Exiftool generated json file: Exposure Time representation

[exifacou]

Exiftool generated json file: Exposure Time representation

I'm writing a Swift program on my Mac that uses standard json decoding/encoding. The program reads a json file generated by Exiftool.

Example:

> exiftool -struct -j -ExposureTime -m -q -ext JPG . > images_ETselect.json

Result

[{
  "SourceFile": "./image-1.jpg",
  "ExposureTime": "1/125"
},
{
  "SourceFile": "./image-2.jpg",
  "ExposureTime": 1
},
{
  "SourceFile": "./image-3.jpg",
  "ExposureTime": 1.6
},
{
  "SourceFile": "./image-4.jpg",
  "ExposureTime": "1/13"
},
{
  "SourceFile": "./image-5.jpg",
  "ExposureTime": "1/640"
}]

Unfortunately the type of data generated for ExposureTime isn't always the same. For fractions it writes a string "1/8" which is exactly what I want.

But when Exiftool comes to an image with numbers, by example 1, 8, 1.6 ... it outputs a number not a string. Swift doesn't like this. My program crashes because of different data types for tag ExposureTime ...

debugDescription: "Expected to decode String but found number instead."

I read the exiftool manual but didn't find an example that describes what exiftool parameter I could set so that it always delivers a string for ExposureTime. Any idea how to do this?

Many thanks for your hints!

[Phil Harvey]

You could either add -n to the command to always output a real number, and/or -API StructFormat=JSONQ to always output the value as a string.

- Phil

[Phil Harvey]

I'll add this to the documentation of the -j option:

    Note that ExifTool quotes JSON values only if they don't look like numbers
    (regardless of the original storage format or the relevant metadata
    specification).  This may be a problem when reading the JSON via a strongly
    typed language.  However, the API StructFormat option may be set to "JSONQ"
    to force quoting of numbers.  As well, the B<-sep> option may be used to
    convert arrays into strings.  For example:
   
        exiftool -j -api structformat=jsonq -sep ", " ...

- Phil

[exifacou]

As well, the B<-sep> option may be used to
    convert arrays into strings.

I had such a problem with "Keywords". In the case of only one keyword I got a string and not an array of strings which also caused problems. I solved it using XMP:Subject instead plus -struct option.

[exifacou]

Now tried this

exiftool -struct -j -ExposureTime -API structformat=jsonq -m -q -ext JPG . > images_ETselect.json

unfortunately besides the "String fractions" still numbers are delivered. Never worked with the API options. So I might do it wrong ...

[StarGeek]

Make sure you update to at least version 12.88, as that is where the JSONQ option was added.

[exifacou]

Sorry, I'll try this tomorrow. Many thanks!

[exifacou]

Updated to 13.02 - Works - Great, many thanks!