Add metadata information to a png file
lazarus / 39-Graphics

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dcelso · 2016-11-03 14:20

Helllo to all,
How can I add extra information to a png file?

I have tried use TPortableNetworkGraphic but I can not find any
property to add custom information.

Thanks.

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wp · 2016-11-03 14:26

The png file format does not support metadata
(https://stackoverflow.com/questions/8113314/does-png-support-
metadata-fields-like-author-camera-model-etc). You must use jpg or
tiff for this.

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dcelso · 2016-11-03 14:33

Are you sure?

https://en.wikipedia.org/wiki/Portable_Network_Graphics  <--- 
"Ancillary chunks" section

Have a nice day, bro.

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Thaddy · 2016-11-03 14:36

http://dev.exiv2.org/projects/exiv2/wiki/The_Metadata_in_PNG_files
https://en.wikipedia.org/wiki/Portable_Network_Graphics#Ancillary_chun
ks
https://www.w3.org/TR/PNG/#11textinfo

So png does support metadata. It just is not supported by the LCL
component atm.
I suggest you ask the maintainer to support it. Can be on the bug
tracker.

@wp SO is not always a good source of information. Look for the
specifications.....

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apeoperaio · 2020-11-12 11:14

I would like to know if metadata is now supported using
TPortableNetworkGraphic.

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wp · 2020-11-12 11:25

Certainly no.

I wrote an exif library (fpexif, https://sourceforge.net/p/lazarus-
ccr/svn/HEAD/tree/components/fpexif/), but it inspects only the jpeg
and tiff file formats, and I don't have time atm to extend it to png.

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apeoperaio · 2020-11-12 13:10

Thank you, I will look at it