Using the command exiftool foo.jpg -xresolution=128 -v2
returnsJPEG APP1 (4654 bytes):
Rewriting XMP
[XMP rewritten with no changes]
while afterwards
exiftool -ALL:ALL foo.jpg"-v2 | grep -i Resolution
returnsResolution Unit : None
X Resolution : 128
Y Resolution : 128
X Resolution : 128
Y Resolution : 128
Resolution Unit : Unknown (0)
Resolution Unit : Inch
X Resolution : 300
Y Resolution : 300
And using ImageMagick and exiv2, the same unchanged XMP Resolutions are returned. This is in a single console tab, i.e., one main BASH shell (ignoring subshells spawned and unterminated from running scripts).
And in version 0.84 x32 of XnViewMP, the resolution is now 128 in the general Properties tab and XMP tab (Browser mode) . The "physical" dimensions factor to what they would be if a printer could print at precisely 128dpi.
So why is Exiftool hesitating, or deeming it unnecessary, to change the XMP Resolutions from 300 to 128, if this is what's happening?
Carver
What's the result of
exiftool -*resolution -G1 -a -s FILE
Off hand, I'm guessing that XResolution and YResolution are in someplace incorrect, like XMP-exif instead of XMP-tiff.