Sadly (and I'd love to be proven wrong) the image must be in jpg format. The worst format for "lossy" images I can think of. However, back to the plot.
You are supposed to have images in all these formats, and with these filenames (I believe) to cover all eventualities if you are sharing,
image ratios in (brackets):-
Code:
backgroundDefault.jpg [COLOR=red](the actual image you will be using)[/COLOR]
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-)
Here's what I do on my own PC.
Get (Hopefully) my required image in either PNG or BMP format, convert it using Photoshop to jpg and select the "maximum" size settings for that format, in other words reduce the compression that knacks up the image as much as possible.
Now, I'm using screen resolution at 1280 x 768 settings, although my monitor is 1280 x 820, it's the closest I can get without excessive oval-ling of round objects. The image I use for my logon screen is 1920 x 1200 in size, its close enough to my aspect ratio to make little or no difference, I don't intend looking at it too long!!, and this should be named BackgroundDefault.jpg. Store this (BackgroundDefault.jpg) in your
C:\Windows\System32\oobe\INFO\BACKGROUNDS folder.
Make a .reg file with the following code.
Code:
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Authentication\LogonUI\Background]
"OEMBackground"=dword:00000001
Double click the .reg file and accept the warning prompt before merging and the next time you re-boot you should have a new Login/Welcome background.
You can also tie your login background to a specific theme if you change themes a lot but always return to your standard. To do this open your favourite .theme file with a text editor (notepad will do), which, if you've saved your theme, you will find in the folder at
C:\Users\Your User Name\AppData\Local\Microsoft\Windows\Themes When you open it up you should see (near the top) something like:-
Code:
[Theme]
; Windows 7 - IDS_THEME_DISPLAYNAME_AERO
DisplayName=Elmers Fav theme
To this, add a line:-
SetLogonBackground=1
So the [Theme] paragraph now reads something like:-
Code:
[Theme]
; Windows 7 - IDS_THEME_DISPLAYNAME_AERO
DisplayName=Elmers Fav Theme
SetLogonBackground=1
Now when you change back to your default, or favourite, theme, you'll get your own personalised login screen, not the Windows Default.
Sorry for the waffle and hope that that is of some use to you.