CALayer compositingFilter trouble
CALayer compositingFilter trouble
- Subject: CALayer compositingFilter trouble
- From: Markus Spoettl <email@hidden>
- Date: Thu, 26 Apr 2012 18:12:37 +0200
Hello,
I'm posting this here because quartz-dev seems dead. I have a layer
hosting view where I use a -compositingFilter with a CIColorBlendMode
filter (default settings). It's constructed and applied to the layer
like this:
CIFilter *cf = [CIFilter filterWithName:@"CIColorBlendMode"];
[cf setDefaults];
[overlayLayer setCompositingFilter:cf];
overlayLayer is z-ordered above another layer that has a grayscale
content (a height field). I draw colors into the overlayLayer which in
turn colorizes the height field. Works fine but some colors give me
grieve in that the hue is completely wrong and I have no idea why.
To illustrate the problem I've uploaded an annotated screenshot here:
http://www.shiftoption.com/temp/blendingtrouble.png
It shows both the colors used (upper rect) and blended result (lower
rect). The upper screen shot is for two colors that "work". The lower is
for a color that doesn't (color C). The difference between the two is
saturation, 0.1 works, 0.003 doesn't (in case you wonder, 0.004 works).
So, these work:
[NSColor colorWithCalibratedHue:0.55 saturation:0.1 brightness:1.0
alpha:1.0]
[NSColor colorWithCalibratedHue:1.0 saturation:0.8 brightness:0.8 alpha:1.0]
This one doesn't:
[NSColor colorWithCalibratedHue:0.55 saturation:0.003 brightness:1.0
alpha:1.0]
I don't have the slightest idea why the hue changes so dramatically.
Maybe this is to be expected? Why? Can I avoid that? How?
Any tips greatly appreciated!
Regards
Markus
--
__________________________________________
Markus Spoettl
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