2012 March 1
Yet another entry in a
long series of reference
posts about converting image formats. Sometimes you have a bitmap plot that
needs to be converted to EPS for submission to a journal. My go-to command is
convert foo.png foo.eps but this can give bad results.
For a large PNG file, the best approach using standard tools that I’ve discovered is to use the NetPBM programs:
pngtopnm figure.png |pnmtops -equalpixels -scale 0.24 -psfilter \ -flate -noturn -ascii85 -nocenter - >figure.eps
Annoyingly all of these options seem to be necessary to give useful output. The scale factor is the number of inches per 72 pixels; 0.24 gives you about 300 DPI.
pnmtops documentation says that the
-flate option (which turns on
compression and can be a huge deal for large images) sometimes produces busted
output. There’s also an
-rle option that will be less efficient (especially
for bitmaps that don’t contain long stretches of single colors). The
documentation also references a program called
bmeps that is claimed to do a
better job of this kind of conversion. The same seems to be said of
sam2p, but one of the benefits of the
above command is that the NetPBM tools are installed on most Linux machines.
When all of these options are working, I can generate a good EPS that’s only 15% larger (on-disk) than the original PNG, which is pretty cool.
Earlier: A Fancier Galactic Center Map
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