jpeg file creation question

dav · 09-02-2004, 09:34 AM

i use a mac in a windows environment and create jpegs of illustrations which are used in documents.
when saving as a jpeg, an additional file is created, visible only to the windows machines on the network. for example i'll save a file as "test.jpg" in a folder on the network. "test.jpg" will be the only file visible to me on my mac, however the windows pcs will see a grayed out file "._test.jpg" as well as the "test.jpg" file. i believe this is created by the mac os, as different applications produce the same result (._name.jpg). has anyone else seen these types of file, and have an understanding of why they're there/how to not have them be created?

thanks.

mac is running os x 10.3.5
pc's are running windows xp

DoubleEdd · 09-02-2004, 09:48 AM

They're the resource fork for the file. They can be deleted but you'll lose the icon for the file (it'll revert to the default) and a few other bits of metadata about it. I'm not aware of any way you can prevent them from being created, but maybe the Windows machines or the file server can be set to hide them so that the Windows users don't see them?

yellow · 09-02-2004, 10:04 AM

It's exactly as DoubleEdd said. The Mac OS "invisibly" stores file information in 2 forks, the data fork and the resrouce fork. The data fork contains, naturally, the actual data. The resource fork contains info about which app opens the jpeg, etc.

How are these files being transfered to the Windows boxes?
Which applications is being used to create these jpegs?
Is it being created in OS X (native) or under Classic?

dav · 09-02-2004, 10:17 AM

The files are created natively in MacOS X 10.3.5 from either Photoshop, or CorelDraw, and saved into a common folder on a server. The Windows boxes access the folder and see the additional files along with the JPEGs. These additional files have added some confusion to the Windows folks who need to access the "real" JPEGs.

hayne · 09-02-2004, 11:31 AM

In most graphics apps, there is an option to save files as "cross-platform" or "Internet ready" or "flattened". These all mean the same thing - that the resource fork is not saved. That's one way to solve the problem - tell your users to use this option (whatever it is called on your apps).

frankko · 09-02-2004, 11:43 AM

If you use Save For Web (rather than Save As...) in Photoshop, it won't create a resource fork.

blubbernaut · 09-02-2004, 07:04 PM

I've seen some apps on versiontracker.com that will strip the resource fork from JPEGS. You could set up a folder with a folder-action to automatically do this to all JPEGS saved to that folder

09-02-2004, 09:34 AM	#1
dav Prospect Join Date: Jul 2004 Posts: 4	jpeg file creation question i use a mac in a windows environment and create jpegs of illustrations which are used in documents. when saving as a jpeg, an additional file is created, visible only to the windows machines on the network. for example i'll save a file as "test.jpg" in a folder on the network. "test.jpg" will be the only file visible to me on my mac, however the windows pcs will see a grayed out file "._test.jpg" as well as the "test.jpg" file. i believe this is created by the mac os, as different applications produce the same result (._name.jpg). has anyone else seen these types of file, and have an understanding of why they're there/how to not have them be created? thanks. mac is running os x 10.3.5 pc's are running windows xp

Thread Tools
Show Printable Version Email this Page
Display Modes	Rate This Thread
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode	Rate This Thread:

09-02-2004, 09:48 AM	#2
DoubleEdd Major Leaguer Join Date: Nov 2002 Posts: 285	They're the resource fork for the file. They can be deleted but you'll lose the icon for the file (it'll revert to the default) and a few other bits of metadata about it. I'm not aware of any way you can prevent them from being created, but maybe the Windows machines or the file server can be set to hide them so that the Windows users don't see them?

09-02-2004, 10:04 AM	#3
yellow Moderator Join Date: Jan 2002 Posts: 10,677	It's exactly as DoubleEdd said. The Mac OS "invisibly" stores file information in 2 forks, the data fork and the resrouce fork. The data fork contains, naturally, the actual data. The resource fork contains info about which app opens the jpeg, etc. How are these files being transfered to the Windows boxes? Which applications is being used to create these jpegs? Is it being created in OS X (native) or under Classic?

09-02-2004, 10:17 AM	#4
dav Prospect Join Date: Jul 2004 Posts: 4	The files are created natively in MacOS X 10.3.5 from either Photoshop, or CorelDraw, and saved into a common folder on a server. The Windows boxes access the folder and see the additional files along with the JPEGs. These additional files have added some confusion to the Windows folks who need to access the "real" JPEGs.

09-02-2004, 11:31 AM	#5
hayne Site Admin Join Date: Jan 2002 Location: Montreal Posts: 31,957	In most graphics apps, there is an option to save files as "cross-platform" or "Internet ready" or "flattened". These all mean the same thing - that the resource fork is not saved. That's one way to solve the problem - tell your users to use this option (whatever it is called on your apps).

09-02-2004, 11:43 AM	#6
frankko All Star Join Date: Jan 2002 Location: New York, NY Posts: 587	If you use Save For Web (rather than Save As...) in Photoshop, it won't create a resource fork.

09-02-2004, 07:04 PM	#7
blubbernaut MVP Join Date: Sep 2003 Posts: 1,856	I've seen some apps on versiontracker.com that will strip the resource fork from JPEGS. You could set up a folder with a folder-action to automatically do this to all JPEGS saved to that folder