Author Topic: Using exiftool to change dpi value  (Read 5140 times)

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Using exiftool to change dpi value
« on: May 12, 2010, 08:54:23 AM »
[Originally posted by antonb on 2008-08-10 20:12:42-07]

I hope you can help. I have jpeg images without EXIF headers. When I use Exiftool to change the dpi (exiftool -Xresolution=300 -Yresolution=300 *.jpg) to 300dpi, Exiftool creates an exif header with this information. When I submit these images to photo libraries, they do not recognize the exif header, and uses the the dpi embedded in the jpeg-header. The problem is that Exiftool changes the previous dpi to 300, but only for images that had a pevious dpi value. Some of my images does not have a dpi value embedded in the jpeg header, and for these images Exiftool does not change the dpi to 300. When I open these images in Irvanview after using exiftool, it still shows no value for the dpi. Should I use exiftool in another way for these images?

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Re: Using exiftool to change dpi value
« Reply #1 on: May 12, 2010, 08:54:24 AM »
[Originally posted by exiftool on 2008-08-15 12:10:37-07]

There is no resolution information in the JPEG standard.  I think
you are talking about JFIF/JPEG information, which technically should
not exist in an EXIF/JPEG image.  However, some image utilities
rely on this (and many write JFIF when EXIF already exists), so
you can do this if you want.  ExifTool will not create the JFIF
segment unless you specifically write the JFIF information.  ie)

-jfif:Xresolution=300 -jfif:Yresolution=300

- Phil

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Re: Using exiftool to change dpi value
« Reply #2 on: May 12, 2010, 08:54:24 AM »
[Originally posted by antonb on 2008-08-19 22:32:19-07]

Thanks Phil. Works perfectly. I appreciate your advice.