Reading png text chunks

ROOT
1

Hi,

Is there an easy way to access png text chunks through TImage?

Thanks,
Vyacheslav

2

You mean retrieving a text string drawn in binary picture like a png file ?
No, this does not exist.

3

I’m guessing that Vyacheslav is asking if you can access the embedded text in a png file. I don’t know if or how to do it in Root, but I have an example script that both embeds text in png files and then extracts it:
www-cdf.fnal.gov/~cplager/latex/#png

Cheers,
Charles

4

Sorry, let me be more detailed.
I have an application that creates a TImage from a png buffer using
SetImageBuffer(&my_char_png_buffer)
There is some useful info contained in the zTXt chunk that i would also like to extract. It does not look to me at this point like it is possible without writing a custom png read function.

5

That is what I thought you meant. Looking at my script (linked above), it looks like:

pngtopnm -text output.txt myimage.png

extracts the text. Assuming you have pngtopnm on your system, you can run this from Root.

Cheers,
Charles