The Select MenuIf making selections using lassos and marquees, then saving or loading them, were all there was to selecting in Photoshop, life would be simpler but duller. Fortunately for us, there are many more things you can do with selections, and they allwell, almost allhelp immeasurably in the production process.You can find each additional selection feature under the Select menu: Grow, Similar, Color Range, and Modify. Let's explore each of these and how they can speed up your work. GrowEarlier in the chapter, when we were talking about the Magic Wand tool, we discussed the concept of tolerance. This value tells Photoshop how much brighter or darker a pixel (or each color channel that defines a pixel) can be and still be included in the selection.Let's say you're trying to select an apple using the Magic Wand tool with a tolerance of 24. After clicking once, perhaps only half of the apple is selected; the other half is slightly shaded and falls outside the tolerance range. You could deselect, change the tolerance, and click again. However, it's much faster to select Grow from the Select menu.When you choose Grow, Photoshop selects additional pixels according to the following criteria.
In other words, Photoshop tries its hardest to spread your selection in every direction, but only in similar colors. However, it doesn't always work the way you'd want. In fact, sometimes it works very oddly indeed.For instance, if you select a pure red area (made of 255 red, and no blue or green), and a pure green area (made of 255 green, and no red or blue), then select Grow, Photoshop selects every adjacent pixel that has any red or green in it, as long as the blue channel is not out of tolerance's range. That means that it'll pick out dark browns, lime greens, oranges, and so oneven if you set a really small tolerance level (see Figure 8-20). Figure 8-20. Anomalies with the Grow commandSimilarThe Grow feature only selects contiguous areas of your image. If you're trying to select the same color throughout an image, you may click and drag and grow yourself into a frenzy before you're done. Choosing Similar from the Select menu does the same thing as choosing Grow, but it chooses pixels from throughout the entire image (see Figure 8-21). Figure 8-21. The Similar commandColor RangeOne of the problems with Similar and Grow is that you rarely know what you're going to end up with. On the other hand, Color Range lets you make color-based selections interactively, and shows you exactly which pixels will be selected. But there's one other advantage of Color Range over the Magic Wand features (we think of Similar and Grow as extensions of the Magic Wand).The Magic Wandbased features either select a pixel or they don't (the exception is anti-aliasing around the edges of selections, which only partially selects pixels there). Color Range, however, fully selects only a few pixels and partially selects a lot of pixels (see Figure 8-22). This can be incredibly helpful when you're trying to tease a good selection mask out of the contents of an image. Figure 8-22. Magic Wand versus Color Range[View full size image] Adding and deleting colorsWhen you open Color Range, Photoshop creates a selection based on your foreground color. Then you can use the eyedropper tools to add or delete colors in the image (or, better yet, hold down the Shift key to get the Add Color to Mask eyedropper, or the Option key to get the Remove Color from Mask eyedropper). Note that you can always scroll or magnify an area in the image. You can even select colors from any other open image. The Fuzziness factorThe Fuzziness slider in the Color Range dialog box is not the same as the Tolerance field on the Magic Wand Options bar. As we said earlier, pixels that fall within the tolerance value are either fully selected or not; pixels that fall on the border between the selected and unselected areas may be partially selected, but those are only border pixels. Color Range uses the Fuzziness value to determine not only whether a pixel should be included, but also how selected it should be. We're not going to get into the hard-core math (you don't need to know it, and we're not entirely sure of it ourselves), but Figure 8-23 should give you a pretty good idea of how fuzziness works. Figure 8-23. Fuzziness versus sample points for Color Range[View full size image] Canned ColorsInstead of creating a selection mask with the eyedroppers, you can let Photoshop select all the reds, or all the blues, or yellows, or any other primary color, by choosing the color in the Select popup menu (see Figure 8-24). The greater the difference between the color you choose and the other primaries, the more the pixel is selected. (To get really tweaky for a moment: The percentage the pixel is selected is the percentage difference between the color you choose and the primary color with the next highest value.) Figure 8-24. Color Range dialog box
