Those are only two of many ways to create a new layer in Photoshop. Here are a few others:

Figure 13.2. Ctrl-drag (

-drag on the Mac) a selected portion of an image, and drop it into a different image window to introduce the selection as a new layer. As you can see in the Layers palette, the moon is being moved into place as a new layer in front of the original background image.

Incidentally, you also can create a new layer by choosing New Layer from the Layers palette menu or the Layer menu's New submenu (choose Layer

Figure 13.3. Nearly all the commands in the Layers palette menu are duplicated in the Layer menu — and supported by buttons at the bottom of the Layers palette itself.

If you want to specify a more meaningful name, add the Alt (Win) or Option (Mac) key. Press Ctrl+Alt+J (

When creating a new layer from the keyboard, press Ctrl+Shift+Alt+N (

Figure 13.4. Press Alt (Option on the Mac) to force the display of the New Layer dialog box, which lets you name the new layer.

To clone the active layer, you can choose Layer

To specify a name for the cloned layer or to copy the layer into another image, Alt-drag (Option-drag on the Mac) the layer onto the new layer icon. Always the thoughtful program, Photoshop displays the dialog box shown in Figure 13.5. You can name the cloned layer by typing something in the As option box. To apply the layer to some other open image, choose the image name from the Document pop-up menu. Or choose New, and type the name for an entirely different image in the Name option box, as the figure shows.

Figure 13.5. You can duplicate the layer into an entirely different image by Alt-dragging (Option-dragging on the Mac) the layer onto the new layer icon in the Layers palette. This dialog box helps you complete the process.

Tip

You can clone a layer by simply Ctrl+Alt-dragging (

You can select a different layer by clicking its name in the Layers palette. The layer you click becomes active, enabling you to edit it. Here are some other layers palette tricks:

You also can ascend and descend the layer stack from the keyboard:

If you right-click (Control-click on the Mac) any layer in the Layers palette, a pop-up menu (shown in Figure 13.7) appears. Among the pop-up menu's commands is an option called "Select Similar Layers." Similar? What does that mean? It means layers that have similar content in terms of size, shape, color, modes, and styles, so referring again to Figure 13-7, if the command were to be chosen in the image shown (with the "Moon copy 2" layer active), the Moon and Moon copy layers would also be selected automatically.

The Select Similar Layers command can be a great way to select several duplicate layers at once without having to hunt through (and possibly scroll through, if you have lots of layers) a long list of layers in the palette to find the ones you want to select for moving, resizing, linking, or dragging to another image in the workspace.

Figure 13.7. Choose Select Similar Layers to grab all the layers that have much in common.

Although the selection outline disappears when you convert a selection to a layer, no information is lost. Photoshop retains every nuance of the original selection outline — whether it's a jagged border, a little bit of anti-aliasing, or a feathered edge. Anything that wasn't selected is now transparent. The data that defines the opacity and transparency of a layer is called the transparency mask.

To see this transparency in action, click the eyeball icon in front of the background item in the Layers palette. This hides the background layer and enables you to view the new layer by itself. In Figure 13.8, the background (the desert) is hidden (note the missing eyeball icon next to that layer) and only the moon layer is visible — and all of that layer except for the moon is transparent and filled with a checkerboard pattern. Opaque areas look like the standard image, and translucent areas, where they exist, appear as a mix of image and checkerboard — the visibility of the checkerboard, of course, dictated by the opacity of the content.

Figure 13.8. When you hide the background layer, you see a checkerboard pattern that represents the transparent portions of the layer.

Tip

If the checkerboard pattern is hard to distinguish from the image, you can change the appearance of the pattern. Press Ctrl+K and then Ctrl+6 (

If you apply an effect to the layer while no portion of the layer is selected, Photoshop changes the opaque and translucent portions of the image but leaves the transparent region intact. For example, if you press Ctrl+I (

Only a few operations affect the transparent areas of a layer, and most of these are limited to tools. You can paint on transparent pixels to make them opaque. You can clone with the Clone Stamp or smear pixels with the edit tools. To send pixels back to transparency, paint with the Eraser. All these operations change both the contents of the layer and the composition of the transparency mask.

Tip

You also can fill all pixels by pressing Alt+Backspace (Option+Delete on the Mac) for the foreground color and Ctrl+Backspace (

When a portion of the layer is selected, pressing plain old Backspace (Win) or Delete (Mac) eliminates the selected pixels and makes them transparent, revealing the layers below. Note that this is not some display trick; you're actually clearing the pixels within the selection, so to get them back, you'll have to use Undo or use the History palette to go back in time to the pre-Clear state.

At the bottom of the layer stack is the Background layer, the fully opaque layer that represents the base image. The background image is as low as you go. Nothing can be slipped under the background layer, and pixels in the background layer cannot be made transparent, unless you first convert the background to a floating layer. Blend modes and styles cannot be applied to the layer, nor can the background be changed in terms of its Opacity or Fill; these options become dimmed while the background layer is active.

To convert your Background layer to a floating layer, double-click the layer labeled Background in the Layers palette. A dialog box appears. Type a name for the new layer — Photoshop suggests Layer 0 — and press Enter or Return. You can now change the order of the layer or erase down to transparency.

