[vtk-developers] PNGWriter now writing out a black background after 17 Oct.

[Ken Martin]

That example is reading RGBA from a buffer that you have not set to have
alpha bitplanes. I do not know what OpenGL does in that case. Maybe the
resulting alpha is undefined. There are a few options here

1) set alpha bitplanes to 8 so that you get alpha

2) see if this is a regression related to VTK and try to find and fix it

3) wait until I revamp the window code on Linux at which point I will be
forcing all windows to have alpha bitplanes. From what I understand RGB
buffers (3 byte alignment) do not really make sense these days and we
should not be using them. They are a legacy from when raster memory was so
limited that saving the alpha bit planes was a big deal.

4) just change the default alpha bitplanes value to  in VTK right now
instead of waiting for the windowing cleanup




On Wed, Nov 9, 2016 at 5:18 PM, Andrew Maclean <andrew.amaclean at gmail.com>
wrote:

> Hi Guys,
>    For me this still appears to be the case. Try running the attached test
> code.
> In Windows and Linux, TestWIFPNGRGB.png are the same.
> In Windows TestWIFPNGRGBA.png has a transparent background, whilst in
> KUbuntu no image is produced just a transparent background.
>   Are you able to replicate this behaviour?
>
> Andrew
>
> On Wed, Nov 9, 2016 at 10:22 PM, David E DeMarle <dave.demarle at kitware.com
> > wrote:
>
>> Andrew, does this still appear to be the case in the 7.1 release branch?
>> If so mind filing a quick issue on gitlab with the 7.1 milestone tag?
>>
>
>
>
> --
> ___________________________________________
> Andrew J. P. Maclean
>
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-- 
Ken Martin PhD
Chairman & CFO
Kitware Inc.
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