Re: [Groff] Using pic/groff/gs to produce gif/jpeg

[Larry McVoy]

I've never found a good way to script this.  The process I use is to 
open the postscript file with gimp, crop and save.  It would be very
pleasant to have a way to quickly generate high quality cropped 
images from groff.  If anyone knows how to do that I'd like to 
know too.

On Wed, May 11, 2005 at 02:08:50PM +0100, David Griffiths wrote:
> Hi, I'm new to pic/groff and I've been having some problems producing 
> either gif or jpeg images using them. The basic problem seems to be that 
> pic/groff/postscript all have the concept of a page that they are 
> drawing on whereas I want the resulting image to have all the whitespace 
> cropped from the margins. This is to go in a web page so the idea of a 
> page doesn't make sense.
> 
> Anyway I started out following some instructions here: 
> http://www.spinellis.gr/sw/umlgraph/doc/faq.html#antialias but the 
> resulting command was very slow. Here are my findings as pasted from my 
> internal blog. I wondered if they made sense or if I'm missing some 
> simpler approach to the whole thing (btw I need the gs stage because 
> using -T gif in groff produces very poor text, no antialiasing).
> 
> Thanks!
> 
> Dave
> 
> From my blog:
> 
>  I missed the hint in the FAQ and after a bit of messing around got the 
> following command to work:
> 
> pic test | groff | ps2eps | gs -dDEVICEHEIGHTPOINTS=1000 -q -r360 
> -dNOPAUSE -sDEVICE=pnm -sOutputFile=- - -c quit | pnmcrop | pnmscale 0.5 
> | ppmtogif > test.gif
> 
> I had to add the -dDEVICEHEIGHTPOINTS=1000 option because without that 
> it chopped off the top of the picture.
> 
> Anyway, I think I prefer this approach if only because the pnmscale 
> command gives me the option to scale the size of the image. Plus 
> ppmtogif gives me control over transparency.
> 
> Posted by D. H. Griffiths on May 04, 2005 at 07:02 AM EDT
> I've been playing around with this some more because the command above 
> was just so slow (eg 17 seconds on my T40 for a trivial diagram). Turns 
> out that most of that time is spent in pnmcrop. The image is far larger 
> than it needs to be (as specified by the resolution argument -r360) and 
> is then shrunk back down again with pnmscale (for my tests I'm using 
> pnmscale 0.25). Why is that? Well if you use -r90 and get rid of the 
> pnmscale, the text looks ragged as though it's missing antialiasing. But 
> I found that you could overcome that by specifying -dTextAlphaBits=4 in 
> the gs command. So you end up with a command like this:
> 
>     pic test | groff | ps2eps -q | gs -dTextAlphaBits=4 
> -dDEVICEHEIGHTPOINTS=1000 -q -r90 -dNOPAUSE -sDEVICE=pnm -sOutputFile=- 
> - -c quit | pnmcrop | ppmtogif > test.gif
> 
> now that's about four times faster because the intermediate pnm image is 
> four times smaller. This command took about 4 seconds on my Thinkpad. 
> But I found a still faster way.
> 
> Why bother to go to pnm format in the first place, why can't the image 
> be created directly by ghostscript? Well the answer is that can, but 
> ghostscript can only produce jpeg images, not gif. Which is fine for me. 
> The next issue relates to the pnmcrop command. What that does is chop 
> blank space from around your image. The problem is that a lot of what 
> groff and postscript do revolves round the concept of writing to a page 
> (typically letter size). Pic for instance has its coordinate origin at 
> the bottom left but positions your image at the top of the page. If you 
> play around you run into all sorts of issues with the image having white 
> space above or below or the image top gets chopped off because it's 
> above the top of the imaginary page and so on. After a lot of messing 
> around I came up with this version of the command:
> 
>     pic test | groff | ps2eps -q -g | fixbox | gs -dTextAlphaBits=4 -q 
> -r90 -dNOPAUSE -sDEVICE=jpeg -sOutputFile=- - -c quit > test.jpg
> 
> the -g option to ps2eps is important because that tells it to use the 
> "internal bbox device of ghostscript" (whatever that means!), but anyway 
> it prevents ps2eps from setting the top of the bounding box to the top 
> of the default page. It's important because without it the diagram goes 
> above the bounding box set by ps2eps and the image gets cropped.
> 
> fixbox is a small python script I wrote that is a much simplified 
> version of epstopdf. What this does is to move the image to the bottom 
> left corner and set the page size to just include the bounding box. 
> Using this means that there is no longer a need for cropping. The script 
> is here:
> 
> #!/usr/bin/python
> # This script converts the BoundingBox of a postscript file so that the 
> origin is at
> # the bottom left corner (0, 0). It also sets the pagesize which avoids 
> the need for
> # cropping blank space from the image.
> 
> import sys
> import os
> import re
> 
> inlines = sys.stdin.readlines()
> 
> for line in inlines:
>     if line.find("%%BoundingBox: ") != -1:
>         tokens = line.split()
>         minx = int(tokens[1])
>         miny = int(tokens[2])
>         maxx = int(tokens[3])
>         maxy = int(tokens[4])
>         new_maxx = maxx - minx
>         new_maxy = maxy - miny
>         print "%%BoundingBox: 0 0 " + str(new_maxx) + " " + str(new_maxy)
>         print "<< /PageSize [" + str(new_maxx + 10) + " " + 
> str(new_maxy + 10) + "] >> setpagedevice"
>         print "gsave -" + str(minx) + " -" + str(miny - 1) + " translate"
>     else:
>         print line,
> 
> print "grestore"
> 
> And finally, the best news is that this takes just 1 second to run!
> 
> 
> 
> _______________________________________________
> Groff mailing list
> address@hidden
> http://lists.gnu.org/mailman/listinfo/groff

-- 
---
Larry McVoy                lm at bitmover.com           http://www.bitkeeper.com