In Figure 13.9, the background image has been converted to a layer. Had this particular image included a path that encircled the background layer's subject, or had the background content not completely filled the Background layer, you could Ctrl-click (

Figure 13.9. After converting the Background layer to a floating layer, the white space around the content (canvas area) was selected and deleted, leaving transparency in its wake.

Tip

To convert the active layer to a background layer when there is currently no background layer, choose Layer

To establish a blank background, create an empty layer by pressing Ctrl+Shift+N (

Figure 13.10. A new background layer is added below the main image layer (the former background) and a wood texture is added. Stroke and Drop Shadow layer styles were then added to the desert layer to give the composition a little false depth.

Photoshop permits only one background layer per image. If an image already contains a background layer, the command Layer

Layers would be rather limited in terms of enabling you to rearrange your image content if you couldn't change their stacking order. Luckily, Photoshop makes it easy to move layers up and down in the stack, making things overlap when they didn't before, preventing overlaps where you don't want them, and placing content behind other content so you can either see it (by reducing the opacity of the uppermost layer) or so you can't see some or all of the underlying layer. Rearranging the order of your layers also can have interesting effects on any blending modes previously applied to your layers.

You can reorder layers in two ways. First, you can click and drag a layer name up or down in the scrolling list to move it forward or backward in layering order (your mouse pointer turns from a pointing hand to a little determined fist while you're dragging). The only trick is to make sure that the black bar appears at the point where you want to move the layer before you release the mouse button, as illustrated in Figure 13.11.

The second way to reorder layers is to choose a command from the Layer

You can move faster if you remember the following keyboard shortcuts:

Figure 13.11. Here, one of the three layers containing versions of the moon is in transit, headed for the top of the stack. When restacking layers, consider not just their actual content, but any effects, such as blend modes or opacity, applied.

When layer content is really tiny or is right next to, slightly behind, or mostly obscured by other content, it can be hard to spot and even harder to click it with your mouse to move it. To make your layers easier to see and click on, no matter how small, see-through, or camouflaged they may be, choose View

To use the Layer Edges command feature, click the layer you want to see highlighted by an edge (use the Layers palette to click it). Then issue the View

After you turn this option on, whichever layer you activate — be it by selecting the layer by clicking it in the Layers palette or by clicking the layer content directly with your mouse — is encompassed by the dark blue box. If you press Shift or Ctrl (

Figure 13.12. Turn on Layer Edges to display a helpful box that surrounds the active layer.

To stop seeing the boxes, you can either reselect the command to toggle it off or turn off the view of all Extras (guides, slice borders, and so on) with the View

When you convert an anti-aliased selection to a layer, you sometimes take with you a few pixels from the selection's previous background. These fringe pixels can result in an unrealistic outline around your layer that really makes the selection-based layer stand out in its new location. Figure 13.13 shows this very problem in magnified detail from an early attempt to add the skeleton to the desert image. Although the selection outline is accurate — it was done at a high zoom, with great care — a few dark pixels from around the skeleton (he used to be on a busy background) came along with him.

Figure 13.13. This enlarged detail of a newly inserted skeleton layer demonstrates the extra, unwanted pixels that can accompany gross selections like those made with the Lassos or the Magic Wand.

You can instruct Photoshop to replace the fringe pixels with colors from neighboring pixels by choosing Layer

It's not that Defringe never works; sometimes the results are satisfactory. But keep in mind that it's not available when a selection is active or when the layer has a layer mask or vector mask.

Figure 13.14. Here the Defringe command was set to a Width value of 1 to replace the pixels around the edges of the skeleton layer with colors borrowed from neighboring pixels.

Photoshop provides two additional commands under the Layer

Adobe says that these commands were designed for compositing a scene rendered in a 3D drawing program against a black or white background. But for other purposes, they almost never work — unless your content did in fact come from a stark white or black background.

Tip

If you encounter unrealistic edge pixels and the automatic matting commands don't solve your problem, you may be able to achieve better results by fixing the edges manually. First, switch to the layer that's making you crazy and Ctrl-click (Win) or

Photoshop lets you blend layers like no other program available. In fact, Photoshop does such a great job that it takes almost all of Chapter 14 to explain these options in detail. This section serves as an introduction so that you're at least aware of the basics. If you have bigger questions, Chapter 14 is waiting to tell you the whole story.

The Layers palette provides four basic ways to blend pixels between layers, as shown in Figure 13.15. None of these techniques permanently changes as much as a pixel in any layer, so you can always return and reblend the layers at a later date.

Although layers are wonderful and extremely helpful devices, they have their drawbacks. Of course, none of these negative aspects outweigh their usefulness. Layers do expand the size of an image in RAM and ultimately lead to slower performance, and as noted in Chapter 3, only four formats — PDF, TIFF, the new PSB, and native PSD — permit you to save layered compositions. You can use layers in the construction of any image. It's just that when you go to save it in any format other than those four, your layers are combined into a single layer, and further editing on an individual layer basis is impossible. Of course, you can save a PSD or TIFF version of the artwork, too, and that way you'll retain an editable, layer-laden copy.

With the size and performance-eating problem in mind, you may want to put your image on a diet of sorts. To slim down your image, Photoshop provides the following methods for merging layers:

You also can throw a layer away. Drag the layer name onto the trash can icon at the bottom of the Layers palette, click the trash can icon to delete the active layer, or right-click (Control-click on the Mac) the layer to be deleted and choose Delete Layer from the pop-up menu. So many choices.

