Re: [Groff] How to create updates for revised edition of book?

[Ralph Corderoy]

Hi Greg,

> That should be good, but the problem is that O'Reilly want only
> changed pages.

I thought at first that you meant they wanted you to make edits so the
page breaks occur in the same place in the text, i.e. you only change
page 3 and text doesn't flow off it onto page 4, etc.  Kernighan had to
do that for a re-print of _The Practice of Programming_, e.g. by
lengthening the area of the page used for the body text, and it was
causing some problems with one particular program listing.

> My current approach is pretty manual: I run diffs on the sources, find
> the corresponding pages in the PostScript output, and use Emacs to
> remove the rest.  I'm left with the feeling that there must be a
> better way.

How about using GhostScript to print each page to a PNM file, use
netpbm, e.g. pnmcut(1), to strip off the outside-print-area markup, and
then compare the images of each page from the before and after
`printouts'.  As long as the resolution is suitably high enough it
should catch small changes.

Basically the same as placing one piece of paper over the top of the
other and holding it up to the light.

Cheers,


Ralph.