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Using Photoshop Selection Tools
Part 3: Selecting with Photoshop's Lasso and Polygonal Lasso Tools - Creating a Triangle
by Shirley E. Kaiser, M.A., SKDesigns
Published 1999. Updated March, 2006. Copyright © 2001-2021, Shirley E. Kaiser, M.A., SKDesigns. All rights reserved. Published at websitetips.com with permission.
This Photoshop tutorial will help show you the basics of using the Lasso tool, one of Adobe Photoshop's helpful selecting tools. You'll find instructions for Photoshop CS2 and also for Photoshop 5.5.
Originally written when Photoshop 5.5 was new, updated March 2006 for Photoshop CS2 - so you'll find screenshots for both versions where Photoshop's interface differs between these versions.
On this page:
What are the Lasso Tools and What Can they Do?
Photoshop's Lasso tools are designed for freehand selecting, and will create straight edge and freehand selection lines. Among its many uses, it is often used for carefully selecting certain elements of an image or creating certain shapes. To help learn how to work with the Lasso tools, below is a tutorial to create a triangle border selection using the Lasso tool (for 5.5) 
and the Polygonal Lasso tool (for CS2). 
Photoshop's Lasso Options (Lasso Options palette in 5.5) contains settings for feathering and anti-aliasing, as shown in Example 1.1a (CS2) and Example 1.1b (5.5) below. For the typical Web graphic, you'll probably use the Anti-aliased setting, especially for rounded or curved edges; however, turn off anti-aliasing (uncheck the box) if you need a crisp horizontal or vertical line selection.
Ex. 1.1a: Lasso Tools Options
Photoshop CS2
Ex. 1.1b: Lasso Tools, Lasso Tools Options Palette
Photoshop 5.5
For retouching, sometimes I will use the Lasso tool with a feathered edge using the Feather setting to copy a selection and then paste it as a new layer over a blemish, moving it around as needed. The feathering can provide a softer edge to provide a more seamless integration in a varied color graphic. The Rubber Stamp tool and the newer Healing Brush tool can also be used for this, too.
The Feather setting used depends on the application, of course. Feathering probably wouldn't be needed to cover a blemish on a solid color, for example. Experimenting with a variety of settings to see what it will do is a great way to get an understanding of this very helpful tool.
TIP:
Tip 1: What to do when you make a mistake. Tips 4 and 5 below provide ways of altering what you've done. However, if you'd like to start over with your selection, from the drop-down menu, click on Select>Deselect. Then try again.
Tip 2: Zoom in or out. It can be quite helpful for accuracy to zoom in on your image while using the lasso tool to do selecting. From the drop-down menu select View>Zoom In or View>Zoom Out. Or with your keyboard, press CTRL+ (Zoom In) or CTRL- (Zoom Out).
Tip 3: Straight lines. For Photoshop CS2 using the Polygonal Lasso tool, click on the corner points only - don't drag. To complete the selection, click on the starting point to close the shape.
For Photoshop 5.5, hold down the ALT key in Windows (the Option key on a MAC), click the Lasso tool, then drag for each straight line segment, clicking where desired to change direction for the line.
Tip 4: Erasing segments. You can erase segments of the line by holding down the DEL (delete) key until the amount you wish is erased. It deletes fairly quickly, so watch out! <grin>
Tip 5: Adding and subtracting selections. Holding down the SHIFT key while you're selecting an area adds to the current selection. Holding down the ALT key (Options key for MACs) subtracts from the selection.
Tip 6: Patience. It will undoubtedly take some practice with the Lasso tools to gain the accuracy you'll need for certain selecting jobs. So be patient with yourself as you begin working with these helpful selecting tools.
Straight-Edged Border Selection, aka Creating a Triangle Shape with the Lasso Tools
To demonstrate this, let's create a triangle shape using one of Photoshop's Lasso tools. We'll then either fill the inside of the triangle with the Paintbucket or with the Edit>Fill command, use Edit>Stroke for an outlined triangle, OR create a filled and outlined triangle, as you'll see below.
Important points:
- For Photoshop CS2, select the Polygonal Lasso tool on the toolbox, as shown in Example 1.1a above.
- For Photoshop 5.5, select the Lasso tool on the toolbox, as shown in Example 1.1b above.
- Within the Lasso Options settings, make sure the settings are '0' for feather and that the Anti-aliased checkbox is checked, as shown in Examples 1.1a (CS2) and 1.1b (5.5).
- For Photoshop 5.5, hold the ALT key down in Windows (the Option key on a MAC) for creating the entire triangle, which is made with 3 straight line segments.
OK, let's go.
- Click your mouse where you want to begin the triangle. I started at the top in Step 1 shown below.
Step 1 - Photoshop CS2
Step 1 - Photoshop 5.5 - For Photoshop CS2, then click on the next corner point - there's no need to drag the tool to the next corner.
For Photoshop 5.5, then release and drag the tool to the next corner, clicking at the corner. Then release and drag the tool to the second corner, clicking the mouse again, as shown in Step 2 below. You might have noticed that the Lasso tool turned into the Polygonal Lasso tool.
Step 2 - For Photoshop CS2, then click on the next corner, which will be where you started, being certain to meet (thus adjoining) the line, clicking the mouse, as shown in Step 3 below.
For Photoshop 5.5, then drag the tool to the next corner, which will be where you started, being certain to meet (thus adjoining) the line, clicking the mouse, as shown in Step 3 below.
Step 3 - Release the click. Now you should have a triangle selection, something like the example shown below. You may have also noticed that if the selection lines initially looked jagged as you did your selecting that Photoshop has straightened the selection lines from point to point.
Step 4 - After choosing a foreground color to fill your triangle, you're now ready to:
fill the inside of the triangle using Edit>Fill from the drop-down menu -OR- the Paintbucket tool,
Fill with Edit>Fill or
Paintbucket tool-OR- create an outlined triangle using Edit>Stroke from the drop-down menu,
Outlined Triangle using Edit>Stroke-OR- both fill and outline.
TIP:
If you wish to have an outlined and filled triangle, in the Stroke pop-up box, click the Location: Outside radio button. If you use Inside or Center, the line may not show up or appear inconsistent. See my tutorial, Creating Outlined Shapes with Photoshop's Marquee Tool for screenshots of the Stroke pop-up box and further instructions if needed.
- That's it! Now you're ready to save your image and use the triangle if you wish.
- Try creating more shapes and explore what this tool will do. Experimenting and playing around with these tools will go a long way with learning how to use them effectively.
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