Tip

Here's a good one for you: If the active layer is linked to one or more other layers (see the upcoming section "Linking and unlinking"), you can delete all linked layers in one fell swoop by Ctrl-clicking (Win) or

As already mentioned, only four file formats — PDF, TIFF, PSB, and the native Photoshop format — save images with layers. If you want to save a flattened version of your image — that is, with all layers fused into a single image — in some other file format, choose File

The Save As command does not affect the image in memory. All layers remain intact. So if you select the As a Copy option with the Layers option deselected — which is a good idea, really — Photoshop doesn't even change the name of the image in the title bar. It merely creates a flattened version of the image on disk. Nevertheless, be sure to save a layered version of the composition as well, just in case you want to edit it in the future.

With the release of Photoshop CS3, there were a few changes to the way you link and unlink layers. Of course, there's no big change in your overall capabilities in terms of layer linking and unlinking, but the procedure for linking layers (and then unlinking them later) has changed a bit for those of you whose most recent Photoshop experience was CS or version 7.

First, there is no longer any link check box or chain icon next to each layer. In Photoshop CS and its layer-supporting predecessors, in addition to the box where the eyeballs live, there was another column of boxes, which when clicked, would display a chain icon. This meant that the selected layers (you had to select them before clicking in the box) were linked. You could then unlink layers by clicking the chain icon and breaking the link.

Now, the Link Layers button is on the bottom of the palette, and you use it to link and unlink selected layers. Figure 13.17 shows two linked layers, and the Link Layers button is labeled.

Figure 13.17. Select the layers you want to link, and then click the Link Layers button, found at the lower-left end of the Layers palette buttons.

You also can link layers with the shortcut menu. As you may recall from the section "Switching between layers" earlier in this chapter, you can bring up a pop-up menu listing the layers in an image by Ctrl-right-clicking (

When you drag-and-drop linked layers from one image window into another, all linked layers move together and the layers retain their original order. If you want to move just one layer without its linked buddies, drag the layer name from the Layers palette and drop it into another open image window.

When you have just two layers linked, unlinking is just as easy as previously stated: With the layers selected, click the Link Layers button and the link is broken. The chain icon leaves the layers, and the link is no more. But what if you have more than two layers linked? Is it an all-or-nothing proposition? Nope. If you have three, four, or more layers linked, to unlink them all, right-click (Control-click on the Mac) any one of the linked layers and choose Select Linked Layers from the pop-up menu. To unlink just one or two (or any number, just not all) of the linked layers, select just those that you want to unlink and click the Link Layers button. The layers you didn't select remain linked, but the selected layers are no longer part of the chain gang.

In versions of Photoshop prior to CS2, layers could be placed in sets: Using the Folder button at the foot of the Layers palette, you could create a set and click and drag layers into it, and you also could create nested sets by creating sets within sets and dragging layers into the nested sets. It all worked like file management in Windows (or even on the Mac), where you have folders and subfolders, and files can be stored in them to keep your work organized. Sets served the same purpose in Photoshop, enabling you to organize your layers and deal with them in large, well, groups. That may be why the name was changed, huh?

Anyway, now sets are called groups, and you call the process of creating them and placing layers in and taking layers out of them grouping and ungrouping layers. For those of you who are new to grouping layers, or if you're familiar with putting layers in the aforementioned sets, here's how the whole grouping/ungrouping thing works:

First, click the Create a New Group button (it's still a folder icon button) at the foot of the Layers palette. A generically named Group layer appears in the palette, called Group 1 (if it's your first in the current image). You also can Alt-click (Option-click on the Mac) the Create a New Group button and open the New Group dialog box shown in Figure 13.18. Through this dialog box, you can name your new group, choose a color for its display in the Layers palette, and choose a Mode and Opacity for it. You'll note that the default Mode is Pass Through, and that will be explained shortly.

Figure 13.18. Choose the Create a New Group command or Alt-click (Option-click on the Mac) the folder icon at the bottom of the Layers palette to create and name a new group.

The group appears as a folder icon in the Layers palette scrolling list. There's also a little triangle next to the folder icon, which you'll use to display and collapse (not hide, as in not showing in the image) the list of grouped layers. The group's visibility as a whole is indicated by the eyeball icon to the left of the group's name.

To add a layer to the group, click and drag the layer name within the Layers palette and drop it on the folder icon. That little fist mouse pointer you saw in the coverage of restacking layers returns and follows you as you drag the layer up or down to the group in which it belongs. Figure 13.19 shows a new group in place (Lens Flare examples), with layers already in it, and an existing group (Callouts) with its layers collapsed.

Photoshop also lets you place groups inside of other groups, a process called nesting. Photoshop allows you to nest groups up to five levels deep. Nesting layer groups can be a great way to better organize your layers. To place one group inside another, simply drag-and-drop it onto the other group in the same manner you would a layer. As it does when you place a layer into a group, Photoshop applies the blend mode of the master group to every layer and nested group within it when the mode is not set to Pass Through.

Figure 13.19. A new group and its members — and a member being brought to its first meeting

Here are some other ways to create and modify groups:

Anytime a group name is active in the Layers palette, you can move or transform all layers in the group as a unit, much as if they were linked. To move or transform a single layer in the group, just select that layer and go about your business as you normally would.

