Recent changes to bugs

#2 png->sng->png conversion modify the image

2016-01-11T22:10:03.950000Z

status: open --> closed
assigned_to: Eric S. Raymond
Group: -->

#4 SNG has problems with control chars in zTXt

2016-01-10T11:57:44.118000Z

Also note that the PNG ISO spec says the following on the content of tEXt and zTXt chunks (see http://www.libpng.org/pub/png/spec/iso/index-object.html#11tEXt): "Characters other than those defined in Latin-1 plus the linefeed character have no defined meaning in tEXt chunks." -- in particular, control characters have undefined meaning.

That said, I still think they should survive a sng roundtrip; I merely wanted to point out that by including them in the first place, you may already be making a mistake...

#2 png->sng->png conversion modify the image

2016-01-10T11:40:50.197000Z

To the best of my knowledge, this is now fixed in the repository (and will be fixed in sng 1.1.0)

#3 Generates unparseable .sng

2016-01-08T20:41:18.747000Z

status: open --> closed
assigned_to: Max Horn
Group: -->

#5 won't build with libpng 1.5

2016-01-08T20:37:14.535000Z

status: open --> closed

#5 won't build with libpng 1.5

2016-01-08T20:36:40.433000Z

assigned_to: Max Horn
Group: -->

#4 SNG has problems with control chars in zTXt

2013-08-08T16:58:01.292000Z

Hm, that png does not seem to contain any zTXt chunk (looking at the file with a hex editor seems to confirm that). And with sng 1.0.5 it seems to survive the roundtrip just fine.

#3 Generates unparseable .sng

2013-08-08T16:50:38.303000Z

This is fixed in my sng fork, see https://github.com/fingolfin/sng/tree/modern-libpng

#5 won't build with libpng 1.5

2013-08-08T16:40:02.341000Z

I made a version of sng that works with current libpng, you can find its code here: https://github.com/fingolfin/sng

I also emailed esr about it, so perhaps this can be integrated into sng soon.

won't build with libpng 1.5

2013-08-06T05:21:50.242000Z

Compilation of sng currently fails in Cygwin, with multiple errors like this:

/cygdrive/c/Users/andrex/Home/dev/cygwin/sng/sng-1.0.5-1/src/sng-1.0.5/sngc.c:545:23: error: dereferencing pointer to incomplete type
  if (width != info_ptr->width && height != info_ptr->height)
                       ^

and

/cygdrive/c/Users/andrex/Home/dev/cygwin/sng/sng-1.0.5-1/src/sng-1.0.5/sngd.c:953:38: error: ‘PNG_HAVE_IDAT’ undeclared (first use in this function)
  if (after_idat != !!(up->location & PNG_HAVE_IDAT))
                                      ^

These appear to be caused by dependencies on libpng 1.2, which seems to be deprecated. Anyway libpng 1.2 is no longer available in Cygwin, so sng will no longer build there.