I still don't know how to set attribute in OpenEXR, its here in /usr/include/OpenEXR/ImfStandardAttributes.h // // dwaCompressionLevel -- sets the quality level for images compressed // with the DWAA or DWAB method. // IMF_STD_ATTRIBUTE_DEF (dwaCompressionLevel, DwaCompressionLevel, float) but c++/c still definitely not my language ... I killed few blank lines in fileexr.C, I hope this is ok Additions to asset.c | h not included ..They not really usable without setting this new attribute Also, I still have no idea how to downpropagate cpu count .. file.C knows it, but File::EXR not ...