Some Windows 10 users could notice that when setting a JPEG image as the desktop wallpaper, the quality of the wallpaper is reduced in compared to the original image. The number of image artifacts has increased and is more obvious on large screens. The problem is not new, and could be observed in Windows 7 or Windows 8, with the image quality reduced by 15%. But only in Windows 10 you can now manage such system behavior.
When setting a JPEG image as a wallpaper, Windows automatically reduces its quality to 85%. Consequently, the size of the file is also reduced. This is done to reduce the size of allocated memory for the wallpaper and to save space on the disk. Thus, Microsoft tries to reach an optimal compromise between the image quality, the image size and the system performance.
The system stores the converted image in a file named TranscodedWallpaper inside the directory C:\Users\%username%\AppData\Roaming\Microsoft\Windows\Themes\. If you change the extension of this file to *.jpg, you can view the image used as the wallpaper.
You can manage the image compression level only through the registry.
- Open the Registry Editor (regedit.exe)
- Go to HKEY_CURRENT_USER\Control Panel\Desktop
- Create a new 32-bit DWORD parameter with the name JPEGImportQuality
- The value of this parameter is between 60 and 100 (in the decimal system). The value of 100 means using the highest-quality wallpaper (without compression). By default, the system uses the value of 85.
- Log off the system.
- After you log on again, set the image you need as a wallpaper. It has to be displayed without compression.