failure reading grib files with png compression

[robertwagner]

‘Data Representation Template 5.41 (Grid Point Data - PNG Compression)’

1) The Makefile for the grib format data (gdal-<version>/frmts/grib/GNUmakefile) DOES NOT check for

nor include the proper PNG settings and does not build the png wrapper code in the g2clib module (gdal-<version>/frmts/grib/degrib18/g2clib-1.0.4/{ dec_png.c, enc_png.c, pngpack.c, pngunpack.c } ).

2) Starting with RHEL 6.x attempted compiles of dec_png.c & enc_png.c fail with the error “undefined reference ‘voidp’”

Note: The dec_png.c and enc_png.c is not the latest version of the 3rd party library in gdal-1.11.0. The latest version has the voidp issue fixed. If you would like the patch form gdal-1.11.0 I can provide it.

[Kyle Shannon]

Can you provide the patch please?

[robertwagner]

Patch file

[robertwagner]

Replying to kyle:

Can you provide the patch please?

I just added it to the ticket.

[Jukka Rahkonen]

Great opportunity for someone to review the patch which is not big at all, accept or improve it, apply and make GDAL a bit better. Plus close the ticket and make the list of open issues shorter.

[Even Rouault]

kyle, do you still want to handle this ? Windows makefile would need an update too. A test file in the testsuite would be a plus too.

[Even Rouault]

In 35760:

GRIB: PNG decoder. Fix compiler warnings, undefined behaviour, and optimizations. Mixes of patch by zflamig ​https://github.com/OSGeo/gdal/pull/160 + fixes #5661 by robertwagner + securing dec_png() by myself)

[Even Rouault]

Related commits: r35758 + r35759