The wallpaper you use often is something you think you're comfortable with, but it's not as good as it appears on Windows 10.
This does not refer to the problem of the wallpaper itself, but to the system.
To reduce the consumption of system resources, WIN10 defaults to the custom wallpaper, which is only 85% of the original image.
If your computer processor, memory is not the standard of the classic machine, do not try to restore to 100% quality.
Here are the steps:
1.Windows key +r Enter "regedit" to open Registry Editor
2. Navigate to HKEY_CURRENT_USER\Control Panel\Desktop (build 14942 preview and update users can paste directly to the address bar)
3. right pane blank Space click-New DWORD (32-bit) value, named Jpegimportquality
4. Double-click the new DWORD and enter the number 100
5. Click OK to save
6. Restart the computer, and then replace the wallpaper after the entry into force.
Now, your local wallpaper will not be compressed by the system default.