Photoshop.CS.Bible [Electronic resources] نسخه متنی

Chapter 7), but in case you're skipping around, here's the rundown: The eraser paints in the background color when used on the background layer. When applied to a layer, it erases pixels to reveal the layers below. The magic eraser works like the fill tool but in reverse. When you click with the magic eraser, you delete a range of similarly colored pixels. The background eraser, as its name implies, erases the background from an image and leaves the foreground intact — or at least, that's what happens if you use the tool correctly. Otherwise, it just erases everything.

The magic eraser

As I just mentioned, the magic eraser, found on the same flyout as the regular eraser, erases similarly colored pixels. If you're familiar with the magic wand, which I cover in Chapter 8, using the magic eraser is a cinch. The two tools operate virtually identically, except the wand selects and the magic eraser erases.

When you click a pixel with the magic eraser, Photoshop identifies a range of similarly colored pixels, just as it does with the magic wand. But instead of selecting the pixels, the magic eraser makes them transparent, as demonstrated in Figure 9-20. Bear in mind that in Photoshop, transparency requires a separate layer. So if the image consists of only the background, Photoshop automatically converts the background into a layer with nothing underneath. Hence we get the checkerboard pattern shown in the second example in the figure — transparency with nothing underneath.

Figure 9-20: To delete a homogeneously colored background, such as the sky in this picture, click inside it with the magic eraser (bottom).

You can further alter the performance of the magic eraser through the controls in the Options bar, shown in Figure 9-21 and described in the following list. Except for the Opacity value, these options work the same way as the options for the magic wand:

Figure 9-21: The magic eraser options are nearly identical to the options for the magic wand.

Tolerance: Just like the magic wand's Tolerance value, this one determines how similar a neighboring color has to be to the clicked color to be made transparent. A higher value affects more colors; a lower value affects fewer colors. (Remember, any change to the Tolerance value affects the next click you make; it does not affect the existing transparent area.)

Anti-aliased: To create a soft fringe around the outline of your transparent area, leave this option turned on. If you'd prefer a hard edge — as when using a very low Tolerance value, for example — turn this check box off.

Contiguous: Select this check box, and the magic eraser deletes contiguous colors only — that is, similar colors that touch each other. If you prefer to delete all pixels of a certain color — such as the background pixels in Figure 9-20 that are divided from the rest of the sky by the lion — turn the Contiguous check box off.

Use All Layers: When turned on, this check box tells Photoshop to factor in all visible layers when erasing pixels. The tool continues to erase pixels on only the active layer, but it erases them according to colors found across all layers.

Opacity: Lower this value to make the erased pixels translucent instead of transparent. Low values result in more subtle effects than high ones.

The more magical background eraser

The magic eraser is as simple to use as a hammer, and every bit as indelicate. It pounds away pixels, but it leaves lots of color fringes and shredded edges in its wake. You might as well select an area with the magic wand and press Backspace (Win) or Delete (Mac). The effect is the same.

The more capable, more scrupulous tool is the background eraser. As demonstrated in Figure 9-22, the background eraser deletes background pixels as you drag over them. (Again, if the image consists only of a background, Photoshop converts the background into a new layer to accommodate the transparency.) The tool is intelligent enough to erase background pixels and retain foreground pixels provided that — and here's the clincher — you keep the cross in the center of the eraser cursor squarely centered on a background color pixel. Move the cross over a foreground pixel, and the background eraser deletes foreground pixels as well. As Figure 9-23 demonstrates, it's the position of the cross that counts.

Figure 9-22: Drag around the edge of an image with the background eraser to erase the background but leave the foreground intact.

Figure 9-23: Keep the cross of the background eraser cursor over the background you want to erase (top). If you inadvertently move the cross over the foreground, the foreground gets erased (bottom).

You can also modify the performance of the background eraser using the Options bar controls, pictured in Figure 9-24. These options are a bit intimidating at first, but they're actually pretty easy to use:

Figure 9-24: The seemingly intimidating background eraser options are actually pretty intuitive.

Limits: Choose Contiguous from this pop-up menu, and the background eraser deletes colors inside the cursor as long as they are contiguous with the color immediately under the cross. To erase all similarly colored pixels, whether contiguous or not, select Discontiguous. One additional option, Find Edges, searches for edges as you brush and emphasizes them. Although interesting, Find Edges has a habit of producing halos and is rarely useful.

Tolerance: Raise the Tolerance value to erase more colors at a time; lower the value to erase fewer colors. Low Tolerance values are useful for erasing around tight and delicate details, such as hair.

Protect Foreground Color: Select this check box to prevent the current foreground color (by default, black) from ever being erased. Stupid, really, but there it is.

