aleph_knull's profile - activity

OpenCV with OpenEXR 2.2 (not with OpenEXR 1.7, which OpenCV defaults to) -- from source. I'll be building it on OSX and Linux.

Assuming the image data is pristine and processed properly, your OpenEXR image is expected to be in "scene_referred_linar" space -- i.e. it's got a gamma encoding of 1.0. In an OpenEXR image is a high dynamic range image that stores much more information than a normal monitor can display -- in some cases, over 30 stops of information are captured -- that's a huge exposure range! The values between 0-1 represent 0-255 in an 8 bit image. The values 0-13.5 roughly represent the range of a CINEON (log encoded 0-1024) image. Grabbing the min and max won't result in the intended image reproduction.

Depending on your viewing device, you need to apply a proper tonal curve to the EXR image for it to be faithfully reproduced on your monitor.

Likely you're on a "Rec.709" device so a gamma 2.4 should give you a very quick ballpark preview; on an sRGB monitor, a gamma 2.2 should provide a decent preview. While there are exact tonal curves defined for given display specifications, I figured you were looking for the quick solve without getting into actual sRGB and bt1886 tonal curve equations.

Hope this helps! JP

Hello -- can anyone help with compiling OpenCV against OpenEXR2.2.0?

In the git repo 3.2.0 branch, I've tried replacing everything in ./opencv/3rdparty/openexr/ with corresponding 2.2 libs as well as updating the "version string" and "package_string" in IlmBaseConfig.h.cmakein and OpenEXRConfig.h.cmakein to 2.2.0 from 1.7.0

I should also mention that I do have OpenEXR2.2.0 fully installed and working on my OSX machine. I don't use any package managers such as homebrew, or fink, or macports; I do 100% BSD style installs from source.

I'm able to get opencv to install no problem; it's just compiling it against ilmbase/OpenEXR 2.2.0 that I'd love to get sorted!

Thanks in advance! JP