Selections are arguably the most important part of any Photoshop workflow. They allow us to precisely target specific objects or regions of the photo, so that we can apply edits to only those areas (or mask only those areas). Photoshop provides several tools for creating selections (or generating masks); each one is specialized for selecting a particular type of shape or range of tone and color.
One of the most useful selection tools is the Polygonal Lasso, which allows you to precisely place marquee segments along the edges of manmade objects or other straight-edged subjects.
For the image below, it might be useful to apply edits to only the pixels seen within the boundary of the window frame. However because of the geometric distortions here, it’s not possible to use the Rectangular Marquee. The selection produced only fits one part of the window, while overlapping the shutters in another.
To get around this problem, we can use the Polygonal Lasso tool. Let’s take a look:
To select the Polygonal Lasso, press the L key. This might choose the standard Lasso tool by default. It looks like this.
To switch to the Polygonal Lasso, hold down the Shift key and then tap L until you see this icon.
Take a look at your image and decide where you want to start your polygonal selection, then zoom in so that you can see the corner of that edge clearly.
Move the cursor above the corner and click one time. Next move the cursor along the edge; as you move it, a line is drawn, originating from the corner. As you move the stylus or mouse the length and direction of the line changes.
Move the cursor so that the line is placed exactly along the edge of your subject. When you reach the next corner, click one time again. This will fix the line you’ve drawn in place and allow you to create the next one; each new segment remains connected to the prior one. As you move the cursor over the boundary of the window, the image should scroll, revealing hidden areas.
Note: If you want to start over, tap Escape and all of the segments will be removed.
Continue on to the next corner, repeating the process of following the edge and then clicking on each corner, until you’ve worked your way back to the original corner where you started the selection.
Ensuring that you’re still following the final edge, move the cursor over the spot where you started. When you do this, the Polygonal Lasso cursor will display a “circle” to indicate that you can “close the loop” by clicking on this spot. When you do, you will create a polygon selection!