Off the top of my head (i.e. untested, but it should work ;) :
vec4 newpix = sample(image, samplerCoord(image));
return (newpix.r + newpix.g + newpix.b)/3.0 > threshold?
(newpix - threshold) / (1.0 - threshold) :
vec4(0.0,0.0,0.0,1.0);
(It first tests if r+g+b/3 is greater than the threshold. If it is, it reduces the value by the threshold value and then scales to 1.0, if not it returns black.)
Chris
2008/10/16 Jesse Lucas
<email@hidden>
Hi List,
I'm trying to create a kind of threshold effect, but I'm very new to CI coding. Here's what I'm trying to achieve:
-I need to change all pixels under a certain brightness value to black.
- And remap the brightness of the remain pixels to a 0 to 1 range (so I get contrast even on high threshold values).
- It doesn't matter if the resulting output is grayscale, I don't need the color information.
It is definitely not working right now so I need your help :)
Here's the code I've got for now (and I've attached the simple patch)
:
kernel vec4 threshhold(sampler image, float threshold)
{
vec4 newpix = sample(image, samplerCoord(image));
vec4 newpix = (newpix - threshold) / (1.0-threshold*1.1);
newpix.a = 1.0;
return vec4 (newpix);
}
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