Listing images with dpi resolution

M
Posted By
martinskultety
Nov 19, 2003
Views
1174
Replies
6
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Closed
Hi,

I have a collection of folders with thousands of images (JPG and TIF). Unfortunately their dpi resolution is not consistent…

To sort them out without having to open every single file, my goal is to generate a list of all images with their respective dpi resolution, something similar to this:

picture1.jpg 350 dpi
picture2.jpg 320 dpi
picture3.jpg 180 dpi
etc.

Is Photoshop or any shareware able to generate such a list?

Thanks for your help. Martin
Related Tags
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J
JJS
Nov 19, 2003
"Martin Skultety" wrote in message
Hi,

I have a collection of folders with thousands of images (JPG and TIF). Unfortunately their dpi resolution is not consistent…

To sort them out without having to open every single file, my goal is to generate a list of all images with their respective dpi resolution, something similar to this:

picture1.jpg 350 dpi
[…]
Is Photoshop or any shareware able to generate such a list?

(I’m answering withthout a definitive answer hoping to provoke input.)

It think it is highly unlikely you can get DPI from the image because all that is there, really, is pixels. If you assume target dimensions, then you can do some arithmetic to calculate and therefore show "dpi" as pixels-per-inch (PPI) for that target size . WindoZe shows pixel dimensions of GIF and JPEG files, but I don’t know where it gets it. Of the 23 NT file attributes I know (there may be more), none concern pixel size. Does anyone know where WindoZe finds that information? Is it caluculated by knowing type of file (.ext) then cluster factor and file size?
T
tacitr
Nov 19, 2003
It think it is highly unlikely you can get DPI from the image because all that is there, really, is pixels.

With most image formats, the header of the file lists the pixel dimensions and the resolution.

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Warren Sarle
Nov 19, 2003
"Martin Skultety" wrote in message
I have a collection of folders with thousands of images (JPG and TIF). Unfortunately their dpi resolution is not consistent…

To sort them out without having to open every single file, my goal is to generate a list of all images with their respective dpi resolution, something similar to this:

picture1.jpg 350 dpi
picture2.jpg 320 dpi
picture3.jpg 180 dpi
etc.

Is Photoshop or any shareware able to generate such a list?

This is another task that is easy to do with a script if you are familiar with scripting. But why do you care about "dpi"? It’s an arbitrary value that rarely has any important effect on anything, unless your printer software is really primitive.
J
JJS
Nov 19, 2003
Following my own post (silly me) – Okay, the GIF (and I presume JPEG) images do have the pixel dimensions stored in the header; specifically for GIF 89a (89a) in the Image Descriptor Block. There is a lot other data as well. At this point I depart, not wishing to cut code again, ever in my life. 😉
M
martinskultety
Nov 20, 2003
If the resolution is stored in the header of the image, is there any application able to list the resolution of every image within a folder?
J
JJS
Nov 20, 2003
"Martin Skultety" wrote in message
If the resolution is stored in the header of the image, is there any application able to list the resolution of every image within a folder?

Resolution is a misnomer. It does not exist. Only pixels exist, but I know what you mean, so for all practical purposes, look in the program that is the subject of this list. Photoshop V7 does that. See the Browser (Window-> File Browser). Mess with the little arrows at the bottom of the browser to get what you want. You probably want to look at rank: ‘resolution’, ‘details’. ‘Resolution (per se) will be in bold. If that feature does not suit you, then try ACDSee.

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