New in Photoshop CS3, the Auto-Align Layers command aligns selected layers in a single image, based on any similar content — common edges or corners or actual overlapping content, such as would occur if you took a series of images to create a panorama, or if you took two pictures of the same scene, but with a different person or other object in the foreground in each image.

Through the command's dialog box, shown in Figure 13-20, you can choose how the alignment takes place, choosing from different special perspective and positioning effects. Before you begin the Auto-Align process, however, you can lock one of your layers (one of the layers to be aligned) and make it a reference point for the other layers you want Photoshop to align for you. By locking the layer, you establish a position against which the other layers will be aligned, based on your subsequent selection in the Auto-Align Layers dialog box. If you choose not to lock a layer and make it a reference, Photoshop makes its own decisions and selects one of your layers as the reference for the alignment of the other selected layers.

To use the Auto-Align Layers feature, start by placing the layers you want to align in the same image. This can be done by copying content from other images into the target image or creating layers from content within the image you want to align. Once you have the layers in place, select them within the Layers palette, and then choose Edit

Figure 13.20. The Auto-Align Layers dialog box lets you choose how your selected layers will line up.

To turn content into a Smart Object, simply select the layer or layers from within any Photoshop image; it can be a PSD or TIFF file, or saved in any other format that supports the use of layers. With the layer(s) selected, right-click the layer names in the Layers palette (Control-click with a single button mouse on the Mac) and choose Convert to Smart Object. You also can choose Layer

Figure 13.21. Select three layers (left), and turn them into a Smart Object (right). The Smart Object layer keeps the name of the uppermost layer you selected, which is why you can see us changing that name to something more appropriate here.

Tip

You can use the Layers palette to create your Smart Objects, too. Select the layer(s) to be made into an object, and right-click (Control-click on the Mac) to display a pop-up menu. Choose Convert to Smart Object from the menu, and the object is created. The Layers

So you've made a Smart Object. Now what do you do with it? You can double-click the object layer in the Layers palette or choose Layers

Figure 13.22. Take this good advice to make sure your edited Smart Object can return to the image from whence it came.

After clicking OK to acknowledge this great advice, you're presented with a new image window, titled with the same name as the original uppermost layer in the Smart Object. The format for the new image is PSB (large document format), and the image consists of the layer(s) you grouped into the Smart Object. Figure 13.23 shows the resulting main .psb file and its Layers palette.

You can edit the new PSB file as you would any Photoshop file using virtually any of the tools, commands, filters, and so forth that you want. You can use the Transform tools to rotate, skew, scale, and even warp the content, too (but you'll find Distort and Perspective dimmed). Warping, which also can be applied to transform the PSB file content, is discussed later in this chapter.

Figure 13.23. One Smart Object becomes a new image with three (in this case) layers.

After you've finished your edits, you can use the File

To export a Smart Object, select Export Contents from the pop-up menu that appears when you right-click (Control-click) the object. A Save dialog box opens through which you can give your file a name (PSB is the default format, but you can pick another) and choose a location for the file. After you've saved the file, it can be opened in Illustrator as well as many other vector-based editing programs. You also can open it in Photoshop. After the edits are performed, you can save the image and reopen the original image in Photoshop — "original image" refers to the one from which the original layers that became the object came. The changes you made in the other program are reflected, and the content is rerasterized.

If you choose Replace Contents from the Layer

Speaking of stacking, another command you may have noticed in the Layer

Understanding Stack Mode

So what is a stack, and what is Stack Mode? An image stack is a combination of images, represented by layers in an image file. It's created from multiple images and builds a single new image from the images in the stack. This is different from a simple composite image, where you manually drag content from multiple images into a target image, and it's different from blending (as discussed in Chapter 14), because the image your stack builds can be very different from the image/s used to build it. It might be in a different mode (set through the Image

Making an image stack

To create an image stack, you take two or more images, convert them to layers in a single image file, and then convert those layers to a Smart Object (using techniques discussed previously in this chapter). You select all the layers and choose Layer

Applying Stack Mode options

After the images have been combined into a new image as layers and those layers converted to a Smart Object, you can apply any one of 11 different Stack Modes to the image stack, or you can apply no specific mode and allow the combining of the image-based layers into a Smart Object stand on its own in terms of the impact the combined layers have on each other and their resulting single layer.

Figure 13.25 shows our sample figure of three spheres — red, green, and blue (yes, we KNOW it's grayscale, but check the color section!). Figure 13.26 shows the results of the 11 Stack Modes when applied to the image.

Figure 13.24. The Stack Mode submenu

If you choose to apply a Stack Mode, here are your options: Be forewarned that if you found the Custom filter's math daunting (see Chapter 12), these would blow your mind if we got into all the calculations that go into the application and execution of these modes. Here's the list, though, and you can experiment with each one, using your own images or those you'll find on this book's CD.

Figure 13.25. The "before" shot

The first options have some common elements: If there is only one layer in the stack, the size of the original image stack is maintained, and output depth is consistently 32 bits/channel. As a result, some image modes change, such as CMYK, LAB, and Multichannel — images in these modes become RGB images and maintain the same channel order.

• Entropy: When this one is applied, the result is the binary entropy of the non-transparent pixel values, calculated per channel. There is a probability of value equal to the result of the number of occurrences of the value divided by the total number of non-transparent pixels.

