Understanding selection tools: Part I

Ask any two people how to highlight part of an image and you are bound to get a dozen answers. Like many aspects of computing, some of the answers are likely to be absurdly complicated, while others may be crude and ineffective. Among the responses, a simple question should emerge: what are you trying to select, and why? Different skills are needed to crop an image and to remove an unwanted person in the middle of a group.

This column is the first part of a series that focuses on various selection techniques. It will cover the overall approach, but some times you may need to consult your program’s manual for additional details — it should provide more detailed explanations of the steps involved.

The Marquee

Using the standard Marquee — also called the Selection tool — is a quick way to highlight part of an image. To use it, click the Marquee icon in your menu or toolbar (it is typically a rectangle with a dotted outline). Click at one point on the image and, with the left mouse button held down, drag out the area you want to highlight. Release the button when you are happy with the size. It is fairly simple and it’s not surprising most people stick to using it — even when there are better options (see here for a screenshot).

Most graphics programs let you choose from a list of geometric shapes for the Marquee, including squares, rectangles, circles and more. Some have very little practical value — how many times are you really going to need to use the octagonal selection feature in Paint Shop Pro? To make adjustments to the selection tool shape, head to the options palette or menu. In many programs, the options for a tool will only be visible once the tool has been selected. For example, you won’t see the Marquee’s options if you have highlighted the Text tool (you will only see the Text tool options).

Depending on your program, you can make a few other adjustments to the selection tool. Photoshop 7, Elements 2 and Paint Shop Pro 8 let you manually select the size of the Marquee. From the top toolbar choose the ‘Fixed Size’ option and drag the window to the position you want (in Paint Shop Pro, click the Custom Selection icon in the toolbar and manually enter the information).

Another option is feathering (see the Here’s How Graphics column in the October 2003 issue for more details) and some programs such as Paint Shop Pro 8 will give you the choice of Replace, Add or Remove. These three options are nothing new and can also be done in most programs without the need for special menu items (for details, see ‘Selection options’ below).

Now that you have selected part of an image, what are you going to do with it? If you want to crop your image to the selected areas, choose Image-Crop to Selection (Paint Shop Pro) or Image-Crop (Photoshop Elements and Photoshop). Likewise, Cut, Copy and Paste are straightforward. This is not the end your choices — there is still a lot more you can do.

By now you may have realised the limitation with the selection tool is that the shapes are quite basic. If you try to remove a person from your photographs, it is difficult to make a clean cut unless they have a square or octagonal head. Next month, this column will look at ways of selecting areas that are anything but geometric.

Selection options

Replace: The Replace option is fairly easy to use. If you don’t like the area you have highlighted, simply drag out a new one. This will clear your previous selection and use the new version.

Adding: You can select multiple areas of an image at the same time. Not only can they be different shapes and sizes, they can also overlap.

Draw your first Marquee, then hold down the key while making additional selections. Each new area will be added to the selection.

Subtracting: After making a selection, hold down the key while dagging out a new area. Any overlap between the two areas will be removed from the overall selection.

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Scott Mendham

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