My first experience with changing backgrounds was on a computer was on a 486 computer using a program called Adobe PhotoDelux. Most of what editing of photos I do now I use a program called PhotoFiltre - http://photofiltre.free.fr/. One thing I haven't figured out how to do in this program is to change backgrounds. This program don't seem to have any layer options. So I resort to another one of my classic programs called Adobe Photoshop 7.
One of the problems I have with changing backgrounds is I don't do it enough to remember what steps I need to take to change my backgrounds. I will not achieve any awards for my memory. So I confess this is more of a guide for me but you all are free to use it to. :-) I can't confirm or deny if this is the same procedure for the newer versions of Photoshop, can someone please confirm or deny in the comments?
I have the program open and I'm going to use two pieces of clip art for this example. I'm going to take this little dog and place him on with the partying cats. So open both pictures that you want to alter.
We need to go to the layers section and duplicate the layer. Click on the segment across with the word background on it and drag it down to the second last icon and let go. If done properly you will now have two layers.
Click on the lock symbol in the new layer. Some on-line guides suggested to click once of the lock symbol but in my case a double click is required.
Then a New Layer windows will open. In my case I'll keep it at it's default settings.
Now you will have two layers listed. One named Background the other in my case Layer 0. On the one labeled Background or in my situation Background copy click on the eyeball symbol to hide that layer.
Now the fun part begin. Erasing the background, for my example the dog. There are different ways to do this job. I prefer to use the eraser tool because most times the backgrounds in the pictures I have done are with real people and the backrounds are a little more complex. So click on the eraser tool and start erasing the background that you want changed.
Use the eraser tool to erase the background. Think of it as colouring. Becareful around the edges. Hold down the Ctrl key and keep clicking on the + (plus) key to zoom in or the - (minus or dash) key to zoom out. The end result will have a gray checkerboard pattern around it. So far so good.
When erasing you can adjust the size of the brush (cursor) by clicking in the top left hand corner on the little inverted triangle and then either adjusting the slider or clicking on a larger size in the section just under.
Once all erasing is done click on the Move Tool. Usually the second icon, top of tools menu, looks like a arrow pointing to the top left corner and a cross in the bottom right.
Now here is where I originally couldn't get it to work at first. Just click on the subject in question , my doggy, hold down and drag it to the new background. I found a guide online that said to drag and press Enter. In my case it wouldn't work at all so I just decieded to try the dragging alone. That did it. Depending on your version of Photoshop, try it one way if it don't work try the other.
Now you see I have the dog on the Happy Birthday background but he/she is a little to big, so by pressing Ctrl + T you'll notice a square outline around your subject. By clicking and dragging one of the little square points on the frame you can make it bigger or smaller. In my case I want to make it smaller so I'll click on the outside corner one and push it in towards the center. Press Enter when finished. Other than resizing you can drag it around to the position that you want.
The end result.
Fianlly, save your picture. You'll probably want to chose .jpg format for websites, Facebook or emails. I also like to save a copy in it's native format of .psd for future potential edits.