Regarding this correction:
Fix Unpaper issue due to an unexisting variable gb#668027 There was a temporary_dir varibale that was left unchanged when the configuration started using TEMPORARY_FOLDER. Thanks to Buganini Q for reporting and posting the fix.

It would not be good to test the error return in callback routine, like it is done for deskew and return if set? I did not see if it is processed by callers returned, when debugging for rediscovering this bug. If not, printing a message, would speed pinpoint errors in unpaper, like conversion errors.

For instance, upon instrumenting, I found a situation that the conversion of PNG 8bit to PBM fails in unpaperImage:

imagePreprocessingFinishdedCb
cannot write mode LA as PPM

Without the error processing, it will trigger the same error message.

Any way, congratulations for the great work.

http://download.opensuse.org/repositories/home:/jsuarezr:/OCRFeeder/