$ pamgauss 3 3 -sigma=.5 -tupletype=GRAYSCALE >gauss.pam $ pnmconvol -nooffset gauss.pam tmp > /dev/null pnmconvol: WARNING - this convolution matrix is biased. average weight = -7.007843 (unbiased would be 1) pnmconvol: Maybe you want the -nooffset option?
*** Bug 338236 has been marked as a duplicate of this bug. ***
added a fix from upstream to 10.51.00-r1 for the issue http://sources.gentoo.org/media-libs/netpbm/files/netpbm-10.51.00-pnmconvol-nooffset.patch?rev=1.1