Merging into the background
If you want to merge the edges of your image into the background, there is a very simple way to do the same in the color palette make the background color (the color you want).
Selections > Select All
Selections > Modify > Contract (try some 10 or 15 pixels)
Selections > Modify > Feather (also some 10 or 15 pixels)
Selections > Invert
Hit the delete key, repeat if necessary.
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