Windows 7 Supports Logon Background Customization

Windows 7 Logon Background Image before and after customisation

WithinWindows is reporting that the upcoming OS from Microsoft will support Logon screen Customisation. Although this has been done since Windows xp days with the use of software from Stardock and the likes, but official support means no messing with sensitive files or things going awry. It is reported that this functionality is for OEMs but it can be turned on and off by editing windows registry and using your own images.

Imagine putting your image on logon screen to let people know who the owner is or valentine day gift PC/laptop/netbook for your girlfriend/boyfriend with your image as the logon screen so that they see you every time they logon, just a thought !

On to hacking the registry to enable this feature. Quoting WithinWindows.com

First, a check is made to determine if the customization functionality is enabled or not. More precisely, a DWORD value named OEMBackground in the HKLM\Software\Microsoft\Windows\CurrentVersion\Authentication\LogonUI\Background key is checked. Its data, of Boolean type, defines whether or not this behavior is turned on, i.e. 1 for enabled, 0 for disabled. This value may not exist by default, depending on your system.

Afterwards, if customization is enabled, the primary monitor’s screen height and width are retrieved via calls to GetSystemMetrics. These values are used in the computation of the screen width (w)/height (h) ratio. For example, my desktop resolution is 1920×1200. The ratio, computed by the division of w/h, is 1.6:1.

The result of this computation is looked up in an internal table that drives what image to load on disk. Although I don’t have a large enough monitor to test, it appears resolutions higher than 1920×1200 will force the loading and zooming of an image of closest compatibility (i.e. same ratio, smaller image).

As this is an OEM feature images are derived from %windir%\system32\oobe\info\backgrounds. Like the registry value, this folder may not exist by default. The following files (sorted by width-to-height ratio) are supported in this folder:

• backgroundDefault.jpg
• background768×1280.jpg  (0.6)
• background900×1440.jpg  (0.625)
• background960×1280.jpg  (0.75)
• background1024×1280.jpg (0.8)
• background1280×1024.jpg (1.25)
• background1024×768.jpg  (1.33-)
• background1280×960.jpg  (1.33-)
• background1600×1200.jpg (1.33-)
• background1440×900.jpg  (1.6)
• background1920×1200.jpg (1.6)
• background1280×768.jpg  (1.66-)
• background1360×768.jpg  (1.770833-)

The backgroundDefault.jpg image is loaded and stretched-to-fit when a resolution/ratio-specific background cannot be found. The other resolution/ratio-specific files are self-explanatory. If the background cannot be loaded (e.g. image physically too large, incorrect ratio, etc.), the default SKU-based image is loaded from imagesres.dll. You’ll see a Windows Server-themed grayish background in there, too, suggesting this functionality is not specific to client SKUs.

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