LookingGlass/client/renderers/EGL/shader/downscale_lanczos2.frag

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#version 300 es
precision mediump float;
#define PI 3.141592653589793
in vec2 fragCoord;
out vec4 fragColor;
uniform sampler2D texture;
float sinc(float x)
{
return x == 0.0 ? 1.0 : sin(x * PI) / (x * PI);
}
float lanczos(float x)
{
return sinc(x) * sinc(x * 0.5);
}
float lanczos(vec2 v)
{
return lanczos(v.x) * lanczos(v.y);
}
void main()
{
vec2 size = vec2(textureSize(texture, 0));
vec2 pos = fragCoord * size;
vec2 invSize = 1.0 / size;
vec2 uvc = floor(pos) + vec2(0.5, 0.5);
vec2 uvs[9] = vec2[](
uvc + vec2(-1.0, -1.0),
uvc + vec2(-1.0, 0.0),
uvc + vec2(-1.0, 1.0),
uvc + vec2( 0.0, -1.0),
uvc + vec2( 0.0, 0.0),
uvc + vec2( 0.0, 1.0),
uvc + vec2( 1.0, -1.0),
uvc + vec2( 1.0, 0.0),
uvc + vec2( 1.0, 1.0)
);
float factors[9];
float sum = 0.0;
for (int i = 0; i < 9; ++i)
{
factors[i] = lanczos(uvs[i] - fragCoord * size);
sum += factors[i];
}
for (int i = 0; i < 9; ++i)
factors[i] /= sum;
vec3 color = vec3(0.0);
for (int i = 0; i < 9; ++i)
color += texture2D(texture, uvs[i] * invSize).rgb * factors[i];
fragColor = vec4(color, 1.0);
}