If we cracked open a TIFF file with a hex editor we wouldn’t find the text “ImageWidth” as a searchable entity, but we would find the tag code 0x0100 if we knew where to look. Each of these tags has a code – so the metadata field “ ImageWidth” has the numerical code 256 (decimal) / 0x0100 (hexadecimal). For example, the TIFF standard has some useful baseline tags. The image parser finds the number, looks up its label, and then processes the information accordingly.

On the surface it looks like the tags are maintained as named items inside the file, when actually, each of the tags is assigned a number, the tag number and its corresponding value or property is recorded into the file. The tags are essentially the data containers that hold each of the little bits of data that comprise the metadata/information we’ve just exposed via exiftool/JHOVE. The error is reported by JHOVE because tagged image formats require the tags to recorded in numerical sequence order. Lets look at how we might start to address the sequence issue. We’ve seen how we can view the metadata via exiftool. Fire up JHOVE and take a look at what it says (drag and drop your file onto the GUI) Now would be a good time to check the image in JHOVE. You can use whatever filename makes sense to you. This “pipes” the metadata in a new file called cover_metadata.txt. You can save this data to a text file with the following command:Ĭ:>exiftool cover.jpg > cover_metadata.txt You should see metadata relevant to your file. Test exiftool works by typing exiftool and you should see a dump of all the commands you can use. Next up, open up commandline (“start menu” > type/find “cmd”). In that folder place your image(s) and the exiftool executable. We found one in our collections that is open access It would be useful to find an image that has the tag sequence issue. (I’m not going to go through JHOVE installation – the working assumption is you installed it OK).

You’ll also want the excellent JHOVE to check your work. You’ll need the excellent exiftool, download and extract. You might want to skip a few steps if you’re comfortable with command-line operations. The steps in the process assume zero knowledge and windows working environment. At the end of the post we’ll talk a little bit about the implications of the method for collection items.

We are sharing it for comment and discussion. It seems like the sort of thing that others might find useful, and so this blog is a record of that method. We were asked recently to write up a tactical fix for addressing “Tag out of sequence” errors in image files.

Using exiftool