clean up the error-handling slightly. no magic numbers!
clean up the error-handling slightly. no magic numbers!


fengzhyuan/visionworkbench,DougFirErickson/visionworkbench,DougFirErickson/visionworkbench,AveRapina/visionworkbench,AveRapina/visionworkbench,AveRapina/visionworkbench,fengzhyuan/visionworkbench,AveRapina/visionworkbench,fengzhyuan/visionworkbench,AveRapina/visionworkbench,DougFirErickson/visionworkbench,AveRapina/visionworkbench,DougFirErickson/visionworkbench,fengzhyuan/visionworkbench,fengzhyuan/visionworkbench,fengzhyuan/visionworkbench,DougFirErickson/visionworkbench,DougFirErickson/visionworkbench,fengzhyuan/visionworkbench