Hi,
this is annoying: I'm trying to create a variable blur CIFilter effect where
the mix between blurred and unblurred image is determined by the values stored
in the Blue channel of the input image. It works OK on a completely opaque
image, but not on one with a transparent background. In this case, I end up
with a dark line around the border between opaque areas.
Here's the CIFilter kernel routine:
kernel vec4 TexCntrlBlur(sampler Image, float Blur, float Bal)
{
vec2 xy = samplerCoord(Image);
vec4 unblurred = (sample(Image, samplerCoord(Image)));
vec4 blurred = unblurred;
float ctrl = unblurred.b;
const vec2 offsets_0 = vec2(0.0);
const vec2 offsets_1 = vec2(-0.75) * samplerSize(Image);
const vec2 offsets_2 = vec2(-1.0, 0.0) * samplerSize(Image);
const vec2 offsets_3 = vec2(-0.75, 0.75) * samplerSize(Image);
const vec2 offsets_4 = vec2(0.0, -1.0) * samplerSize(Image);
const vec2 offsets_5 = vec2(0.0, 1.0) * samplerSize(Image);
const vec2 offsets_6 = vec2(0.75, -0.75) * samplerSize(Image);
const vec2 offsets_7 = vec2(1.0, 0.0) * samplerSize(Image);
const vec2 offsets_8 = vec2(0.75, 0.75) * samplerSize(Image);
const vec2 offsets_9 = vec2(-1.6, 0.0) * samplerSize(Image);
const vec2 offsets_10 = vec2(1.6, 0.0) * samplerSize(Image);
const vec2 offsets_11 = vec2(0.0, -1.6) * samplerSize(Image);
const vec2 offsets_12 = vec2(0.0, 1.6) * samplerSize(Image);
const float weight_0 = 4.0;
const float weight_1 = 2.0;
const float weight_2 = 2.0;
const float weight_3 = 2.0;
const float weight_4 = 2.0;
const float weight_5 = 2.0;
const float weight_6 = 2.0;
const float weight_7 = 2.0;
const float weight_8 = 2.0;
const float weight_9 = 1.0;
const float weight_10 = 1.0;
const float weight_11 = 1.0;
const float weight_12 = 1.0;
blurred = vec4(0.0);
blurred += (sample(Image, xy + offsets_0 * Blur)) * weight_0 / 21.0;
blurred += (sample(Image, xy + offsets_1 * Blur)) * weight_1 / 21.0;
blurred += (sample(Image, xy + offsets_2 * Blur)) * weight_2 / 21.0;
blurred += (sample(Image, xy + offsets_3 * Blur)) * weight_3 / 21.0;
blurred += (sample(Image, xy + offsets_4 * Blur)) * weight_4 / 21.0;
blurred += (sample(Image, xy + offsets_5 * Blur)) * weight_5 / 21.0;
blurred += (sample(Image, xy + offsets_6 * Blur)) * weight_6 / 21.0;
blurred += (sample(Image, xy + offsets_7 * Blur)) * weight_7 / 21.0;
blurred += (sample(Image, xy + offsets_8 * Blur)) * weight_8 / 21.0;
blurred += (sample(Image, xy + offsets_9 * Blur)) * weight_9 / 21.0;
blurred += (sample(Image, xy + offsets_10 * Blur)) * weight_10 / 21.0;
blurred += (sample(Image, xy + offsets_11 * Blur)) * weight_11 / 21.0;
blurred += (sample(Image, xy + offsets_12 * Blur)) * weight_12 / 21.0;
vec4 finalPix = mix(unblurred,blurred,1.0 - ctrl);
return vec4(finalPix.rgga);
}
Can anyone spot where I'm going wrong? It's probably got something to do with
pre or un-multiplying, but I can't seem to work out how to fix the problem.
Cheers,
a|x
http://machinesdontcare.wordpress.com
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