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uniform sampler2D img;
uniform sampler1D kernelTex;
uniform vec2 stepxy;
uniform float m_stretch;
//nvidia's half is a 16 bit float and can bring some speed improvements
//without affecting quality
#ifndef __GLSL_CG_DATA_TYPES
#define half float
#define half3 vec3
#define half4 vec4
#endif
#if (HAS_FLOAT_TEXTURE)
half3 weight(float pos)
{
return texture(kernelTex, pos).rgb;
}
#else
half3 weight(float pos)
{
return texture(kernelTex, pos).rgb * 2.0 - 1.0;
}
#endif
vec2 stretch(vec2 pos)
{
#if (XBMC_STRETCH)
// 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);
#else
return pos;
#endif
}
half3 line (vec2 pos, const int yoffset, half3 linetaps1, half3 linetaps2)
{
return
textureOffset(img, pos, ivec2(-2, yoffset)).rgb * linetaps1.r +
textureOffset(img, pos, ivec2(-1, yoffset)).rgb * linetaps2.r +
textureOffset(img, pos, ivec2( 0, yoffset)).rgb * linetaps1.g +
textureOffset(img, pos, ivec2( 1, yoffset)).rgb * linetaps2.g +
textureOffset(img, pos, ivec2( 2, yoffset)).rgb * linetaps1.b +
textureOffset(img, pos, ivec2( 3, yoffset)).rgb * linetaps2.b;
}
void main()
{
vec2 pos = stretch(gl_TexCoord[0].xy);
vec2 f = fract(pos / stepxy);
half3 linetaps1 = weight((1.0 - f.x) / 2.0);
half3 linetaps2 = weight((1.0 - f.x) / 2.0 + 0.5);
half3 columntaps1 = weight((1.0 - f.y) / 2.0);
half3 columntaps2 = weight((1.0 - f.y) / 2.0 + 0.5);
//make sure all taps added together is exactly 1.0, otherwise some (very small) distortion can occur
half sum = linetaps1.r + linetaps1.g + linetaps1.b + linetaps2.r + linetaps2.g + linetaps2.b;
linetaps1 /= sum;
linetaps2 /= sum;
sum = columntaps1.r + columntaps1.g + columntaps1.b + columntaps2.r + columntaps2.g + columntaps2.b;
columntaps1 /= sum;
columntaps2 /= sum;
vec2 xystart = (0.5 - f) * stepxy + pos;
gl_FragColor.rgb =
line(xystart, -2, linetaps1, linetaps2) * columntaps1.r +
line(xystart, -1, linetaps1, linetaps2) * columntaps2.r +
line(xystart, 0, linetaps1, linetaps2) * columntaps1.g +
line(xystart, 1, linetaps1, linetaps2) * columntaps2.g +
line(xystart, 2, linetaps1, linetaps2) * columntaps1.b +
line(xystart, 3, linetaps1, linetaps2) * columntaps2.b;
gl_FragColor.a = gl_Color.a;
}
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