• Kurtosis: Here, the result is the statistical kurtosis of the non-transparent pixel values, on a per-channel basis. Kurtosis is a measure of peakedness or flatness compared to a normal distribution. The kurtosis for a standard normal distribution is 3.0, and a Kurtosis of more than 3 is present in a peaked distribution, and kurtosis less than 3 means you have a flat distribution.

• Maximum: This one gives you the maximum of the non-transparent pixel values, on a per-channel basis. Figure 13.24 shows the results of this Stack Mode, with the original (unstacked) Smart Object shown on the left.

• Mean: Where the input stack is 8 or 16 bits/channel, the resulting image is 16 bits/channel. If the input stack is 32 bits/channel, the resulting image is, too. This Stack Mode results in an average of the non-transparent pixel values, calculated on a per-channel basis.

• Median: The median Stack Mode results in the median value of the non-transparent pixels, calculated per channel.

• Minimum: Here, the result is the minimum of the non-transparent pixel values, per channel. Figure 13.26 shows the impact of this Stack Mode on a Smart Object. The original object appears on the left for comparison.

  

  Figure 13.26. Here you see the results of applying Stack Modes to our original image.

• Range: This gives you the maximum, minus the minimum, of the non-transparent pixel values, per channel.

• Skewness: In this case, the result is the statistical skewness of the non-transparent pixel values, again, on a per-channel basis. The skewness is a measure of symmetry or asymmetry around the statistical mean, relative to the non-transparent pixels. Positive skewness values are found when the distribution is skewed to the high side of the mean, and negative skewness values are found when the distribution is skewed to the low side of the mean.

• Standard Deviation: This Stack Mode gives you the statistical variance of the non-transparent pixel values, on a per-channel basis. The standard deviation is equal to the Square Root multiplied by the variance.

• Summation: Here, the stack displays the sum of the non-transparent pixel values, calculated on a per-channel basis.

• Variance: In this case, the result is the statistical variance of the non-transparent pixel values, again calculated per-channel.

These options have some things in common, too. First, these Stack Modes preserve the pixel depth, image size and image mode of the original images in the stack, and when there is only one layer in the stack (if you selected all the layers before creating the Smart Object, resulting in a single layer), the result is a duplicate of the input.

Tip

If all the Stack Mode descriptions you just read have left your brain spinning or you gave up after the first few, don't despair. One of the ways you can use Stack Modes, without having to understand the math behind them, is to reduce noise in an image. Tinker with the modes — each one has a different impact on each different image you work with — to find the one that eliminates the pixels that are creating unpleasant blips of color, light, or darkness in your image.

As you may have discovered when trying to manipulate the style or fill of type, shape layers, vector masks, or Smart Objects, you can't use the Paint Brush or any Filter on layers that contain vector data. A prompt, such as the one shown in Figure 13.27, appears. What to do? Read on.

Figure 13.27. Stop right there. You can't apply many tools to vector-based image content, like type.

First, let's remind ourselves — what is vector data? Think (or refer directly) back to Chapter 1, where we talked about the difference between raster images and vector images. Vector images contain mathematical information, all of which combines to display content that's a certain size, filled with a certain color, bearing an outline of a certain width, and so on. Raster image are pixel-based, and the individual pixels can therefore be painted, filtered, and otherwise manipulated in ways that are impossible when the tool runs smack into a bunch of numbers and values.

To rasterize a layer, any layer, simple right-click (Control-click on the Mac) the layer, and choose Rasterize Layer from the pop-up menu. You also can select the layer in the Layers palette, choose Layer

Figure 13.28. Rasterize any type of layer, turning it from vector data to pixels that Photoshop can easily work with.

Just like a Smart Object can protect selected layers from loss of quality when transferred to and from an external editing program, the Layers palette can protect a layer from any kind of changes by allowing you to lock it. Photoshop also lets you lock only some attributes of a layer and leave other attributes unlocked, thus making this protection very flexible. Figure 13.29 labels the four Lock buttons available in the Layers palette. Here's how they work:

Photoshop shows you which layers are locked by displaying two kinds of lock icons in the Layers palette. As labeled in Figure 13.29, the hollow lock (white, as shown) means one attribute is locked; the filled lock (black) means all attributes are locked.

Photoshop's grids and guides allow you to move selections and layers into alignment. They're not the only tools that enable you to do this, of course, because you always have the Align and Distribute commands in the Layers menu, but when combined with the Move tool, guides and grids make it much easier to create rows and columns of image elements and even align layers by their centers. This capability, along with the enhanced alignment indicators known as Smart Guides (you'll read about them shortly), enables you to achieve a much greater control over your image elements, aligning and distributing your layers "by eye" with unexpected accuracy.

Adding guides

To create a guide, press Ctrl+R (

Figure 13.29. The Lock buttons at the top of the Layers palette let you protect certain layer attributes.

Tip

You also can place a guide at a specific location horizontally or vertically, using the View

After you've created your guide or guides (drag as many as you need onto the image), you can use them to align and distribute your layers — against the guides, and against each other, using the guides to establish common vertical and horizontal planes.

To make sure your layers adhere to the guides, Ctrl-drag (Win) or

Figure 13.30. Click and drag from one of the rulers to create a guide, and then Ctrl-drag (

-drag on the Mac) each layer or selection into position.

