Using Adobe Photoshop CS, Part 1 - Working with Selections
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In our journey through life, we're always making selections. When we dress in the morning, we select what clothes to wear. When we order a meal at a restaurant, we select an entree from the menu. Selections are especially important in Photoshop due to the pixel-based nature of the program. With the exception of text and vector shapes, everything in Photoshop is just a mass of pixels. If you have a photograph with a blue sky, don't think of it as a sky that's colored blue, but rather many, many blue pixels that together form the image of a sky. If I want to change the sky to a different color, I can't just select the sky; I have to select all the individual pixels that form the sky. At a basic level, if I want to manipulate only part of my image, I need to isolate that part so that other parts of my image aren't affected (see Figure 5.18).
Figure 5.18 A file with one area of the image selected.
Note -Selections can also be called masks. When professionals used an airbrush to edit photographs in the past, they didn't want to accidentally affect other parts of the photo as they worked, so they cut masks (called friskets) that allowed them to use the airbrush on a specific part of the photo.
It may all sound a bit confusing, but as we go through the individual selection tools and the methods used to work with selections, everything will begin to make sense.
Marquee Selection Tools
In our basic introduction to making selections back in Chapter 4, we discussed the Marquee selection tools. They are used whenever you want to select a rectangular or elliptical range of pixels. For example, say you want to darken a rectangular area of a photo so that you can overlay some text. You would use the Rectangular Marquee tool to select an area that you will darken.
You have various options when using the Marquee tools:
Holding the Shift key while dragging will constrain the marquee area to a square or a circle.
Holding the (Option) [Alt] key while dragging will draw the marquee out from the center of where you clicked, rather than from the corner of where you clicked.
Holding the spacebar will "freeze" the marquee and let you position it anywhere in your image.
The options for the Marquee tool can be found in the Tool Options bar. By default, if you currently have a selection on your screen and then you draw a new marquee, you get a new selection and the previous marquee is discarded. You can change this behavior by choosing from the options Add, Subtract, or Intersect (see Figure 5.19). For example, if you draw your first selection, then click on the Add button, and then draw another marquee, both areas will become selected simultaneously. If your new marquee overlaps the previous one, they will be joined together to form a single larger selection.
Figure 5.19 Choosing marquee options from the Tool Options bar.
Tip -I personally find it tedious to have to navigate up to the Tool Options bar to specify Add, Subtract, or Intersect mode-so naturally I use the keyboard shortcuts. Holding the Shift key will add to your selection, holding (Option) [Alt] will subtract from your selection, and holding both Shift and Option (Alt) together will use the intersect mode.
Tip -Notice that the Marquee icon in the Tool Options bar is actually a pop-up menu button in itself. See the sidebar "Tool Options for Everyone," later in this section.
At times you may want to draw a marquee that is a specific size. Rather than guessing as you draw the marquee, you can choose one of the options from the Style pop-up in the Tool Options bar: Fixed Aspect Ratio (which will resample the file) and Fixed Size (see Figure 5.20). When either of these two options is chosen, you can enter a Width and Height value, and you'll notice that as you draw with the Marquee tool, your selection will be created or constrained to the dimensions you've specified.
Figure 5.20 Choosing the Fixed Aspect Ratio setting in the Tool Options bar.
After you've drawn your selection, you can move the selection around as you like by positioning your cursor anywhere inside the marquee, and then dragging it. You'll notice that only the selection itself moves, not the pixels that are inside it. To move the pixels themselves, switch to the Move tool or press and hold the (Command) [Ctrl] key before you start dragging the selection. To drag acopyof the selected pixels, press and hold the " (Ctrl)andthe (Option) [Alt] keys before you click and drag.
 This chapter is from Adobe Creative Suite, by Mordy Golding (Sams, 2003, ISBN: 0672325918). Check it out at your favorite bookstore today. Buy this book now.
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