Writing arrays into exif segment is not working

[xavieldar]

Some Exif tags store a list of values, such as GPS latitude and longitude, which take a list of three rationals to store the angle in a "degrees minutes seconds" format.

For example, one would expect to be able to write something in the form

image.modify_exif({
    'Exif.GPSInfo.GPSLongitude': ['30/1', '50/1', '12345/1000'],
    'Exif.GPSInfo.GPSLatitude': ['30/1', '50/1', '12345/1000'],
})

and read back successfully the values.

Looking at the api C++ code, arrays seems to be supported in the XMP segments. I believe that porting the same behaviour to the exif part should be straightforward.

Thanks for the good work!

[LeoHsiao1]

Hi!
There are many types of metadata, so I didn't try to see if each tag could be modified.

I tried to read the tag you mentioned and found it was like this:

>>> import pyexiv2
>>> img = pyexiv2.Image(r'C:\Users\Leo\Desktop\IMG_20200105_115821.jpg')
>>> img.read_exif()['Exif.GPSInfo.GPSLongitude']
'114/1 2/1 426696/10000'

So I modified it in the same format. It works:

>>> img.modify_exif({'Exif.GPSInfo.GPSLongitude': '200/1 2/1 400000/10000'})
>>> img.read_exif()['Exif.GPSInfo.GPSLongitude']
'200/1 2/1 400000/10000'

Next, you just need to convert it from string to list:

>>> '200/1 2/1 400000/10000'.split(' ')
['200/1', '2/1', '400000/10000']
>>> ' '.join(['200/1', '2/1', '400000/10000'])
'200/1 2/1 400000/10000'

Does that solve your problem?

[xavieldar]

Hi,

Thanks for the quick answer. Actually, that works, thanks!

I though I tried that, but I was converting Fraction object into string directly with fractions.Fraction.__str__(), which does not print out the denominator when equals to 1, which gave me:
'30 50 12345/1000' instead of '30/1 50/1 12345/1000', and would not work… This is fixed on my side and I can properly geotag images.

Thanks.

[github-actions]

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