If Preview recognizes a shape you draw it will choose that instead. There is also a Loupe tool which you can use to magnify an area of your image, just drag the green handle to decrease or the blue handle to increase magnification. Shape Tools: You can add rectangles, stars, and other shapes.
Press delete to make this part of the image transparent or tap Command+C to copy your selection, making it available in Clipboard. The more you drag the cursor the more of the image will be highlighted in red to show you have selected it. Just click the area you want to select and drag your cursor. When working with a PDF this becomes a rectangular selection tool. It also provides Lasso and Smart Lasso selection tools, on which more below. This tool is not available here when working with images.
