Photoshop.CS.Bible [Electronic resources] نسخه متنی

Chapter 8) and channels to selections (Chapter 9):

Ctrl-click (Win) or z -click (Mac) an item in the Layers palette to convert the transparency mask for that layer to a selection outline.

To add the transparency mask to an existing selection outline, Ctrl+Shift-click (Win) or z -Shift-click (Mac) the layer name. The little selection cursor includes a plus sign to show you that you're about to add.

To subtract the transparency mask, Ctrl+Alt-click (Win) or z -Option-click (Mac) the layer name.

And to find the intersection of the transparency mask and the current selection outline, Ctrl+Shift+Alt-click (Win) or z -Shift-Option-click (Mac) the layer name.

If you're uncertain that you'll remember all these keyboard shortcuts, you can use Select Load Selection instead. After choosing the command, select the Trans-parency item from the Channel pop-up menu. (You can even load a transparency mask from another open image if the image is exactly the same size as the one you're working on.) Then use the Operation radio buttons to merge the mask with an existing selection.

Selection outlines exist independently of layers, so you can use the transparency mask from one layer to select part of another layer. For example, to select the part of the background layer that exactly matches the contents of another layer, press Shift+Alt+[ (Shift-Option-[ on the Mac) to descend to the background layer and then Ctrl-click (Win) or z -click (Mac) the name of the layer you want to match.

The most common reason to borrow a selection from one layer and apply it to another is to create manual shadow and lighting effects. After Ctrl-clicking (z -clicking on the Mac) on a layer, you can use this selection to create a drop shadow that precisely matches the contours of the layer itself. No messing with the brush or the lasso tool — Photoshop does the tough work for you.

Now, you might think with Photoshop's extensive range of layer styles, manual drop shadows, and the like would be a thing of the past. After all, you have only to choose Layer Layer Style Drop Shadow and, bang, the program adds a drop shadow. But the old, manual methods still have their advantages. You don't have to visit a complicated dialog box to edit a manual drop shadow. You can reposition a manual shadow from the keyboard, and you can expand and contract a manual shadow with more precision than you can an automatic one.

On the other hand, the old ways aren't necessarily always better. A shadow created with the Drop Shadow command takes up less room in memory, it moves and rotates with a layer, and you can edit the softness of the shadow long after creating it.

What we have is two equally powerful solutions, each with its own characteristic pros and cons. Therefore, the wise electronic artist develops a working knowledge of both. This way, you're ready and able to apply the technique that makes the most sense for the job at hand.

Drop shadows

In these first steps, I take the lovable, cuddly mutt shown in Figure 12-16 and make him cast a drop shadow on the sign beside him. Hopefully no one will be bitten as I demonstrate how the effect works.

Figure 12-16: A doggie in dire need of a drop shadow, if not Prozac.

STEPS: Creating a Drop Shadow

Select the subject that you want casting the shadow. In my case, I selected the pooch by painting a mask in a separate mask channel. These days, I add a mask to nearly every image I create to distinguish the foreground image from its background. I converted the mask to a selection outline by Ctrl-clicking (z -clicking on the Mac) the mask name in the Channels palette and then pressing Ctrl+tilde (z -tilde on the Mac) to switch back to the composite view.

Send the image to a separate layer by pressing Ctrl+J (z -J on the Mac). Now that the selection is elevated, you can slip in the drop shadow beneath it.

Retrieve the selection outline for your new layer and apply it to the background layer. To do this, Ctrl-click (Win) or z -click (Mac) the new layer name (presumably Layer 1) and then press Shift+Alt+[ (Shift-Option-[ on the Mac) to switch to the background layer. Because I saved the mask to a separate channel, I could have instead Ctrl-clicked (Win) or z -clicked (Mac) on the Mask item in the Channels palette to retrieve the selection. Or I could have pressed Ctrl+Alt+4 (z -Option-4 on the Mac).

