Working with Multiple Layers
Working with Multiple LayersYou have seen how to create, move, and remove layers, but the hour still hasn't really addressed the question of what they're good for. You will use layers in many situations. Whenever you are combining two or more images (in Photoshop terms, compositing ), the elements you paste or drag in from another document over the background image are added on separate layers. You can use the Layers palette to control precisely how these elements are combined. You can control the opacity of objects you paste onto a layer or paint that you apply to it. (The layer itself is transparent, even if you set the paint on it to 100% opacity.) You can also control the blending modes that affect how one layer appears on top of another, just as you can when painting over an image or background. OpacityThe Opacity slider at the top of the Layers palette controls the opacity of the active layer. You used it briefly earlier to change the opacity of the bacon. Make the slider appear by clicking the triangle to the right of the percentage window. It can be adjusted from 0%100% by dragging the slider. If you'd rather not access the slider, enter a value by typing for 100%, 1 for 10%, 2 for 20%, and so on. If you desire more precise control, simply type the digits of the measurement you desire ( 57 , for instance) in quick succession. This trick works with any tool that doesn't have its own Opacity settingwith tools that do have Opacity settings, use the keyboard to adjust the setting for the tool rather than the layer. Let's practice some more with the Opacity slider. You should still have the sandwich open on your screen. Make the tomato layer active and drag the Opacity slider (by clicking and holding down on the arrow button to make it appear) to about 75%. Can you still see the tomato? Yes, but it's sliced very thin. Drag the slider down to 10% and then to 0%. Then move it back to 100% again. Pretty cool, huh? The Opacity slider has no effect on the Background layer. It always remains at 100% opacity. There is, however, a way around this. There is a difference between the background of your image and what Photoshop sees as the background to your layers. You can create a document with a transparent background by choosing File Figure 11.12. Making a transparent background. If you don't see the checkerboard pattern, open Edit
Now that you have a document with a transparent background, let's create another layer for the sandwich. I happen to like pumpernickel bread, so I'll make a slice of that, using a brush and some brown paint, and applying the Grain filter and the Blur filter to complete the look. Then I'll make a second layer, with a toothpick to hold the sandwich together, like they do in the delicatessen. I can make the toothpick translucent plastic by reducing the opacity. As a final touch, I'll add a third layer with an olive. In Figure 11.13, you can see the top of the sandwich, set in place. Figure 11.13. Each layer can have a different transparency. If you look closely, you can see the sandwich through the toothpick, but not through the olive. Layer Blending ModesIn Hour 8, "Digital Painting," you learned about blending modes and how they affect the way paint is applied. Almost the same set of modes is available to you for blending layers, and they produce the same general effects, but only on the layers beneath the one to which you have applied the blending mode. (If you're not clear on what the effects are, refer back to Hour 8.) The layer in this case is the blend color, and the image below is the base color . As with the painting tools, the layer blending modes are found on a pop-up menu on the Layers palette. Just as a reminder, the blending modes are
You can apply blending modes directly from the Layers palette or by using Layer Linking LayersIf you select more than one layer in the Layers palette (Command+click or Control+click), you can click the Link Layers button at the bottom of the palette. Each linked layer will have a piece of linked chain next to its name. This indicates that the layer is linked to the active layer, meaning that if you move the contents of the active layer, the linked layers move with it. Figure 11.14 shows the Layers palette with sandwich layers linked to the bread. Figure 11.14. Layers linked to the active layer move with it. In this case, the fillings move if you slide the bread off the plate. Layer Groups Layer groups help you organize and manage collections of layers. After you define a group of layers, you can collapse them or reveal them as necessary, without actually flattening the image. With the sandwich example, you could have designated everything between the slices of bread as a group. If you needed to move the individual elements or change their size or color, you'd do so to the whole set rather than a layer at a time. Layer groups must be contiguous. You can't make a set of layers 1, 3, and 5 unless you move layers 2 and 4 to above or below the layer group. To create a layer set, select the layers you want to group , then use the command Layer Merging LayersThe more layers you add to an image, and the more effects that you add to those layers, the larger your image file will become. If you have a large capacity hard drive and can back up to removable media, size isn't a problem. It does, however, make a big difference if you want to use your files for anything else, such as publishing in print or on the Web. The only formats in which you can save a multilayered image are TIFF and the Photoshop native format, which is great for Photoshop, but bad for other uses. For the Web, you need to save images as GIF, PNG, or JPEG. For print, you probably will need to save as TIFF, although layered TIFF files can be very large. That's why you need to either merge layers or flatten the image when you're done working with it. The differences between merging and flattening are as follows :
You can use either the Layer menu or the Layers palette menu to merge or flatten layers, or the keyboard combination Command+E (Mac) or Control+E (Windows) to Merge Down. Figure 11.15 shows the Layer menu with the Flatten Image command highlighted. Figure 11.15. This compacts all the layers to one. Using Layer Comps"What the heck is a layer comp?" you're probably asking. Comps, or composites, are familiar to advertising artists . They are the mock-ups made so the client can see how a print ad will look, and include rough illustrations, sample type, the product logo, and so on. Often, several comps are made of the same ad, with elements in different colors or different positions , to see which looks best. One of the most useful features introduced in recent versions of Photoshop is the capability to create and save layer comps. Layer comps in Photoshop and ImageReady save multiple configurations of a file by recording the visibility, layer style, and positions of selected layers. Instead of needing to create a half dozen examples of something like a logo as six separate documents, you can create one, and then add as many comps as you need. To save a layer comp, first open the Layer Comps palette. When the image is where you want it, with the right layers showing and the others hidden, click the New Layer Comp button at the bottom of the palette. (It looks just like the New Layer button on the Layers palette.) You can name the layer comp, and select the attributes to preserve in the resulting dialog box, shown in Figure 11.16. You can also add notes about the image by typing them into the Comment field. Figure 11.16. Naming layer comps helps you keep track of which is which. In Figure 11.17, I've created a bunch of possible logos for a local veterinarian. They are all listed on the Layer Comps palette, and if you look at the Layers palette as well, you can see that they are simply different combinations of visible layers. Figure 11.17. To switch to a different comp, click it on the Layer Comps palette. Transferring Layered Images to ImageReadyIf you're working on an image for use on a web page, you'll probably want to do the initial work in Photoshop and then jump into ImageReady to save it for Web use. You can transfer layered images between Photoshop and ImageReady by simply clicking the Edit in ImageReady button at the bottom of the toolbox. All layers, layer masks, layer effects, and adjustment layers are preserved. (Adjustment layers can be applied and edited only in Photoshop, but can be viewed in ImageReady.) Layer StylesPhotoshop and ImageReady both include layer styles , a number of automated effects that you can apply to layers, including drop shadows, glows , beveling, and embossing, as well as a color fill effect. You've already tried the Inner Bevel style on the mayonnaise. ImageReady also includes pattern and gradient layer effects. Fig-ure 11.18 shows the Photoshop Layer Style submenu. Figure 11.18. Most of these styles are best used with type or with a selected object. We'll apply these effects to type and to composited images in Hours 16, 18, and 20. |
New. For the contents, choose Transparent, as shown in Figure 11.12. When the canvas opens, youll see a checkerboard pattern as a placeholder, indicating that there's nothing on the layer. If you look at the Layers palette, you'll notice that the blank page is called Layer 1 and not Background. That's to help you remember that you can change the opacity. Anything you paint on that layer will have a transparent background. Anything you copy from another source and paste in will go on a new layer that can also be made transparent. 
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