Sampling: This pop-up menu determines how the background eraser determines what it should and should not erase. The default setting, Continuous, tells the eraser to continuously reappraise which colors should be erased as you drag. If the background is pretty homogenous, you might prefer to use the Once option, which samples the background color when you first click and erases only that color throughout the drag. Select Background Swatch to erase only the current background color (by default, white).

The still more magical Extract command

Like the magic eraser and background eraser, the Extract command aims to separate — extract, if you will — an image element from its surroundings. After you draw a rough highlight around the subject you want to retain, Photoshop analyzes the situation and automatically deletes everything but the subject. In my estimation, though, Extract is only slightly more powerful than the background eraser and several times more complex. Some images respond very well to the command, others do not. That said, Extract can produce reasonably good results if you get the steps right. So take Extract for a test drive, as follows:

Choose Filter Extract. Or press Ctrl+Alt+X (z -Option-X on the Mac). Either way, Photoshop displays the large Extract window shown in Figure 9-25.

Figure 9-25: The Extract window serves as a miniature masking laboratory, complete with a toolbox and options.

Select the edge highlighter tool. Most likely, this tool is already active, but if not, press B to select it.

Outline the subject that you want to retain. In my case, I want to delete the background, so I traced around the lion, as shown in Figure 9-26. Be sure to either completely encircle the subject or, if the subject is partially cropped, trace all the way up against the outer boundaries of the photograph.

Figure 9-26: After tracing around the portion of the image you want to retain, click inside the outline with the fill tool.

As you trace, use the bracket keys, [ and ], to make the brush larger or smaller. When you work with brushes from 1 to 9 pixels in diameter, each press of [ or ] changes the brush size by 1 pixel. The increment of change gets larger as you increase the brush size.

If you make a mistake, press Ctrl+Z (z -Z on the Mac). You get only one Undo level here — you can undo and redo only your last stroke with the highlighter tool.

If you want to erase more of the highlight, drag over the botched region with the eraser tool (press E to access it from the keyboard) or press Alt (Option on the Mac) and drag with the edge highlighter tool. To delete the entire highlight and start over, press Alt+Backspace (Win) or Option-Delete (Mac).

Navigate as needed. If you can't see all of your image, you can access the hand tool by pressing the spacebar or clicking the hand tool icon. You can also zoom by pressing Ctrl+plus or Ctrl+minus (z -plus or z -minus on the Mac) or by using the zoom tool.

Select the fill tool. It's the one that looks like a paint bucket. To select the fill tool from the keyboard, press G, as you do to select the paint bucket in the regular Photoshop toolbox.

Click inside the subject of the image. The highlighted outline should fill with color. If the fill color spills outside the outline, your outline probably has a break. Press Ctrl+Z (z -Z on the Mac) to undo the fill and then scroll the image with the hand tool to find the break. Patch it with the edge highlighter and then click with the fill tool again.

Click the Preview button. Before you can apply your prospective mask, you need to preview it so you can gauge the finished effect, as in Figure 9-27.

Figure 9-27: Click the Preview button to gauge the appearance of the final masked image.

Edit the mask as needed. You have several tools at your disposal. These tools are labeled in Figure 9-27, and you can read about them in the list following these steps.

Click the OK button to delete the masked portion of the image. If the image consisted of only a background, Photoshop converts it into a separate layer. You can then use the move tool to drag the layer against a different background. In Figure 9-28, I set my lion against an Italian landscape. The composite isn't perfect, but it's not half bad for five to ten minutes of work.

Figure 9-28: I believe this particular lion is stuffed, but even a dead creature may enjoy a change in its diorama.

After you exit the Extract window, fix any problems using the background eraser and history brush. Use the background eraser to erase stray pixels that you wish the Extract command had deleted. Use the history brush to restore details that you wish the Extract command hadn't deleted.

Back in Step 10, I alluded to ways that you can refine the mask in the Extract dialog box. You can use the following techniques to touch up the mask before clicking OK to create it:

Drag with the cleanup tool (C) to change the opacity of the mask. Press the number keys to adjust the pressure of the tool and thus alter the amount of opacity that the tool subtracts. To erase to full transparency, press 0, as you do when working with the eraser on a layer. Press 9 for 90 percent transparency, 8 for 80 percent, and so on. Alt-drag (Win) or Option-drag (Mac) to add opacity.

Drag along the boundaries of the mask with the edge touchup tool (T) to sharpen the mask edges. If the boundary between mask and subject isn't well defined, dragging with this tool adds opacity to the subject and removes it from the mask. In other words, it turns soft, feathery edges into crisp, clearly defined edges. Again, you can press the number keys to adjust the impact of the tool.

