Add support for metadata in PNG/APNG images

[Euphoria]

As PNG pretty much the most used lossless image format these days, so is the importance and usage of PNG Metadata has grown.
Please add support for viewing, editing, and saving PNG Metadata. Included is an example image containing metadata critical to the context of the image.

02852-20230129221459-Heun-step_45-2324588829.png

[xnview]

sorry but there is no EXIF/XMP/IPTC metadata in this file

[WinnieW]

PNG format use a native metadata format, there are called metadata chunks.

http://www.libpng.org/pub/png/spec/1.2/PNG-Chunks.html

The PNG in the first post has metadata specified as tEXT chunk

[pitti911]

This issue is related to

viewtopic.php?f=82&t=42770&p=174462&hilit=chunk#p174462

as well. Also, the properties window in the browser is already able to display the mentioned data. That points to some kind of (rudimentary) capabilities in that direction already.

Also worth mentioning: The above image is made with stable diffusion, so while this chunk seems to have an internal structure that's going to be different depending on the actual content of the text chunk.

With that in mind, some basic parsing/scripting capabilites would be nice for View/fullscreen mode information overlay.

[crowley]

Hi,
Is it possible to add a function to edit these PNG metadata "Chunks"? It would be quite useful to be able to edit this via the properties panel that already shows the metadata.
My current workflow for editing the metadata is via python which is a tad more cumbersome

[XnTriq]

I did a few tests and posted the results.
XnView MP was the only program capable of saving metadata as eXIf chunk

While the PNG specification does not explicitly include a standard for embedding Exif image data from sources such as digital cameras, the preferred method for embedding EXIF data in a PNG is to use the non-critical ancillary chunk label eXIf.

Related: EXIF support in PNG