routine. Note that it is not the "real" sharpen which should be built on top of a gaussian kernel. git-svn-id: file:///srv/caca.zoy.org/var/lib/svn/libpipi/trunk@2662 92316355-f0b4-4df1-b90c-862c8a59935f
git-svn-id: file:///srv/caca.zoy.org/var/lib/svn/libpipi/trunk@2659 92316355-f0b4-4df1-b90c-862c8a59935f
git-svn-id: file:///srv/caca.zoy.org/var/lib/svn/libpipi/trunk@2604 92316355-f0b4-4df1-b90c-862c8a59935f
git-svn-id: file:///srv/caca.zoy.org/var/lib/svn/libpipi/trunk@2262 92316355-f0b4-4df1-b90c-862c8a59935f