Raise the Smooth value to remove stray pixels from the mask. A high value smoothes out the edges around the image and fills in holes. Basically, if your edges are a big mess, give this option a try.

Drag with the edge highlighter or eraser tool to edit the mask boundary. When you select either tool, the original mask highlight reappears, and the tools work as they do when you initially draw the highlight. After you adjust the highlight, Shift-click inside it to redraw and preview the adjusted mask.

Choose an option from the Show pop-up menu to toggle between the original highlight and the extracted image preview. You can press X to toggle between the two views without bothering with the pop-up menu.

That's 99 percent of what you need to know about the Extract command. For those of you who care to learn the other 1 percent, here's a quick rundown of the remaining options that appear along the right side of the Extract window:

Highlight, Fill: Use these pop-up menus to change the highlighter and fill colors. It doesn't matter what colors you use, as long as they show up well against the image.

PhotoshopTextured Image: If your image is highly textured, try turning on this check box. Much like the Smooth option, it helps smooth out jagged edges around the image.

Channel: Advanced users may prefer to prepare the highlighter work by tracing around the image inside an independent mask channel, which you can create in the Channels palette before choosing the Extract command. Then load the mask by selecting it from the Channel pop-up menu. You can further modify the highlight using the edge highlighter and eraser tools. One weirdness: When loading a mask, black in the mask channel represents the highlighted area and white represents the nonhighlighted area. Strikes me as upside-down, but that's how it goes.

Force Foreground: If the subject of your image is predominantly a single color, select Force Foreground and use the eyedropper to sample the color in the image that you want to preserve. (Alternatively, you can define the color using the Color swatch, but it's much more work.) Then use the edge highlighter tool to paint over all occurrences of the foreground color. (Note that this check box is an alternative to the fill tool. When Force Foreground is selected, the fill tool is dimmed.)

Display: You don't have to preview the image against the transparent checkerboard background. You can also view it against white (White Matte) or some other color. Or you can view it as a mask, where white represents the opaque area and black the transparent area. (Ironically, you can't export the extraction as a mask — go figure.)

Show Highlight, Show Fill: Use these check boxes to hide and show the highlight and fill colors.

Using the Color Range command

Another convenient method for creating a mask is the Color Range command in the Select menu. This command enables you to generate selections based on color ranges. Use the familiar eyedropper cursor to specify colors that should be considered for selection and colors that you want to rule out. The Color Range command is a lot like the magic wand tool, except it enables you to select colors with more precision and to change the tolerance of the selection on-the-fly.

When you choose Select Color Range, Photoshop displays the Color Range dialog box shown in Figure 9-29. Like the magic wand with the Contiguous option turned off, Color Range selects areas of related color all across the image, whether or not the colors are immediate neighbors. Click in the image window to select and deselect colors, as you do with the wand. But rather than adjusting a Tolerance value before you use the tool, you adjust a Fuzziness option any old time you like. Photoshop dynamically updates the selection according to the new value. Think of Color Range as the magic wand on steroids.

Figure 9-29: The Color Range dialog box enables you to generate a mask by dragging with the eyedropper tool and adjusting the Fuzziness option.

When you move your cursor outside the Color Range dialog box, it changes to an eyedropper. Click to specify the color on which you want to base the selection — I call this the base color — as if you were using the magic wand. Or click inside the preview, labeled in Figure 9-29. In either case, the preview updates to show the resulting mask.

You can also do the following:

Add colors to the selection: To add base colors to the selection, select the add color tool in the Color Range dialog box and click inside the image window or preview. You can access the tool while the standard eyedropper is selected by Shift-clicking (just as you Shift-click with the magic wand to add colors to a selection). You can even Shift-drag with the eyedropper to add multiple colors in a single pass, something you can't do with the magic wand.

Remove colors from the selection: To remove base colors from the selection, click with the remove color tool or Alt-click (Option-click on the Mac) with the eyedropper. You can also drag or Alt-drag (Option-drag on the Mac) to remove many colors at a time.

Adjust the Fuzziness value: This option resembles the magic wand's Tolerance value because it determines the range of colors to be selected beyond the ones you click. Raise the Fuzziness value to expand the selected area; lower the value to contract the selection. A value of 0 selects only the clicked color. Unlike changes to Tolerance, however, changing the Fuzziness value adjusts the selection on-the-fly; no repeat clicking is required, as it is with the wand tool.

