Alley in Pisa, Italy

by Lars Kotthoff

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How do I go about editing the metadata of a PNG file? Is there some free software I can use?

Thanks in advance.

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Surprisingly, this seems like a hard thing to do. While a quick search turned up a few non-free programs that claimed to be able to edit PNG metadata, the only free options I found were for command line programs; not the easiest things to use. blog.client9.com/2007/08/… –  Sean Oct 2 '10 at 21:23
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What operating system(s) are you interested in doing this on? –  Rowland Shaw Oct 3 '10 at 9:24
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Just a note: meta-data do not necessarily follow the file if manipulated in other programs. The reason for this is that programs are free to support or ignore any additional chunks in the file besides the image descriptor and data itself. This means the program can "forget" the unsupported (by the program) chunks when re-saving the file back to disk. Properly written programs will "remember" those chunks and save them along. I just mention this as someone said that data doesn't always stick - this is the main reason in addition to software that removes these on purpose to reduce file-size. –  Ken Fyrstenberg Dec 14 '12 at 19:18

5 Answers 5

From the Wikipedia page for 'pngcrush',

The main purpose of pngcrush is to reduce the size of the PNG IDAT datastream by trying various combinations of compression methods and delta filters. However, pngcrush can also be used for various manipulations of PNG images, such as changing the bit depth, removing unwanted ancillary chunks, or adding certain chunks including gAMA, tRNS, iCCP, and textual chunks.

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For the MAC OSX, there is a freeware called 'PNGCommentator'.
Have not seen it on other platforms.

PNG metadata can now be added and edited at the click of a mouse. Version 1.2 adds support for batch processing and customisable presets, allowing for much faster workflows. Text macros extend this even further, allowing the software to automatically insert data such as the date or filename.

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MetadataTouch can edit PNG metadata, but it is not free.

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If metadata is added to PNG files, such as keywords, it doesn't "stick" permanently. I found the only safe way was to use Bridge > Photoshop > Image processor and batch change the PNG to a JPEG, PSD, or TIFF file. I used tiff LZW to save space and even then it is a larger file than the png. I needed this to be able to add keywords and descriptions to pngs in scrapbook kits.

This was not my idea completely. I was changing the file extension in a more round about way and found this presented by a scrapbooker whose name and site I forget. I think her first name was Kayla.

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This? digiscrap101.com/2011/03/… –  mattdm Dec 30 '11 at 1:24
    
I may be misreading it, but it sounds to me that @liz is not adding metadata to the PNG files at all. Rather converting to some other format that handles meta data better, and using that. Is this what you are really doing? –  Pat Farrell Dec 13 '12 at 4:01

TweakPNG is a free sorftware that can edit PNG metadata (Windows only).

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