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dpi problem?

RezzZ
on November 15th 2010

Hi!
I may have found a small bug or feature I don't understand :-).

I used resizer to change the dpi of an image from 300 to 96. I used resizer like this:
PhotoResizeD96Q85O.exe
this gives me a new file with DPI96 but the dimensions were also changed which I don't want so I added a 'T' to the file (I thought the T was to keep the pixel settings):
PhotoResizeD96TQ85O.exe
but this doesn't change anything...

I've been trying for a few hours now (yes really :S... what I really want is to resize images to xxx pixels with Quality set to 85 with original date and metadata but I don't seem to get the syntax right. It's always going wrong somehow.

Also, is there a way to use the source filename and add something like '_XL' to it instead of the width/height or dpi setting?

Can someone help me out here?

Vlasta
on November 15th 2010

When T is used, nothing is done to the pixels (->setting quality has no effect as the quality stays the same), it just writes the new resolution value into the header. Simple PhotoResizeD96T.exe should do that.

If T is not used, the tool tries to preserve the physical size of the image and calculates pixels or DPI automatically. If you want both, you'll have to do it in 2 steps.

_XL suffix can be added, but only if you are using it from command line with something like "-c<ROOT><PATH><NAME>_XL.jpg"

RezzZ
on November 16th 2010

thanx for your reply! If D96T only changes the header data of the image than why would you use that option? If it doesn't physically changes the image, I don't understand why the T option would be helpfull...

the _XL suffix works now :-). Tried the shortcut mode before but didn't get it to work. I does work now :-D, but I'm still not able to set the picturesize to 1200x? AND DPI to 96.
You say I have to do that in 2 steps and I already guessed as much but I can't figure out how. If I first set the pixel size to 1200x:
"PhotoResize.exe" -1200 -Q85 -M -E -O -c<NAME>_XL.jpg

It gives me a great image only DPI has to be changed now so I get a more internet friendly image (like 10 times smaller). What's my next step to change the dpi of the image (not just header) to 96 and keep the pixelsize 1200x823 ?
If I use something like this:
PhotoResizeMD96EO.exe
the DPI gets changed but dimensions also (it gets bigger again 1387x951)...

I also had to put the M in front of the D96 otherwise the DPI doesn't get changed and I just and up with a copy of the same image... Perhaps it would be a nice feature if PhotoResize automatically knows in which order it should use all settings?

Vlasta
on November 16th 2010

There is one limitation. The tool never modifies data within EXIF block. It either copies it or deletes it. (Because the EXIF standard was designed in an extremely stupid way and changing it requires using a very complicated and changing piece of code. I'll likely never do that in Picture Resizer. Maybe the EXIF authors did this on purpose to made a trivial thing complicated in order to charge for applications that solve this artificial problem. Nobody can be THAT stupid.)

Another problem is that the EXIF authors didn't know anything better than to put the resolution value into the the EXIF block as well. In case of .jpg file, you end with resolution specified in 2 places. Now what happens when they are different? Suffering.

Putting the M in front of D96 made the tool ignore the M option (it must be after that) and it deleted the meta-data including EXIF. Hence you saw the resolution from the header and not the resolution from the EXIF block in your viewer.

So, if you delete EXIF from the for-web versions, PhotoResizeD96T.exe does the trick. If you also want the value within the EXIF block changed, Picture Resizer cannot help you now.

RezzZ
on November 16th 2010

ok, I don't even remember why I wanted the EXIF anyways but I't more clear now and I'll drop the M ;-). thanx for your time!

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