Closed GoogleCodeExporter closed 9 years ago
The jpeg cinfo.density_unit field for this image is 0, which means that the
resolution is not defined. No idea how identify arrives at 180 ppi. Is there
any reason to believe the resolution should be 180 ppi?
For pixels/inch (ppi), that field must be 1.
For this image, the values in cinfo.X_density and cinfo.Y_density are both 1.
gimp interprets undefined density as 1 pixel/pt = 72 ppi. Pretty arbitrary.
leptonica uses 0.
Original comment by dan.bloo...@gmail.com
on 4 Jun 2012 at 9:16
I can not guarantee that image has 180 DPI (well this is information I am
looking for).
But IrfanView show nothing if there is no DPI info and in this case it shows
180. So I tried to test it with Imagick and it "proves" that DPI is 180 ;-).
I got another idea today - if exif info do not store resolution and it looks
like this could be case: I tried it in http://regex.info/exif.cgi and it shows
this information:
Resolution 180 pixels/inch
X Resolution 72
Y Resolution 72
Original comment by zde...@gmail.com
on 12 Jun 2012 at 2:28
I removed exif info and Imagick, IrfanView and XnView shows image has 180 DPI...
So there should be other way how to get info about resolution...
If it helps image was created by camera...
Original comment by zde...@gmail.com
on 18 Jun 2012 at 8:39
On Windows 7, using ACDSee to view the sample jpeg shows EXIF metadata has X
Resolution & Y Resolution set to 180/1 and Resolution Unit is inches. IrfanView
shows same thing.
After cleaning all exif metadata using exiftool [1] via the following command:
exiftool -all= P1140724.JPG
ACDSee & Irfanview both don't show any value for X & Y Resolution. So, IMO, the
exif metadata *is* how this is determined for jpeg files.
IMO, especially for OCR purposes, people should *not* use jpeg and instead use
lossless TIFF or PNG and make sure the resolution is set correctly.
[1] http://www.sno.phy.queensu.ca/~phil/exiftool/
Original comment by tomp2...@gmail.com
on 26 Jun 2012 at 10:40
Thanks, Tom. Not looking forward to parsing exif in jpeg.
Seems like low priority.
Original comment by dan.bloo...@gmail.com
on 27 Jun 2012 at 3:49
1.70 is out. You can get it at leptonica.org/download.html
It still doesn't parse exif fields in jepg for hidden resolution ;-)
Original comment by dan.bloo...@gmail.com
on 24 Jan 2014 at 6:49
Original issue reported on code.google.com by
zde...@gmail.com
on 4 Jun 2012 at 7:17Attachments: