/system/shaders/stretch.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 float     m_stretch;
23varying vec2      cord;
24
25vec2 stretch(vec2 pos)
26{
27  // 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.
28  // a simple curve to do this is g(x) = b(x-0.5) + (1-b)2^(n-1)(x-0.5)^n + 0.5
29  // where the power preserves sign. n = 2 is the simplest non-linear case (required when b != 1)
30  float x = pos.x - 0.5;
31  return vec2(mix(x * abs(x) * 2.0, x, m_stretch) + 0.5, pos.y);
32}
33
34void main()
35{
36  gl_FragColor.rgb = texture2D(img, stretch(cord)).rgb;
37  gl_FragColor.a = gl_Color.a;
38}
39