Lesson C: Lasso & Polygonal Lasso

Now let’s open an arresting image of a stop sign: “C polygonal lasso.psd.” (The bad puns are free.) We’ll be changing the color in the stop sign from red to green. First, we’ll experiment with the tools under discussion.

The Lasso Tool

If you tap the L key, you find yourself wielding the Lasso tool—or one of them. There are two worth looking at: the regular Lasso tool and the Polygonal Lasso tool. Both are very easy to use. The first is not meant for creating precise, intricate selections but rather loose, approximate ones.

• Activate the Lasso tool (tap the L key).
• Press and drag a loop around a part of the image (it doesn’t matter where, as we won’t use this tool in the end).
• When you release the mouse, you’ve got a selection in that shape.
• Deselect by either choosing Select > Deselect or using the shortcut ⌘-D/Ctrl-D.
• Now, make a U-shape with the Lasso tool, releasing the mouse some distance from where you started dragging. Photoshop will close the shape for you with a straight line.
• Deselect by either choosing Select > Deselect or using the shortcut ⌘-D/Ctrl-D.

The Polygonal Lasso Tool

Now let’s try a more interesting tool. We’ll do one or two practice rounds, then we’ll make the selection we need.

• Activate the Polygonal Lasso tool by right-clicking the Lasso tool and choosing the second tool in that slot. You may also use shift-L to cycle through the lasso tools.
• This time, don’t drag, but click repeatedly around an area of the image. Each click tacks down a vertex of the polygon you’re creating. Click where you want each vertex to be.
• Work your way around a part of the image, then click back where you started.

While you’re creating a selection, there is no selection yet. So if you start this process unintentionally, the Deselect command or shortcut will not help you. You have to tap the escape key to stop this tool. Or you can complete the task.

There are three ways to finish a selection with this tool:

• Work your way back to the starting point and make your last click there.
• Double-click the last vertex you set. This sets that vertex and closes the selection, and is the most efficient method. See the illustration that follows.
• From the position of the last vertex, press the Enter key instead of clicking. This creates that vertex and closes the selection. No one does this.

• Hold down the Z key to zoom in to the stop sign so you can more easily create the selection.
• For each click with the Polygonal Lasso tool, locate the tip of the cursor in the white band between the edge of the sign and the red part of it. I started in the upper right and proceeded counterclockwise.
• When the cursor is at what would be the last vertex, double-click. This closes the shape and gives you marching ants.
• If you made a significant mistake, use it as an opportunity to practice: deselect by choosing Select > Deselect or using the shortcut ⌘-D/Ctrl-D, then try again.

With the completed selection, let’s make that adjustment.

• With the marquee in place, create a Hue/Saturation adjustment layer by clicking its icon in the Adjustments panel.
• Move the Hue slider to the right until the stop sign’s color is green.
• Admire your work for a while, then save the file and close it.