Image exif_transpose not working with Pillow 7

[jguerriat]

Hi!
First, sorry if my question is not fully documented, i'm not exactly used to work with pillow.

I'm working on a ERP called "odoo". When uploading a picture, it gets treated by pillow then saved into a filestore.
One of our client had a problem when trying to upload some of its picture. Some of then did work fine, others provoke this error:

  File "[...]parts/odoo/odoo/tools/image.py", line 383, in image_fix_orientation
    return ImageOps.exif_transpose(image)
  File "[...]lib/python3.6/site-packages/PIL/ImageOps.py", line 549, in exif_transpose
    transposed_image.info["exif"] = exif.tobytes()
  File "[...]lib/python3.6/site-packages/PIL/Image.py", line 3258, in tobytes
    return b"Exif\x00\x00" + head + ifd.tobytes(offset)
  File "[...]lib/python3.6/site-packages/PIL/TiffImagePlugin.py", line 808, in tobytes
    data = self._write_dispatch[typ](self, *values)
TypeError: write_undefined() takes 2 positional arguments but 5 were given

The Pillow version used is 7.0.0. (6.0.0 gave me another error, while 4.0.0 works fine!)

When i tried to modify the image (simply by rotating it in the default MacOs app: Preview), some exif information got deleted and then i was able to upload those pictures (i compared before/after exif using a website).

I tried to use an exif editor to check exactly what metadata caused this issue, but i wasnt able to find an editor that allowed me to edit the metadata "Orientation", which i highly suspect causes the issues.

In the original picture, the orientation metadata was: Rotate 90 CW
In the modified picture, the orientation metadata is: Horizontal (normal)

You'll find attached both image, if it can help you diagnose where the problem lies.

The first image works fine, the second one does not work.

[jguerriat]

Here is the tag that seems to make it fail:

Tag 42034, Type: 7, Value: ((4, 1), (6, 1), (9, 5), (12, 5))

it seems that tag 42034 refer to LensSpecification.

[QuintenDV]

I'm having problems with this as well.
If you don't care about the other exif tags you can solve this by deleting them.

exif = image.getexif()
# Remove all exif tags
for k in exif.keys():
    if k != 0x0112:
        exif[k] = None # If I don't set it to None first (or print it) the del fails for some reason. 
        del exif[k]
# Put the new exif object in the original image
new_exif = exif.tobytes()
image.info["exif"] = new_exif
# Rotate the image
transposed = ImageOps.exif_transpose(image)

This removed all the exif tags except for the one that contains the orientation information (0x0112), and rotates the image.

[kkopachev]

To add a little context.
The issue is happening because for tag 42034 it's expected to have 4 rationals. Right now, Pillow only supports writing 1 Rational/SRational value per tag. Other types should be fine, looking at the code.

[radarhere]

It's unclear what is meant when the original post states that this worked in Pillow 4.0, when ImageOps.exif_transpose was only added in Pillow 6.0.

[jguerriat]

Indeed, i understood afterward what was going on. Basically, odoo uses that method or not, depending on pillow's version :)

[mikesongming]

Also failed when value of tag is empty as "{}".

Relevant code for PIL.TiffImagePluginImageFileDirectory_v2.to_bytes is problematic [line 584-592]. The line dest[tag] = values[0] failed for many cases.

---

try:
     (dest[tag],) = values
except ValueError:
     # We've got a builtin tag with 1 expected entry
     warnings.warn( 
     "Metadata Warning, tag %s had too many entries: %s, expected 1"
            % (tag, len(values))
     )
     dest[tag] = values[0]