How do I go about editing the metadata of a PNG file?

Question

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

Thanks in advance.

Answer 1

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.

Answer 2

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.

Answer 3

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.

Answer 4

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

Answer 5

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