In the Adobe Photoshop image editing software, a variety of tools stand ready to help make your design process simpler. One of the collection of selection tools, the magnetic lasso, actually works by sensing the edges of an image or area and sticking to them like magnets. You still have to guide the tool around the area as you would tracing on a piece of paper, but the magnetic lasso helps you prepare an area to crop out and use in other designs, to swap backgrounds and to make other edits.
Start Adobe Photoshop. Click "File." Select "Open." Locate the image you want to crop with the magnetic lasso tool and double-click the file so the image opens on the canvas.
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Right-click the "Lasso" icon -- the third one from the top -- on the Tools pane. Choose "Magnetic Lasso Tool" from the fly-out menu.
Position your cursor along the outer edge of the object in the image that you want to crop. Click and hold down the left mouse button. Slowly drag your cursor along the edges to crop. The Magnetic Lasso Tool "sticks" to the edges as you drag.
Drag along the edges of the object to crop until you have come to where you started. The outlined area turns into an outline of dotted blinking lines.
Right-click inside the dotted lines and select "Layer via Cut."
Right-click the "Background" layer on the Layers palette on the right side of the screen. Click "Delete Layer." Click "Yes" at the warning window. You're left with just the cropped area outlined by the Magnetic Lasso Tool.