Note

Single-line text layers snap to horizontal guides a little differently than other kinds of layers. Rather than snapping by the top or bottom edge of the layer, Photoshop snaps a text guide by its baseline. It's just what you need when aligning type.

Figure 13.31. Pink lines flash when something lines up. In this example, we've dragged our moon so that its center is aligned to the top and right edges of the skeleton. Smart Guides are a big help when aligning both horizontally and vertically, with or without ruler-derived guides in use.

For more control over the placement of layers in your image, Photoshop offers a grid, which is a regular series of snapping increments. Think of it like a ton of guides, positioned in uniform increments, and you don't have to drag each of them onto the image, because they all arrive at once when you choose View

You edit the grid in the Guides, Grid, Slices & Count panel of the Preferences dialog box, which you can get to by pressing Ctrl+K and then Ctrl+6 (

Tip

Don't want to see the grid anymore? Choose View

The final method for controlling movements in Photoshop is the Ruler tool. To activate it (it shares a button with the Eyedropper, Color Sampler, and Count tools), Alt-click (Option-click on the Mac) the Eyedropper tool a couple of times to select it, or press Shift+I twice (if the Eyedropper is displayed) to activate the tool.

When the tool's active, all you have to do is click and drag from one point to another point in the image window, and Photoshop itemizes the distance and angle between the two points in the Info palette. The Ruler tool is even smart enough to automatically display the Info palette if it's hidden.

From that point on, anytime you select the Ruler tool in the current image, Photoshop displays the original measurement line. This way, you can measure a distance, edit the image, and press I to refer back to the measurement. If you've switched to the Eyedropper or Color Sampler tool at any point in the interim, Shift+I brings back the Ruler tool.

To measure the distance and angle between two other points, you can draw a new line with the Ruler tool, or drag the endpoints of the existing measurement line.

Figure 13.32. With the grid in place — set by tweaking the Grid Preferences — you have a customizable network of guides you can snap to or not snap to, positioning your layers along the vertical and horizontal lines.

Photoshop accommodates only one measurement line per document. But you can break the line in two using what Adobe calls the "protractor" feature. Alt-drag (Win) or Option-drag (Mac) on one of the endpoints to draw forth a second segment. The Info palette then measures the angle between the two segments. As demonstrated in Figure 13.33, the L1 item in the Info palette lists the length of the first segment, L2 lists the length of the second segment, and A tells the angle between the segments.

Tip

The Ruler tool is great for straightening crooked layers. After drawing a line with the Ruler tool, choose Image

Figure 13.33. Here we have the distance from the center line of the skeleton to that of the moon and the 45-degree angle. The Info palette displays the data and serves as a guide as you drag; it updates as the Ruler tool's lines are drawn and adjusted.

Photoshop has two varieties of transformations. Transformation commands that affect the entire image — including all layers, paths, channels, and so on — are listed in the Image menu. Those that affect layers and selected portions of layers are in the Edit menu or, in the case of selection outlines, in the Select menu.

The following list explains how to apply transformations to every pixel in an image, regardless of whether or not the image is selected:

No command is specifically designed to slant or distort the entire image. In the unlikely event you're keen to do this, you'll have to link all layers and apply one of the commands under the Edit

To transform a selection, a layer, or a collection of linked layers, you can apply one of the commands in the Edit

While you don't have the precision of entering specific measurements into the options bar that displays when you've picked one of the Transform submenu commands, with Free Transform, you can scale, flip, rotate, slant, distort, and move a selection or layer in one continuous operation. This one command lets you get all your transformations exactly right before pressing Enter or Return to apply the final changes. The command is demonstrated on the image shown in Figure 13.34. Each of the elements in this image resides on an independent layer. The blossom layer is active, and the shadow is linked to this layer. Therefore, both blossom and shadow will transform together.

Figure 13.34. This blossom and its shadow reside on separate layers. But because they are linked together, they will transform as one.

Here's how it works: To initiate the command, press Ctrl+T (

Here's how to work in the Free Transform mode:

To tug two opposite corner handles in symmetrical directions, Ctrl+Alt-drag (

Figure 13.36. Press Ctrl and Alt (

and Option) and drag a corner handle to move it and its opposite corner handle in symmetrical directions. The result is a free-form skew.

Note

If the finished effect looks jagged after you've applied the transformation, it's probably because you selected Nearest Neighbor from the Image Interpolation pop-up menu in the Preferences dialog box. To correct this problem, press Ctrl+Z (

Tip

To transform a clone of a layer or selected area, press Alt (Option) when choosing the Free Transform command or press Ctrl+Alt+T (

If no part of the image is selected, you can transform multiple layers at a time by first linking them, as described in the "Linking and unlinking" section earlier in this chapter.

Tip

To replay the last transformation on any layer or selection, choose Edit

Note

Neither Free Transform nor any of the commands in the Edit

The Warp command allows you to totally disfigure (distort is too mild a term for what this feature does, and there's already a Transform

When you grab the edges where the gridlines meet the bounding box, dragging creates the sort of handles you see when drawing Bezier curves with the Pen tool. Also shown in Figure 13.37, these handles let you change the direction and curve of the stretched sides of the grid (and the layer within it, being dragged right along with the grid), pulling it up, down, in, and out.

