2 * Copyright (C) 2010-2013 Team XBMC
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)
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.
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/>.
21 uniform sampler2D img;
22 uniform float m_stretch;
25 vec2 stretch(vec2 pos)
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);
36 gl_FragColor.rgb = texture2D(img, stretch(cord)).rgb;
37 gl_FragColor.a = gl_Color.a;