Zero-DPI image causes division by zero error

[ColonelThirtyTwo]

This image reports a DPI of "zero inches" which is obviously invalid:

Resolution Unit : inches
X Resolution : 0
Y Resolution : 0

This causes a division by zero error when attempting to use it in a document.

Admittedly, while the info is bogus, it should be easy to catch and handle as an image lacking DPI info.

[scanny]

Hi Alex, can you provide a stack trace and what's your best sense of what a fallback behavior should be?

One idea would be to set the resolution to the default (72 if memory serves), which is at least as valid as zero I suppose :)

[ColonelThirtyTwo]

I'll try to get a stack trace tomorrow.

72 DPI i feel is a reasonable default. The code should already be handling images that don't have DPI information, so it should do the same thing.

[emcezet]

Hey, I think I ran into the same problem, here is the traceback (w/ sanitized paths). The error is thrown when a JPG does not have the DPI set.

Traceback (most recent call last):
 File "main.py", line 198, in _export_docx 
 _add_media(url)
 File "main.py", line 147, in _add_picture 
 document.add_picture(path)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "C:\Python\Python312\Lib\site-packages\docx\document.py", line 138, in add_picture
 return run.add_picture(image_path_or_stream, width, height)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "C:\Python\Python312\Lib\site-packages\docx\text\run.py", line 79, in add_picture
 inline = self.part.new_pic_inline(image_path_or_stream, width, height) 
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 
 File "C:\Python\Python312\Lib\site-packages\docx\parts\story.py", line 72, in new_pic_inline
 cx, cy = image.scaled_dimensions(width, height)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "C:\Python\Python312\Lib\site-packages\docx\image\image.py", line 135, in scaled_dimensions
 return self.width, self.height
 ^^^^^^^^^^
 File "C:\Python\Python312\Lib\site-packages\docx\image\image.py", line 108, in width
 return Inches(self.px_width / self.horz_dpi)
 ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~
ZeroDivisionError: division by zero

I'm sorry that I don't have enough time to learn how your codebase works and what the proper fix should be - I created a hotfix for myself in the image.py:

 @property
 def horz_dpi(self) -> int:
 """Integer dots per inch for the width of this image.

 Defaults to 72 when not present in the file, as is often the case.
 """
 if self._image_header.horz_dpi is None or self._image_header.horz_dpi == 0:
 return 72
 return self._image_header.horz_dpi

 @property
 def vert_dpi(self) -> int:
 """Integer dots per inch for the height of this image.

 Defaults to 72 when not present in the file, as is often the case.
 """
 if self._image_header.vert_dpi is None or self._image_header.vert_dpi == 0:
 return 72
 return self._image_header.vert_dpi

With this change I could move forward with my project and the JPG image is properly included, I hope that this is enough to help you create a proper fix ;)