+ elsif ($fn =~ m/\.png/i) { $cmd = "pngtopnm < \"$fn\""; }
+ elsif ($fn =~ m/\.xpm/i) { $cmd = "xpmtoppm < \"$fn\""; }
+ elsif ($fn =~ m/\.bmp/i) { $cmd = "bmptoppm < \"$fn\""; }
+ elsif ($fn =~ m/\.tiff?/i) { $cmd = "tifftopnm < \"$fn\""; }
+ elsif ($fn =~ m/\.p[bgp]m/i) { return `cat \"$fn\"`; }