DPI resolution not read/written correctly for some JPEGs

[galfar]

The issue is caused by missing JFIF header in the file - only EXIF is present.

Adobe's SW apparently switched to EXIF only recently:
https://feedback.photoshop.com/photoshop_family/topics/jpeg_format_different_between_cs2_and_cs6?topic-reply-list%5Bsettings%5D%5Bfilter_by%5D=all

To fix this we need to read and parse EXIF data which is in fact a TIFF directory. So if LibTiff that Deskew already uses could be reused for this then fixing this would not take that much time. Otherwise this will have to wait.

Test image:

[galfar]

Clarification: problem is not that Deskew cannot write DPI value to output JPEG files. It cannot read DPI of the input and then does not know what to write to the output (and leaves the default).

A workaround (and maybe generally useful) would be an option to force DPI of the output to certain value.