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/* Preprocess the input of the blur filter by squaring it in its alpha straight form, assuming the
* given color is alpha premultiplied. */
vec4 gamma_correct_blur_input(vec4 color)
{
/* Unpremultiply alpha. */
color.rgb /= color.a > 0.0 ? color.a : 1.0;
/* Square color channel if it is positive, otherwise zero it. */
color.rgb *= mix(color.rgb, vec3(0.0), lessThan(color.rgb, vec3(0.0)));
/* Premultiply alpha to undo previous alpha unpremultiplication. */
color.rgb *= color.a > 0.0 ? color.a : 1.0;
return color;
}
/* Postprocess the output of the blur filter by taking its square root it in its alpha straight
* form, assuming the given color is alpha premultiplied. This essential undoes the processing done
* by the gamma_correct_blur_input function. */
vec4 gamma_uncorrect_blur_output(vec4 color)
{
/* Unpremultiply alpha. */
color.rgb /= color.a > 0.0 ? color.a : 1.0;
/* Take the square root of the color channel if it is positive, otherwise zero it. */
color.rgb = mix(sqrt(color.rgb), vec3(0.0), lessThan(color.rgb, vec3(0.0)));
/* Premultiply alpha to undo previous alpha unpremultiplication. */
color.rgb *= color.a > 0.0 ? color.a : 1.0;
return color;
}
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