TwoTerm/ScanLineFilter.cikernel

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/*
* simulate scanlines by darkening every other line.
*
*/
kernel vec4 scanline(sampler image, float opacity)
{
vec2 coord = samplerCoord(image);
vec4 pixel = sample(image, coord);
float isOdd = mod(floor(coord.y), 2.0);
// isOdd == 0 --> return pixel
// isOdd == 1 --> return pixel * opacity
//float multiplier = compare(isOdd - 1.0, 1.0, opacity);
float multiplier = isOdd == 0.0 ? 1.0 : opacity;
return pixel * multiplier;
}