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Re: maintaining alpha value for intersecting lines?
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Re: maintaining alpha value for intersecting lines?


  • Subject: Re: maintaining alpha value for intersecting lines?
  • From: Alex Zavatone <email@hidden>
  • Date: Thu, 13 Sep 2012 10:46:31 -0400

It is higher.  That's what happens when the lines intersect.  The effect is additive.  Unless you have a mode setting where the compositing replaces what's below it.

The alpha of the top curve doesn't change at the intersection point.  What you're doing is putting one alpha-ed pixel on top of another, and the alpha on the top one lets the one below it show through based on the alpha value of the top pixel.



On Sep 13, 2012, at 8:43 AM, Koen van der Drift wrote:

> Just to clarify, I set the color of the path as follows:
>
> [[NSColor colorWithCalibratedRed: 0.1 green: 0.1 blue: 0.1 alpha:
> 0.5] setStroke];
>
>
>
> On Thu, Sep 13, 2012 at 8:40 AM, Koen van der Drift
> <email@hidden> wrote:
>> When I draw two lines using NSBezierPaths, both of which have an alpha
>> value of let's say 0.5, the alpha value appears to be higher at the
>> intersection (the color becomes more opaque). Is there a way to
>> maintain the original alpha value for lines that intersect?
>>
>> - Koen.
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References: 
 >maintaining alpha value for intersecting lines? (From: Koen van der Drift <email@hidden>)
 >Re: maintaining alpha value for intersecting lines? (From: Koen van der Drift <email@hidden>)

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