Preview in Snow Leopard not opening images properly

Apple's "Preview" application is an exceptionally useful tool for managing photos in the Finder and performing simple manipulations of the photos, and has become quite popular; however, there are a couple of small problems people have had with using Preview in Snow Leopard, including images not opening in the main window, and groups of images not loading fully when opened.

Sidebar images not loading

Upon selecting and opening a batch of images, Preview usually keeps them in the program's sidebar, only showing the selected one in the main window. Some people have notices that this does not happen for all images, and while they will load in the sidebar just fine, certain ones will not display in the main window when selected, leaving the program with a blank white window.

There may be two possible reasons for why this is happening. First, be sure you have selected only one image in the sidebar, since multiple selections may prevent Preview from displaying them in the main window, especially if one is corrupted. Click through images and use the arrow keys to ensure the program has only one image highlighted. If the program still does not load some images, try opening it in 32-bit mode by getting information on Preview in the Finder and checking the box to open it in 32-bit mode. Application support for 64-bit processing has not come without small bugs like this, and the option to open programs with the older 32-bit code can get the program working again in the event that these bugs occur. Since for the most part Preview will not need to use more than 4GB of RAM, the benefits of using it in 64-bit mode will not be used or needed by most people, so it should make no difference to run it in 32-bit mode.

Groups of images not opening

Another problem is that preview may not open all the images in a selected group in the Finder. If opened, only a subset will load in Preview, but upon closing the program and trying again the program will be more successful, opening additional pictures until eventually all of the selection is opened. This happens more prevalently for new pictures on the system (ie, downloaded from the internet or from a camera), and after images have been opened then this problem will not happen for them.

This behavior may be due to the quarantine flag the system places on newly downloaded items, including pictures. When you download an application from the internet, this flag will cause the system to present a warning about the program being from the internet. The same goes for pictures, and while the warning will not be displayed, the system and various programs may not allow them to be opened unless they are explicitly targeted for opening. Opening a group of images may cause this behavior, and when the first image with a quarantine flag is found the opening will pause, but upon subsequent openings the system will not pause on the same file and instead will pause on the next one with a quarantine flag.

If this problem regularly occurs, you can remove quarantine flags from files using a Terminal command. The quarantine flag is appended to a file using extended attributes, and the following command will remove them:

xattr -d com.apple.quarantine FILENAME

If you wish to apply this command to a number of files, you can either put them in a directory and run the command on the contents of the directory with the syntax "xattr -d com.apple.quarantine /DIRECTORYPATH/*" or you can enter the command for multiple items as follows:

1. Type "xattr -d com.apple.quarantine" in the Terminal followed by a space.
2. Select and drag the desired items to the Terminal window.
3. Press the enter key when all the filenames and paths have been entered.

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