I'm having troule with this png image...every time I open it the image has changed size. I'm trying to make a stencil and when I reopen it in photoshop the size is of the image size is correct but the placement has moved and it doesn't match up with the other half which has also changed. The canvas size is still correct. I need to use png or dds format for this to work in another program. Is there something I'm missing?...I need the background to be transparent.
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..