[Openexr-devel] Tiled Exr question re: dataWindowForLevel

[Jeremy Selan]

Hello!

We've been playing around with exr mipmap tiling recently, and I'm a bit 
surprised on how dataWindowForLevel behaves.

If my test is accurate (and it may not be)...

Say you have a 2K element:
displayRect (0,0) - (2047,1555)
dataRect (768,532) - (1342,1140)

if you use exrmaketiled to make a tiled version
exrmaketiled -m -t 128 128 original.exr mipmap.exr

Reading the levels back,   (using header.displayWindow(),  
sourceFile.dataWindowForLevel(lx, ly) )

level 0 looks good:
displayRect (0,0) - (2047,1555)
dataRect (768,532) - (1342,1140)

however, level 1 is quite surprising:
(768,532) - (1055,836)

The width and height appear to be correct, (1342-768)*0.5 = 1055-768

However, the origin for level 1 (and in fact all subsequent levels) is 
the same as for level 0. (see openexr-1.6.1/IlmImf/ImfTiledMisc.cpp : 77)

Is this expected?

My intuition would have been that the dataWindows's origin would scale 
with the width. I.e, this image should read:
(384, 266) - (958,570)

I can always work around this, but I just wanted to get some expert options.

Thanks!

-- Jeremy Selan