Re: EXIF support in PNG

I pushed 'jpegtopng.cpp' to github:

https://github.com/jbowler/jpegtopng

It is an agnostic, minimal, program to convert a JPEG into a PNG.  The
program is currently 349 lines long, most of which is either
boilerplate or writing numbers.  The 'big' bits are the JPEG
decompression, which uses libjpeg and a loop over the scanliens, and
the PNG compression, which uses zlib and is the most complex part of
the code.

This is the *encoder* part of the equation; it does encode a PNG (it
works too).  It doesn't encode anything beyond the raw image data.

I believe I can patch this to preserve the EXIF APP1 marker from an
appropriate JPEG relatively easily, but I haven't done so yet.  I'm
going to use exif 0.6.21 for the other side, the much more critical
read side.  exif 0.6.21 is here:

https://sourceforge.net/projects/libexif/files/exif/0.6.21/

John Bowler

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