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/*
* Copyright (C) 2010-2013 Team XBMC
* http://xbmc.org
*
* 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, 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 XBMC; see the file COPYING. If not, see
* <http://www.gnu.org/licenses/>.
*
*/
#version 120
uniform sampler2D img;
uniform float m_stretch;
uniform float m_alpha;
varying vec2 m_cord;
vec2 stretch(vec2 pos)
{
// 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.
// a simple curve to do this is g(x) = b(x-0.5) + (1-b)2^(n-1)(x-0.5)^n + 0.5
// where the power preserves sign. n = 2 is the simplest non-linear case (required when b != 1)
float x = pos.x - 0.5;
return vec2(mix(x * abs(x) * 2.0, x, m_stretch) + 0.5, pos.y);
}
void main()
{
gl_FragColor.rgb = texture2D(img, stretch(m_cord)).rgb;
gl_FragColor.a = m_alpha;
}
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