Created attachment 212986 [details]
Screenshot of poor rendering
GwenView doesn't seem to be handling 10K .TIF files very well. Attached is a screenshot of the GwenView render of the 2nd thumbnail from the right. The original file is also included.
This doesn't have anything to do with the FreeBSD base system. Please file a bug against the corresponding port, if you suspect the problem is FreeBSD-specific, or against the upstream project.