[Python-Dev] Add pure python PNG writer module to stdlib?

Brett Cannon brett at python.org
Sun Jun 11 01:35:10 CEST 2006

On 6/10/06, Johann C. Rocholl <johann at rocholl.net> wrote:
> I'm working on simple module to write PNG image files in pure python.
> Adding it to the standard library would be useful for people who want
> to create images on web server installations without gd and imlib, or
> on platforms where the netpbm tools are not easily available.
> Does anybody find this idea interesting?

Yes, although I wouldn't want an interface taking in strings but something
more like an iterator that returns each row which itself contains int
triples.  In other words more array-based than string based.

Does anybody think it could go into stdlib before the feature freeze for 2.5
> ?

Nope.  To get added to the stdlib there needs to be support from the
community that the module is useful and best-of-breed.  Try posting on
c.l.py and see if people pick it up and like it.  No way that is going to
happen before b1.  But there is always 2.6 .


The module consists of only one file. It imports only sys, zlib,
> struct (maybe re for testing).
> Some benchmarks for comparison with the pnmtopng program (from
> netpbm), encoding a plain RGB file with 24 bits per pixel, input file
> size 11520017 bytes (11M), measured with the 'time' command, including
> Python interpreter start-up:
>                         pnmtopng        png.py
> straight encoding       1.31 seconds    0.72 seconds
> resulting file size     342953 bytes    292885 bytes
> interlaced encoding     3.78 seconds    4.88 seconds
> resulting file size     422441 bytes    346872 bytes
> The source code of the module lives here:
> http://svn.browsershots.org/trunk/shotfactory/lib/image/png.py
> http://trac.browsershots.org/browser/trunk/shotfactory/lib/image/png.py
> I am willing to maintain the module for 5+ years, as it is a small but
> important part of my main project. I am also willing to write latex
> documentation and tests for the module, and I think I could do that
> within the next three days. The module is licensed under the Apache
> License 2.0, and I am ready to sign a contributor agreement for the
> PSF.
> I will probably add support for more different PNG formats, especially
> alpha channel transparency, and then maybe color palettes. I don't
> plan to add PNG decoding because it would make the module much larger
> and rather complex.
> Sorry if this contribution seems brash. Perhaps it is easy enough to
> download and deploy my module separately. But I thought that if there
> is a chance to get it in before beta1, I should not hesitate and just
> ask.
> Cheers,
> Johann
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