Re: [Openexr-devel] Y RY BY images

[Jim Hourihan]

On Mar 14, 2007, at 3:51 PM, Florian Kainz wrote:

> If you are using class RgbaInputFile to read the file, then the
> RY and BY channel names are special; RgbaInputFile assumes that
> they are sub-sampled with x and y sampling rates of 2.  When you
> use class RgbaOutputFile to write a Y/RY/BY image, then the RY
> and BY channels will automatically be sub-sampled.

I should have included more info. I'm using Imf::OutputFile to write.
I'm using Imf::InputFile to read (but this is clearly not an issue  
because
I can read Rec709_YC.exr and XYZ_YC.exr no problem).

> A Y/RY/BY image with without sub-sampling can be read via the
> general (arbitrary set of channels) interface, but RgbaInputFile
> will reject it.  Maybe this should be fixed; the changes in class
> RgbaInputFile would be manageable.  On the other hand, why would
> you want to write Y/RY/BY images without sub-sampling?  You might
> as well write RGB files.

I want the data sub-sampled, but Imf was core dumping on me. However,  
I didn't
realize it would do the sampling for me. Is there a way to prevent that?
I already have the data sub-sampled in separate planes (as a result  
of using
InputFile). My application caches the sub-sampled data for display.

I'll try handing it data that's not sub-sampled.

        -Jim