Jess
With the threshold at .9, you only have 10% of the colour range, or 25
colours per channel if you're in 8bit colour. It's just not accurate
enough.
To get around it, you need 16bit colour. If the image is something
you're making inside QC then put all of this in a render in image and
set it to 16bit. That should make it smooth again. If you're loading a
picture you're stuck with the colour range in the file really.
Chris
On 16 Oct 2008, at 18:37, Jesse Lucas <[EMAIL PROTECTED]> wrote:
Thanks Chris,
But it looks like my code wasn't as bad as I thought. Yours works
fine too but I still have a problem:
On high level of the threshold (0.9 --> 1) I get like trace effect.
Similar to using an accumulator. The brightest part of the image
seems to become transparent and the pixels accumulate underneath.
Any idea why ?
Thanks
JeSs
Le 16 oct. 08 à 16:53, Chris Wood a écrit :
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 PROTECTED]>
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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