pstopng

Following this thread and my need to convert IDL .ps files to .pngs so that I can view them in Mac Preview without having to go through an (often failed) conversion process led to a few discoveries.

First, it is challenging to get ImageMagick's convert to make an opaque background for the .ps file without seriously degrading the resolution. This can be accomplished by passing both the -alpha Off and the -density 300 simultaneously. This is slow, though, and recommendations to speed it up using the -limit area 4096 -limit memory 4096 tags actually made it slower!

However, the thread pointed out that ghostscript can do the conversion directly:
gs -dBATCH -sDEVICE=png16m -r300 -dEPSCrop -dNOPAUSE -sOutputFile=XXX.png XXX.ps

-sDEVICE sets the output to png, -r300 tag sets the density to be 300 pixels/inch, -dEPSCrop is necessary to get the right sized image out (otherwise it defaults to a portrait 8.5x11), and -dBATCH prevents the gs command line from activating after the command is executed. I'm not sure if -dNOPAUSE is necessary, but apparently if you don't activate it you have to do something after every page is processed.

My code to do batch ps-to-png conversion is available at http://code.google.com/p/agpy/source/browse/trunk/agpy/pstopng.

Timing demonstrations (units are seconds, R is 'real' or clock time, 'U' is user time, and 'S' is system time):

/usr/local/bin/convert -density 300 -alpha Off deline_zero_10hz_timestreams_003.ps deline_zero_10hz_timestreams_003.png
TIMING: R: 3.126 U: 2.948 S: 0.084
/usr/local/bin/convert -limit area 4096 -limit memory 4096 -density 300 -alpha Off deline_zero_10hz_timestreams_003.ps deline_zero_10hz_timestreams_003.png
TIMING: R: 3.800 U: 2.970 S: 0.161
gs -dBATCH -sDEVICE=png16m -r300 -dEPSCrop -dNOPAUSE -sOutputFile=deline_zero_10hz_timestreams_003.png deline_zero_10hz_timestreams_003.ps
TIMING: R: 0.801 U: 0.781 S: 0.017