This is a quick and easy way to extract an image from Photoshop CS4– First your going to open your image right click on your background layer and select duplicate layer. Now you should have two layers exactly the same.
On one of the layers use your selection tool to select what area you want to extract. Don’t worry if it selects a little beyond what you are working on we can clean that up in a minute.
With you mask tool open (Windows->Masks) click on Add A Pixel Mask
Turn off your first layer so you only see the layer you are working with. Use your eraser tool to erase anything that is obviously not part of the image you want extracted. Now look for the feather tool on your Mask editor and feather the edges a little bit.
Now you can work on either the background layer or the extracted layer.