I can suggest you one work around that may work for you.
In PSE you can create a Blank File that can have a white or Transparent background as you want to.
As per you posted you have the image size beforehand.
So I will suggest you to create a blank file with transparent background of the same size as of your image size and then place your image on new created transparent file.
To create a new blank file :- steps
1. Go to File -> New -> Blank File or you can hit Command + N (for MAC) / ctrl + N for windows.
you will have below window ...
After creating a new blank file now you can place your png image.
Hope it would work fine for you..
1 person found this helpful
Once you place the image you can use the move tool to put where it needs to be. Also, when the move tool is active and the new material is selected there, you can nudge it with the arrow keys.
Perfect...just Sam and Barbara. That makes it possible to manipulate the whole image and not lose the orginal quality. Thanks so much