To create a softened drop shadow — indicative of a diffused light source — choose Select Feather or press Ctrl+Alt+D (z -Option-D on the Mac). The Radius value you enter depends on the resolution of your image. As a general rule, dividing the resolution of your image by 20 can yield pretty good results. (Note that this isn't a hard and fast rule; by all means, forget about the math if necessary and do what looks right.) My image is 300 ppi, so I entered 15. Then press Enter or Return to soften the selection.

Press Ctrl+J (z -J on the Mac) to send the feathered selection to a new layer.

Fill the feathered area with black. If necessary, press D to make the foreground color black. Then press Shift+Alt+Backspace (Shift-Option-Delete on the Mac) to fill only the area inside the transparency mask. A slight halo of dark pixels forms around the edges of the image.

Press Ctrl (Win) or z (Mac) with the arrow keys to nudge the shadow to the desired location. I nudged the shadow 25 pixels to the left. (Press Ctrl+Shift+ arrow key or z -Shift-arrow key to nudge the shadow in 10-pixel increments.)

Lower the Opacity setting. If the shadow is too dark — black lacks a little subtlety — change the Opacity value in the Layers palette to change the opacity of the shadow. Or press M to make sure a selection tool is active and then press a number key to change the opacity. I typically press 7 (for 70 percent), but I'm probably in a rut. Figure 12-17 shows the results so far.

Figure 12-17: A manually created drop shadow behind this canine cutie gives a feeling of depth, yet ironically still a feeling of flatness.

Press Ctrl+T (z -T on the Mac) to apply Free Transform, and distort the shadow. Ctrl-drag (z -drag on the Mac) on the corner handles to create a perspective distortion, as seen in Figure 12-18. This is an advantage of creating a drop shadow manually; it can easily be resized, filtered, and transformed to suit your whim.

Figure 12-18: The Free Transform command lets me distort my drop shadow to give a sense of perspective and true depth to the image.

Press Ctrl+Shift+X (z -Shift-X on the Mac) to tweak with the Liquify filter. The shadow didn't line up perfectly with the dog's legs, so I applied the Liquify filter and nudged the shadow around until things looked perfect, as shown in Figure 12-19.

Figure 12-19: A drop shadowed dog who truly belongs in this image, and knows it.

Halos

Creating a halo is similar to creating a drop shadow. The only differences are that you must expand the selection outline and fill the halo with white (or some other light color) instead of black. Again, doing this manually gives you a good deal of room for creative expression. The following steps tell all.

STEPS: Creating a Less-than-Heavenly Halo

Follow Steps 1 through 3 of the preceding instructions. You end up with a version of the selected image on an independent layer and a matching selection outline applied to the background image. (See, I told you this was like creating a drop shadow.)

Expand the selection outline. Unlike a drop shadow, which is offset slightly from an image, a halo fringes the perimeter of an image pretty evenly. You need to expand the selection outline beyond the edges of the image so you can see the halo clearly. To do this, choose Select Modify Expand. An Expand By option box greets you; I entered 30. (The maximum permissible value is 100; if you want to expand more than 100 pixels, you must apply the command twice.)

Choose Select Feather and enter the same value you entered in the Expand By option box. Again, I entered 30.

Send the selection to a new layer. Press Ctrl+J (Win) or z -J (Mac).

Fill the halo with white. Assuming the background color is white, press Ctrl+Shift+Backspace (z -Shift-Delete on the Mac). Figure 12-20 shows the result.

Figure 12-20: I selected, expanded, feathered, and filled our doggie buddy to make a halo.

From there, I applied the ZigZag filter, as shown in Figure 12-21. This created a nice spiraling effect to the glow. I then created another layer, used the brush tool and a Wacom tablet to paint in some lightning bolts shooting out from the glow, and finally dropped some fire from another image into the waiting mouth of Fido. Figure 12-22 shows demon dog in his full glory.

Figure 12-21: The ZigZag filter applies a swirling motion to the pooch's halo.

Figure 12-22: Halos don't always have to be used for an angelic effect.