Fuzziness and Tolerance also differ in the kind of selection outlines they generate. Tolerance entirely selects all colors within the specified range and adds antialiased edges. If the selection were a mask, most of it would be white with a few gray pixels around the perimeter. By contrast, Fuzziness entirely selects only the colors you click and Shift-click, and it partially selects the other colors in the range. That's why most of the mask is expressed in shades of gray. The light grays in the mask represent the most similar colors; the dark grays represent the least similar pixels that still fall within the Fuzziness range. The result is a tapering, gradual selection, much more likely to produce natural results.

Reverse the selection: Select the Invert check box to reverse the selection, changing black to white and white to black. As when using the magic wand, it may be easier to isolate the area you don't want to select than the area you do want to select. When you encounter such a situation, select Invert.

Toggle the preview area: Use the two radio buttons below the preview area to control the preview's contents. If you select the first option, Selection, you see the mask that will be generated when you press Enter (Win) or Return (Mac). If you select Image, the preview shows the image.

Control the contents of the image window: The Selection Preview pop-up menu at the bottom of the dialog box enables you to change what you see in the image window. Leave the option set to None — the default setting — to view the image normally in the image window. Select Grayscale to see the mask on its own. Select Quick Mask to see the mask and image together. Select Black Matte or White Matte to see what the selection would look like against a black or white background.

Although they may sound weird, the Matte options enable you to get an accurate picture of how the selected image will mesh with a different background. Figure 9-30 shows an original image at the top left with the grayscale mask on the right. The mask calls for the shadows in the disc, fingers, and wrist to be selected, with the highlights deselected. The two Matte views help you see how this particular selection looks against two backgrounds as different as night and day. Use the Fuzziness option in combination with Black Matte or White Matte to come up with a softness setting that will ensure a smooth transition.

Figure 9-30: The options in the Selection Preview pop-up menu change the way the Color Range command previews the selection in the image window.

Select by predefined colors: Choose an option from the Select pop-up menu at the top of the dialog box to specify the means of selecting a base color. If you choose any option besides Sampled Colors, the Fuzziness option and eyedropper tools become dimmed to show that they are no longer operable. Instead, Photoshop selects colors based on their relationship to a predefined color. For example, if you select Red, the program entirely selects red and partially selects other colors based on the amount of red they contain. Colors composed exclusively of blue and green are not selected.

The most useful option in this pop-up menu is Out of Gamut, which selects all the colors in an RGB or Lab image that fall outside the CMYK color space. You can use this option to select and modify the out-of-gamut colors before converting an image to CMYK.

Load and save settings: Click the Save button to save the current settings to disk. Click Load to open a saved settings file. To use a settings file on a PC, it must end in the .axt extension.

After you define the mask to your satisfaction, click OK or press Enter or Return to generate the selection outline. Although the Color Range command is more flexible than the magic wand, you can no more expect it to generate perfect selections than any other automated tool. After Photoshop draws the selection outline, therefore, you'll probably want to switch to the quick mask mode and paint and edit the mask to taste.

If you learn nothing else about the Color Range dialog box, at least learn to use the Fuzziness option and the eyedropper tools. Basically, you can approach these options in two ways. If you want to create a diffused selection with gradual edges, set the Fuzziness option to a high value — 60 or more — and click and Shift-click two or three times with the eyedropper. To create a more precise selection, enter a Fuzziness of 40 or lower and Shift-drag and Alt-drag (Option-drag on the Mac) with the eyedropper until you get the exact colors you want.

Figure 9-31 shows some sample results. To create the left images, I clicked with the eyedropper tool once in the disc and set the Fuzziness value to 40. To create the right images, I raised the Fuzziness value to 180; then I clicked, Shift-clicked, and Alt-clicked with the eyedropper to lift exactly the colors I wanted. The top examples show the effects of filling the selections with white. In the two bottom examples, I copied the selections and pasted them against an identical cloud background. In all four cases, the higher Fuzziness value yields more generalized and softer results; the lower value produces a more exact but harsher selection.

Figure 9-31: After creating two selections with the Color Range command — one with a low Fuzziness value (left) and one with a high one (right) — I alternately filled the selections with white (top) and pasted them against a different background (bottom).

A few helpful Color Range hints

You also can add to or subtract from an existing selection using the Color Range command. Press Shift when choosing Select Color Range to add to a selection. Press Alt (Win) or Option (Mac) when choosing Color Range to subtract from a selection.

If you get hopelessly lost when creating your selection and you can't figure out what to select and what to deselect, click with the eyedropper tool to start over. This clears all the colors from the selection except the one you click. Or you can press Alt (Option on the Mac) to change the Cancel button to a Reset button, which returns the settings in the dialog box to those in force when you first chose Select Color Range.