After you've finished tormenting the layer, all you have to do is press Enter to commit to the transformation, or press Esc to abandon it and send the layer back to its pre-Warp state.

To really go to town on a layer and get some help in shaping the layer at the same time, you can click the Warp drop-down list, shown on the Options bar that appears when you activate the Warp command. Figure 13.38 shows the Options bar list. After a Warp preset has been applied, you can resize the Warp effect and click and drag from the single handle and flip the layer's content by dragging back through the layer itself.

Figure 13.37. Grab any grid intersection, corner, or bounding box handle, and pull, stretch, twist, and generally abuse the selected layer.

The Warp command's Options bar also offers numerical fields into which you can type the Bend (a percentage increase or decrease in it) or a Horizontal or Vertical percentage change, which changes the perspective of the preset Warp. For more about using such numerical transformation tools, keep reading — that's what the next section is all about.

Figure 13.38. Use the Warp tool's Options bar to apply a preset Warp to the layer, and then drag the lone grid handle to resize the layer and change the scale of the layer's distortion.

To track your transformations numerically, display the Info palette (F8) before you apply the Free Transform command. Even after you initiate Free Transform, you can access the Info palette by choosing Window

Figure 13.39. Normally, the options in the Options bar change only when you select a different tool, but choosing Free Transform adds a series of controls that permit you to transform a selection or layer numerically.

For the most part, the controls in the Options bar are straightforward. Click in the grid of nine squares to reposition the transformation origin. Use the X and Y values to change the location of the origin numerically. Click the triangular delta symbol to measure the movement relative to the transformation origin. Use the W and H values to scale the selection or layer. Click the link button to constrain the W and H values and resize the selection or layer proportionally. The angle value rotates; the H and V values skew.

Photoshop gives you the ability to control the values in the Options bar by "scrubbing," or dragging back and forth, over the icons or letters next to the editable values. When you see your mouse pointer turn to a two-headed arrow (at the tip of a pointing finger, labeled in Figure 13.40), you can drag over the position or scale values to increase or decrease them in increments of 1 pixel or 1 percentage point, respectively. Press and hold Alt (Option on the Mac) while scrubbing to change that to .1 pixel (or percentage point), and press and hold Shift to scrub the values in increments of 10. Scrubbing on the more sensitive angle and skew settings, however, raises or lowers them by .1 degree, and adding Shift changes the increment to 1 degree. By the way, at just about every location in Photoshop that you can find a numeric field, you can scrub.

Figure 13.40. Scrubbing values on the Options bar

Probably, most people use the Options bar strictly for scaling and rotating: It's easy to picture the change that your entries into the Width, Height, and Set Rotation fields will do to the layer in question. You'd need the spatial awareness of a NASA navigation system to predict a numerical slant.

As you may recall, further discussion of the Lock Transparency button was promised when first mentioned in the section on locking layers. That further discussion begins here. Now, if you don't remember this, to refresh your memory, the Layers palette, with the Lock Transparency button labeled, appears in Figure 13.41.

Figure 13.41. The Lock Transparency button enables you to paint inside the layer's transparency mask without harming the transparent pixels.

When selected, this button prevents you from painting inside the transparent portions of the layer. And although that may sound like a small thing, it is in fact the most useful Lock option of them all. Suppose you want to paint inside the moon shown in Figure 13.41. If this were a flat, non-layered image, you'd have to draw a selection outline carefully around the moon to isolate it from the other pixels in the image. With layers, however, there's no need to do this, because the moon lies on a different layer than its background, and a permanent selection outline exists because of this, telling Photoshop that there are both transparent and opaque pixels. Further, it tells Photoshop which pixels are which, and this creates the transparency mask.

The first example in Figure 13.42 shows the moon on its own with the background hidden. The transparent areas outside the mask appear in the checkerboard pattern. When the Lock Transparency button is deselected, you can paint anywhere you want inside the layer. Selecting the Lock Transparency button activates the transparency mask and places the checkerboard area off-limits.

The bottom image in Figure 13.42 shows what happens after the Lock Transparency button is selected and the Clone Stamp tool is used to paint in the other content. No matter how large the Clone Stamp was (it was much larger than the moon), the cloned content appears only within the moon's portion of the layer. The transparent areas are protected by the mask.

Some more useful information about Lock Transparency:

In addition to the transparency mask that accompanies every layer (except the background), you can add a mask to a layer to make certain pixels in the layer transparent. Now, you might wonder if simply erasing portions of a layer wouldn't make those portions transparent — and you'd be right, it would. When you erase, however, you delete pixels permanently. By creating a layer mask, you make pixels temporarily transparent instead. You can return at any time in the future and bring those pixels back to life again simply by adjusting the mask. So layer masks add yet another level of flexibility.

To create a layer mask, select the layer you want to mask and choose Layer

To edit the mask, simply paint in the image window. Paint with black to make pixels transparent. Because black represents deselected pixels in an image, it makes these pixels transparent in a layer. Paint with white to make pixels opaque.

Thankfully, Photoshop is smart enough to make the default foreground color in a layer mask white and the default background color black. This ensures that painting with the brush makes pixels opaque, whereas painting with the eraser makes them transparent, just as you would expect.

Figure 13.42. The layered moon as it appears on its own (top) and when content from another image has been clone stamped in with the Lock Transparency button turned on (bottom).

