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See http://www.libpng.org/pub/png/spec/1.2/PNG-Chunks.html
for info on 'Textual information' chunks.
"text chunks" set by Imagemagick renders correctly.
Set them as follows:

mogrify -set Title "This is the title" file.png
mogrify -set Comment "This is the comment" file.png
mogrify -set Description "Test Description" file.png

NB! Chunks already set (by i.e. GIMP) will prevent Imagemagick
from re-adding them correctly.

Predefined iTXt, tEXt and zTXt chunks:

   Title            Short (one line) title or caption for image
   Author           Name of image's creator
   Description      Description of image (possibly long)
   Copyright        Copyright notice
   Creation Time    Time of original image creation
   Software         Software used to create the image
   Disclaimer       Legal disclaimer
   Warning          Warning of nature of content
   Source           Device used to create the image
   Comment          Miscellaneous comment; conversion from
                    GIF comment