Exiftool and PNG

[Archive]

[Originally posted by linuxuser on 2005-05-31 13:25:21-07]

Is there a special reason, why exiftool doesn't support PNG-files? PNG-files can contain some exif-fields and it would be nice to read and change these with exiftool.

[Archive]

[Originally posted by exiftool on 2005-05-31 15:16:12-07]

I haven't had a request yet for PNG support.  Plus, I have looked for PNG documentation and haven't found anything that was very readable.  I'll add this to the to-do list if PNG support would be useful to you.

[Archive]

[Originally posted by linuxuser on 2005-05-31 16:02:11-07]

That's very nice, that you pick up my suggestion. AFAIK png supports exif only _partially_

http://download.mirror.ac.uk/sites/www.libpng.org/pub/png/spec/1.2/PNG-Chunks.html#C.Anc-text is invalid unfortunately. I am busy at the moment, so I cannot search for this document. AFAIR this paper discussed problems with exif and png.

I will tell you, why I like png. IMO it produces the smallest lossless filesizes. I do something like this:

convert -quality 95

Please note, there is NO -quality 100, like with jpeg. 9 means the highest compression and 5 the compression type. Unfortunately the ImageMagick manpage doesn't say a lot to this topic. But if I use convert, some exif-data is kept.

Please be patient for answers to my other postings

It you see this without linebreaks, I have no idea why. The preview doesn't show it, also I typed it with the newest Firefox. But it worked with other postings.