Polygon Lasso Tool
The polygon lasso tool creates a selection that is bounded by straight lines. You can select the polygon lasso tool from the toolbar on the left of the online image editor or by going to the polygon lasso
Drawing Selections with the Polygon Lasso
To create a polygon lasso selection click from point to point to create a polygon around the area you want to select. You can also click and follow the edges of objects in the image that you wish to extract. A straight line is created between every click point. To complete and close the selection double click in the work area at any point. The selection closes on the first clicked point of the selection.
There are four modes that determine how the newly drawn selection is added to the to the image and how it interacts with a selection that already present.
New - The new selection will replace any active selection in the image.
Union - The new selection will be combined with the old selection.
Subtract - The area covered by the new selection will be subtracted from the old selection.
Intersection - A selection will be made from the intersecting region of the old selection and the new selection..
constrains the rectangular selection to the selected aspect ratio e.g 4:3.
The amount of pixels to be moved when the arrow key is pressed.
Learn more about using selections