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CLOSED  Bug report #375  -  Gradients with transparency doesn't render the same in Cairo
Posted Apr 07, 2013 - updated Jan 05, 2019
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0
Votes
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icon_info.png This issue has been closed with status "Closed" and resolution "WON'T FIX".
Issue details
  • Type of issue
    Bug report
  • Status
     
    		 Closed
  • Assigned to
    Carlos López
  • Progress
       
  • Type of bug
    Not triaged
  • Likelihood
    Not triaged
  • Effect
    Not triaged
  • Posted by
    Carlos López
  • Owned by
    Not owned by anyone
  • Category
    Rendering
  • Resolution
    WON'T FIX
  • Priority
    Must fix before next release
  • Targetted for
    icon_milestones.png 0.64.1
  • Tags
    icon_customdatatype.png cairo gradient transparent
  • Difficulty
    icon_customdatatype.png Not determined
Issue description
When creating a gradient layer with one of the colors to be transparent, the interpolated color behaves different in Cairo than in Software.

See it here:

Software: https://www.dropbox.com/s/msbqp6beyf1cf18/Gradient-software.png

Cairo: https://www.dropbox.com/s/t2np871jkr0fuah/Gradient-cairo.png

And the file to render the example: http://dl.dropbox.com/u/7125719/Gradient.sifz
Steps to reproduce this issue
Create a gradient from (0,0,0,0) to (1,1,1,1) and composite it over a black solid color. Change between Cairo and Software render to see the difference.

#7
Comment posted by
Carlos López
May 21, 09:56
Seems that the interpolation of a gradient in Synfig is related to the used gamma. It need further research on how gradients work on Synfig. Possibly this bug won't fix since I can't modify the way that Cairo (pixman libraries) renders the gradient transition.
#8
Comment posted by
Carlos López
Aug 23, 17:35
In Cairo, Gradients are handled by pixman libraries. Synfig handles the color in its special way so it won't never look the same with transparency.