Metadata in image files

Notes by Walter vom Saal. Updated 3/4/2011

I am not an expert on metadata in files, and this is mostly a note to myself on a problem I found trying to view metadata in some image files.

I was trying to explore what image filetypes contain metadata.

I used IrfanView to look at the metadata in some of my image files. IrfanView is a powerful free image viewer that is widely used and respected. You must download the program and also install the plugins to see file metadata. If you open a photo in IrfanView and click Image > Information and you can see IPTC fields, EXIF fields, and Comment fields in JPEG files.

I also tried to write and read metadata from the files using ThumbsPlus.

I didn't test everything, but I did find an interesting thing while using GIF files and PNG files. Irfanview shows no metadata on some GIF and PNG files I have. However, I can open them in ThumbsPlus, add or edit a comment (double-click to open the file in Thumbs, select Edit > Add Comments or Edit Comments), and resave the file, and if I so it seems to write it to the file. If I then open another instance of ThumbsPlus and use the same procedure I can see those comments on the file. The comments also copy to the ThumbsPlus annotation when I select Options > Preferences > Thumbnails > Automatically copy image comments to database annotations = always and regenerate the thumbnail with F3. So it seems like GIF and PNG files must allow metadata but IrfanView is not showing it.

I also tried this with BMP files but in that case no comment seemed to get written to the file.

Conclusion: IrfanView doesn't show metadata for all file types. It shows metadata for JPEG files and TIFF files, but doesn't show metadata for GIF files. I did a brief search for other programs that show such metadata, but didn't find one that looked like it would extract all metadata except for the Metadata Extraction Tool, which seemed a bit cumbersome to use and I didn't try it.

Related findings: ThumbsPlus uses both IPTC Captions and JPEG Comment fields to create its annotations. I wrote some notes about annotations, captions, and comments in ThumbsPlus, and also some notes about how the way ThumbsPlus uses these produces some strange behavior in ThumbsPlus. I recommend that ThumbsPlus users not use both image comments and IPTC annotations.

Metadata in image files

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