Selection PreviewThe last area to pay attention to in the Color Range dialog box is the Selection Preview popup menu. When you select anything other than None (the default) from this menu, Photoshop previews the Color Range selection mask.The first choice, Grayscale, shows you what the selection mask would look like if you saved it as a separate channel. The second and third choices, Black Matte and White Matte, are the equivalent of copying the selected pixels out and pasting them on a black or white background. This is great for seeing how well you're capturing edge pixels. The last choice, Quick Mask, is the same thing as clicking OK and immediately switching into Quick Mask mode.Because the Selection Preview can slow you down, we recommend turning it on only when you need to, then turning around and switching back to None. It can be really helpful in making sure you're selecting everything you want, but it can also be a drag on productivity.Tip: Changing Quick Mask OptionsIf you're a hard-core Color Range user, you may one day have the strange desire to change your Quick Mask options settings while the Color Range dialog box is open. You can do it (believe it or not). Hold down the Option key while selecting Quick Mask from the Selection Preview popup menu. Don't say we don't strive to give you every last tip!Tip: Forget the Color Range Radio ButtonsIf you frequently use the Image and Selection radio buttons in the Color Range dialog box, stop! Instead, press the Command or Control keyeither one works on the Macon your keyboard. This toggles between the Selection and Image Previews much faster than you can click buttons. This is sometimes helpful if you need a quick reality check as to what's selected and what's not. ModifyWhen you think of the most important part of your selection, what do you think of? If you answer, "what's selected," you're wrong. No matter what you have selected in your image, the most important part of the selection is the boundary or edge. This is where the tire hits the road, where the money slaps the table, where the invoice smacks the client. No matter what you do with the selectionwhether you copy and paste it, paint within it, or whateverthe quality of your edge determines how effective your effect will be.When making a precise selection, you often need to make subtle adjustments to the boundaries of the selection. The four menu items on the Modify submenu under the Select menuBorder, Smooth, Expand, and Contractfocus entirely on this task. BorderPolice officers of the world take note: There's a faster way to get a doughnut than driving down to the local Circle K. Draw a circle using the Marquee tool, then select Border from the Modify submenu under the Select menu. You can even specify how thick you want your doughnut (in pixels, of course). Border transforms the single line (the circle) into two lines (see Figure 8-25). Figure 8-25. Border
You can save this selection and delete one or both of the other alpha channels you saved. Note that you don't have to expand and contract the selection; this method also lets you choose to only contract or expand.Note that we also discuss another way to make borders (edge masks) in Chapter 9, Sharpness, Detail, and Noise Reduction. SmoothThe problem with making selections with the Lasso tool is that you often get very jaggy selection lines; the corners are too sharp, the curves are too bumpy. You can smooth these out by selecting Smooth from the Modify submenu under the Select menu. Like most selection operations in Photoshop, this actually runs a convolution filter over the selection maskin this case, the Median filter. That is, selecting Smooth is exactly the same thing as switching to Quick Mask mode and choosing the Median filter.Smooth has little or no effect on straight lines or smooth curves. But it has a drastic effect on corners and jaggy lines (see Figure 8-26). Smooth (or the Median filter, depending on which way you look at it) looks at each pixel in your selection, then looks at the pixels surrounding it (the number of pixels it looks at depends on the Radius value you choose in the Smooth dialog box). If more than half the pixels around it are selected, then the pixel remains selected. If fewer than half are selected, the pixel becomes deselected. Figure 8-26. SmoothExpand/ContractThe Expand and Contract features are two of the most useful selection modifiers. They let you enlarge or reduce the size of the selection. This is just like spreading or choking colors in trapping (if you don't know about trapping, don't worry; it's not relevant here).Once again, these modifiers are simply applying filters to the black-and-white mask equivalent of your selection. Choosing Expand is the same as applying the Maximum filter to the mask; choosing Contract is the same as applying the Minimum filter (see Figure 8-27). Figure 8-27. Expand and Contract
What's nice about this tip is that it's a very gentle method of expanding or contracting the selection. Instead of "Wham! Move one pixel over," you can say, "Make this selection slightly bigger or smaller." |