[Libreoffice-bugs] [Bug 116164] New: Cropped JPEG images get distorted when changing monitor resolution

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=116164

            Bug ID: 116164
           Summary: Cropped JPEG images get distorted when changing
                    monitor resolution
           Product: LibreOffice
           Version: 5.4.5.1 release
          Hardware: All
                OS: All
            Status: UNCONFIRMED
          Severity: normal
          Priority: medium
         Component: Impress
          Assignee: libreoffice-bugs at lists.freedesktop.org
          Reporter: robert_averbeck at web.de

Description:
When importing a JPEG picture Impress will try to read the resolution (dpi,
ppi) from the JFIF tag. If this tag is not present Impress will use the
resolution of the current monitor instead. Since the odp file format uses
length units (e.g. cm) when defining image cropping, the crop values of images
without JFIF tag need to be changed when changing the monitor resolution,
otherwise these images get distorted. Unfortunately most digital cameras do not
use the JFIF tag but the IFD0 tag. Please note that using a machine dependent
default makes odp documents machine dependent. This explains user complaints
about image distortion when exchanging documents between different machines.

Steps to Reproduce:
1.Import a JPEG file from a digital camera into Impress.
2.Crop the image in one dimension and save the odp file.
3.Opening this file on a machine with different monitor resolution

Actual Results:  
Image is displayed (and printed) in correct size but distorted.

Expected Results:
odp files should be machine independent.


Reproducible: Always


User Profile Reset: Yes



Additional Info:
Suggest fix: When importing a JPEG image which does not have a JFIF tag, look
for an IFD0 tag. If both tags are missing, use a constant (machine independent)
default value for resolution. Any fix for this bug will change the display of
some existing documents. Therefore, I suggest supplying a tool that prompts the
user for a dpi value and converts all odp files in a given directory.


User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
Firefox/52.0

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