[Reproducible-builds] Best approach to strip timestamp in postscript files

[Dhole]

Hi Alexis,

On 16-03-31 16:51:43, Alexis Bienvenüe wrote:

> 0) patch the kannel package to remove these tags from the PS files
> after
> PNG->PS conversion with a perl line (I made this in [1]).
> 
> 1) patch the 'convert' code to remove CreationDate tags from PS
> output.
> But maybe some code somewhere relies on this tag to work?
> 
> 2) add an option to the convert command to remove CreationDate tags
> from
> PS output, and add this option to the 'convert' calls in kannel build.
> 
> 3) adds some code to strip-nondeterminism to remove all lines starting
> from "%%CreationDate:" from PS files
> 
> Note that 1) and 2) may require to do the same for graphicsmagick, as
> imagemagick can be replaced by graphicsmagick-imagemagick-compat?
> 
> Could you tell me if you think it could be helpful if I work on one of
> these approaches? Or maybe some current work is already going to solve
> this issue?

I believe the best option would be to make 'convert' honour the
environment variable SOURCE_DATE_EPOCH [1] when defined, when embedding
the CreationDate tag.  That's the aproach we have been taking when
removing the timestamp (as proposed in your point 1) could break other
packages depending on that tag.  Also, consider that this approach is
more general (and thus benefits more packages) than point 0, and also
needs less manual intervention than point 2 (because the
SOURCE_DATE_EPOCH variable can be defined during the build process as a
general procedure of the building environment, and so you don't need to
modify any build process of packages that use 'convert').

And I think it would be very helpful if you work on that :) (and also in
implementing SOURCE_DATE_EPOCH in graphicsmagick if there is the same
issue there).

[1] https://wiki.debian.org/ReproducibleBuilds/TimestampsProposal

Cheers,
-- 
Dhole
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