ZoomBrowser Ex thumbnail cache
Digital Preservation Notes
Documentation on the file is lacking but its purpose seems to be to support the display of image thumbnails in the Zoombrowser Ex application. Images are indexed and a lower resolution version created, and stored in the file, to be rendered as a thumbnail in the Zoombrowser window. ZbThumbnail files are created for each folder that is indexed by the tool. The file is created as a Windows 'hidden' file and its existence would not be known by the majority of users with a default configuration in Microsoft Windows. The file might contain information not elsewhere present in the Windows system. For example, even in a folder with no images, its existence suggests that images were once present and viewed using Zoombrowser Ex.
Thumbnail files can be extracted from the object using forensic techniques and we can see what was once there and indexed. The file also seems to maintain a textual component, e.g. the corresponding file names for the images, and in some cases it seems that more file names exist than thumbnails. This is difficult to verify without an open specification for the object. The user would have little or no knowledge of this file, or its content.
This file supports ZoomBrowser Ex, an application independent to Microsoft Windows.
The majority of the payload of the object are the thumbnails themselves. The last byte of the file is the trailing bytes of the last plain-encoded JPEG thumbnail file (
0xFF 0xD9). The images can be extracted by searching for the opening bytes of a JPEG (
0xFF 0xD8) and reading the following bytes up to a corresponding footer - this process is then repeated for the entire file.
Work needs to be done to understand if the file maintains a count of the number of objects one should be able to extract.
Work also needs to be done to understand how to pair image objects with their corresponding file names.
Files apparently begin with the ASCII signature "
- Examples can be found by searching the web for "index of" zbthumbnail.