The scissor tool (selects shapes from images) can be a confusing tool at first, but once you get the hang of it, it's great for extracting objects from your photos.
Step 1: Open your image
Go ahead and open up the image you want to try this on. I'm going to use this image:
Step 2: Start clicking
Select the Scissor tool (Shortcut: i). Next, click on the edge of your shape.
Then keep clicking at regular intervals on the edge, making your way around the perimeter of your shape.
Step 3: Finalize Selection
Once you have finished settings points around your shape, you need to make it into a selection so you can work with it. Before you do this though, you might want to go into the Scissors tool options and check Feather Edges to create a smooth selection:
Now, click on the first point you made. The last point should be connected your first point at this step. Finally, just click inside the perimeter to turn it into a selection:
Now that you've got your selection, you can do anything you want! Have fun!
