70half3 pixel(float xpos, float ypos)
 71{
 72  return texture2D(img, vec2(xpos, ypos)).rgb;
 73}
 74
 75half3 line (float ypos, vec3 xpos1, vec3 xpos2, half3 linetaps1, half3 linetaps2)
 76{
 77  return
 78    pixel(xpos1.r, ypos) * linetaps1.r +
 79    pixel(xpos1.g, ypos) * linetaps2.r +
 80    pixel(xpos1.b, ypos) * linetaps1.g +
 81    pixel(xpos2.r, ypos) * linetaps2.g +
 82    pixel(xpos2.g, ypos) * linetaps1.b +
 83    pixel(xpos2.b, ypos) * linetaps2.b; 
 84}
 85
 86vec4 process()
 87{
 88  vec4 rgb;
 89  vec2 pos = stretch(cord) + stepxy * 0.5;
 90  vec2 f = fract(pos / stepxy);
 91
 92  half3 linetaps1   = weight((1.0 - f.x) / 2.0);
 93  half3 linetaps2   = weight((1.0 - f.x) / 2.0 + 0.5);
 94  half3 columntaps1 = weight((1.0 - f.y) / 2.0);
 95  half3 columntaps2 = weight((1.0 - f.y) / 2.0 + 0.5);
 96
 97  //make sure all taps added together is exactly 1.0, otherwise some (very small) distortion can occur
 98  half sum = linetaps1.r + linetaps1.g + linetaps1.b + linetaps2.r + linetaps2.g + linetaps2.b;
 99  linetaps1 /= sum;
100  linetaps2 /= sum;
101  sum = columntaps1.r + columntaps1.g + columntaps1.b + columntaps2.r + columntaps2.g + columntaps2.b;
102  columntaps1 /= sum;
103  columntaps2 /= sum;
104
105  vec2 xystart = (-2.5 - f) * stepxy + pos;
106  vec3 xpos1 = vec3(xystart.x, xystart.x + stepxy.x, xystart.x + stepxy.x * 2.0);
107  vec3 xpos2 = vec3(xystart.x + stepxy.x * 3.0, xystart.x + stepxy.x * 4.0, xystart.x + stepxy.x * 5.0);
108
109  rgb =
110   line(xystart.y                 , xpos1, xpos2, linetaps1, linetaps2) * columntaps1.r +
111   line(xystart.y + stepxy.y      , xpos1, xpos2, linetaps1, linetaps2) * columntaps2.r +
112   line(xystart.y + stepxy.y * 2.0, xpos1, xpos2, linetaps1, linetaps2) * columntaps1.g +
113   line(xystart.y + stepxy.y * 3.0, xpos1, xpos2, linetaps1, linetaps2) * columntaps2.g +
114   line(xystart.y + stepxy.y * 4.0, xpos1, xpos2, linetaps1, linetaps2) * columntaps1.b +
115   line(xystart.y + stepxy.y * 5.0, xpos1, xpos2, linetaps1, linetaps2) * columntaps2.b;
116
117  rgb.a = gl_Color.a;
118  return rgb;
119}
120