Store and retreive string in PNG

[G-e-n-e-v-e-n-s-i-S]

Is it possible to store some string data inside a wxImage, save it to disk as a PNG image, then later load it and retrieve the string?

I tried using wxImage::SetOption() and wxImage::GetOption() but these don't seem to persist upon writing to disk.

I also haven't found any function to access the iTXt, tEXt, or zTXt chunks.

I'm open to any kind of ugly/platform specific hack (except storing it in the filename).

Thanks!

[vadz]

No, wxImage doesn't provide support for working with PNG-specific chunks. In principle, it should be possible to handle this using the existing options mechanism by defining more PNG-specific options corresponding to such chunks, but it risks being really ugly. If you need full support of the PNG format, using libpng directly is probably a better idea.

[G-e-n-e-v-e-n-s-i-S]

I don't need full PNG support. I really just need the bare minimum functionality of storing a string inside the file when saving it on disk, and retrieving it on load.

I'm trying to avoid adding yet another library dependency to my project just for a single function. You're saying it can be done with Options in principle? Would I need to override the wxImage::SaveFile() function? I'm willing to give it a go if you can start me in the right direction.

Thanks for your reply.

[vadz]

You already have an implicit dependency on libpng, as it's used by wxImage, so using it shouldn't be a big change.

Anyhow, you can't do this outside of wx. What I meant by "it can be done with options in principle" is that it should be relatively simple to add some wxIMAGE_OPTION_PNG_tEXt and handle it in the code by loading it from/saving it to tEXt chunk. This still needs to actually be done.

[G-e-n-e-v-e-n-s-i-S]

Solved by #25565