Re: [Openexr-devel] CTL not working with exrdisplay

[Florian Kainz]

Hi Brendan,

your command line should either read

    exrdisplay -C transform_RRT -C transform_display_video GoldenGate.exr

or just

    exrdisplay GoldenGate.exr

In the second case the default transforms, transform_RRT and
transform_display_video, will automatically be applied.

The transform_RRT relies on transform_display_video to produce
the pixels that will actually be displayed.  Without the second
transform the output of transform_RRT will be discarded.  In this
case exrdisplay shows you the original image because it is re-using
a buffer that initially contained the original image from the file.
The buffer should get overwritten by the CTL transforms.  I guess
it would be better to display a black image if the CTL transforms
fail to produce any output.

The effect of the CTL transforms on the GoldenGate.exr image are
rather subtle; to get a more obvious effect, save the following CTL
program in file foo.ctl:

    void
    foo (output varying half displayR,
         output varying half displayG,
         output varying half displayB,
         varying half R,
         varying half G,
         varying half B)
    {
        displayR = B;
        displayG = R;
        displayB = G;
    }

Then run

    exrdisplay -C foo GoldenGate.exr

This should swap the R, G and B channels of the image.  You should
get a red sky and greenish city lights.

Florian



Brendan Bolles wrote:
> Hey all, has anyone gotten CTL working with exrdisplay?  I'm working  in 
> OS X (Xcode) and have gotten it all compiled and running with CTL  
> included and turned on.  Marching through the debugger, I can see  that 
> the .ctl file is being found and it looks like transforms are  being 
> applied.  But the view on screen never looks any different -  nearly the 
> same as when you use no CTL at all (with the -T flag).   I've been 
> testing with the two included files that seem to work,  
> transform_RRT.ctl and transform_EXR_DPX.ctl, but nothing happens with  
> either of them.
>
> It gets pretty confusing down deep in all that C++.  Is there  anything 
> I can look for that would verify that nothing is actually  happening and 
> try to maybe figure out why?
>
> I'm using all the latest stuff.  Everything appears normal  otherwise.  
> Here's what I've got in my shell:
>
>
> [fnord:mac/build/Release] mrb% ./exrdisplay -C transform_RRT ~/ 
> Development/sample_images/openexr-images-1.5.0/Tiles/GoldenGate.exr
> Warning: Environment variable CTL_DISPLAY_CHROMATICITIES is not set;  
> using default value (chromaticities according to Rec. ITU-R BT.709).
> Warning: Environment variable CTL_DISPLAY_WHITE_LUMINANCE  is is not  
> set; using default value (120 candelas per square meter).
> Warning: Environment variable CTL_DISPLAY_SURROUND_LUMINANCE  is is  not 
> set; using default value (12 candelas per square meter).
> Warning: Environment variable EXR_DISPLAY_VIDEO_GAMMA is not set;  using 
> default value (2.2).
> [fnord:mac/build/Release] mrb%
>
>
> Brendan
>
>
>
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