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uniform sampler2D img;
uniform float stepx;
uniform float stepy;
uniform sampler2D kernelTex;
vec4 cubicFilter(float xValue, vec4 c0, vec4 c1, vec4 c2, vec4 c3)
{
vec4 h = texture2D(kernelTex, vec2(xValue, 0.5));
vec4 r = c0 * h.r;
r += c1 * h.g;
r += c2 * h.b;
r += c3 * h.a;
return r;
}
void main()
{
vec2 f = vec2(gl_TexCoord[0].x / stepx , gl_TexCoord[0].y / stepy);
f = fract(f);
vec4 t0 = cubicFilter(f.x,
texture2D(img, gl_TexCoord[0].xy + vec2(-stepx, -stepy)),
texture2D(img, gl_TexCoord[0].xy + vec2(0.0, -stepy)),
texture2D(img, gl_TexCoord[0].xy + vec2(stepx, -stepy)),
texture2D(img, gl_TexCoord[0].xy + vec2(2.0*stepx, -stepy)));
vec4 t1 = cubicFilter(f.x,
texture2D(img, gl_TexCoord[0].xy + vec2(-stepx, 0.0)),
texture2D(img, gl_TexCoord[0].xy + vec2(0.0, 0.0)),
texture2D(img, gl_TexCoord[0].xy + vec2(stepx, 0.0)),
texture2D(img, gl_TexCoord[0].xy + vec2(2.0*stepx, 0.0)));
vec4 t2 = cubicFilter(f.x,
texture2D(img, gl_TexCoord[0].xy + vec2(-stepx, stepy)),
texture2D(img, gl_TexCoord[0].xy + vec2(0.0, stepy)),
texture2D(img, gl_TexCoord[0].xy + vec2(stepx, stepy)),
texture2D(img, gl_TexCoord[0].xy + vec2(2.0*stepx, stepy)));
vec4 t3 = cubicFilter(f.x,
texture2D(img, gl_TexCoord[0].xy + vec2(-stepx, 2.0*stepy)),
texture2D(img, gl_TexCoord[0].xy + vec2(0, 2.0*stepy)),
texture2D(img, gl_TexCoord[0].xy + vec2(stepx, 2.0*stepy)),
texture2D(img, gl_TexCoord[0].xy + vec2(2.0*stepx, 2.0*stepy)));
gl_FragColor = cubicFilter(f.y, t0, t1, t2, t3);
gl_FragColor.a = gl_Color.a;
}
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