Figure 13.43. The layer mask thumbnail (to right of the moon's layer thumbnail) indicates the presence of a mask. The black areas in the mask translate to transparent pixels in the layer. The gradient to the moon selection makes it appear to fade out along its bottom-left side.

Photoshop offers lots of bells and whistles to make the function of layer masks both convenient and powerful. Here's everything you need to know:

When and if you finish using the mask — you can leave it in force as long as you like — you can choose Layer

One command, Edit

Tip

Once upon a time in Photoshop, there was a command that made it possible to paste a copied image in back of a selection. Although the command is gone, its spirit lives on in — you'll be shocked — a keyboard shortcut. Just press Alt (Win) or Option (Mac) when choosing Edit

About now, you may be getting a little tired of the topic of layer masking. There's one more important facet of this very broad topic left to discuss, and then we'll move on. The facet? You can group multiple layers into something called a clipping mask, in which the lowest layer in the group masks the others. Where the lowest layer, or base layer, is transparent, the other layers are hidden; where the lowest layer is opaque, the contents of the other layers are visible.

You can create a clipping mask in three ways:

When you open a 3D file in Photoshop (File

Figure 13.49. This figure shows an Image Size dialog box for importing an existing 3D image. Because we selected a .3ds file, the title bar for the dialog box repeats the type of content we're importing.

Once that's out of the way, the existing model is placed on its own layer within the file, as shown in Figure 13.50.

Figure 13.50. A 3D layer as seen in the Layers palette

If you already have a file open and want to import a 3D file in to a new layer, just choose Layer

Okay — so you have a 3D layer in your file. Now what? You can't do a whole lot with it at this point — it's just another layer in the stack, and Photoshop's 3D tools are hidden from view. Not a problem — give the layer icon a double-click and the 3D Options bar comes to life. Figure 13.51 shows the results.

Figure 13.51. The Options bar for an active 3D layer

It's important at this stage to understand what you can and can't do to 3D content in Photoshop. You can't edit the physical 3D model itself. For example, you can't turn a model of a banana into a beach ball. And, you can't create new textures and attach them to a model. If you need to do that, then it's back to a 3D authoring application you go. This doesn't mean you can't change various properties of the model. For example, you can modify its position, rotation, lighting, camera properties, and render modes. You also can view the models in cross section, and edit any existing textures the model possesses. And, of course, you can add anything to the composite image Photoshop is capable of — combining multiple 3D objects into a single image, adding 2D layers to the composition, and so forth.

Transforming a 3D model, for our purposes, means moving, rotating, or scaling. We're dealing with 3 dimensions as enacted within a 2-dimensional interface. There are the traditional left and right (the x-axis) and up and down (the y-axis), as well as a perceived front to back (the z-axis). It's the genius of 3D software that reconstructs the image each time we move something to create the illusion of looking out a window onto a 3-dimensional object, when in reality, we're just looking at colored pixels on the face of our monitor. These modifications are done using the six tools on the option bar to the left side of the View menu we showed in Figure 13.51. Simply double-click the 3D layer's icon in the Layers palette to activate the 3D tools Options bar, and then make sure the Edit 3D Object option button (the very first button on the Options bar) is selected. From here, it's just a matter of selecting a tool and modifying the object. Your options are:

You also have a couple of toggles available when using these tools. Say, for example, you're rotating and want to roll the model a tad (or vice versa). Instead of swapping tools, just hold down your Options key (Mac) or Ctrl key (Win). You can use the same technique to toggle between Drag and Slide.

You also can use the Shift key to modify the way the Drag and Slide tools behave. Hold down the Shift key while dragging or sliding, and the tool moves only in the direction you're currently moving the cursor — left and right, or up and down.

If you need numeric accuracy in transforming an object, simply click the small drop arrow to the right of the Scale tool. This displays the Object Position pop-up, shown in Figure 13.52, where you can enter the desired values.

Figure 13.52. Enter numeric values for your transformations in the Object position pop-up.

In the world of 3D imagery, you have the objects themselves, the "lights" that make them visible to us, and the "camera," which provides the view. When using the transformation tools discussed previously, the camera view remains fixed, but you can manipulate this imaginary camera just as you do the 3D objects. Just click the Edit the 3D Camera button on the Options bar to swap in the Camera Tools, and you're ready to go. The 3D Camera tools mirror the 3D Object tools, except now you're moving the camera around the object, as opposed to moving the object around in front of the camera. The tricky thing here is that everything looks pretty much the same — for example, what you see when you rotate the object is exactly what you see when you orbit the camera. It's up to you to pay attention to what tools you're using. With that said, your 3D Camera tools include:

Just as shown earlier, you can set exact numeric values by clicking the small drop arrow, this time to the right of the Zoom tool. A similar pop-up appears (called 3D Camera Settings), and you can enter your desired values, as shown in Figure 13.53.

Figure 13.53. The 3D Camera Settings pop-up. The Orthographic View check box displays the 3D model in accurate scale view while removing perspective distortion.

What's a camera view? You simply move the camera into a new location/orientation with respect to the object, and save that position. The 3D Camera tools already have some preset camera views: Default (the original position of the camera set in the 3D authoring application), and the standard isometric views: Left, Right, Top, Bottom, Back, and Front.

To add a custom camera view, use the 3D Camera tools to position the camera where you'd like, and simply click the Save button (which uses a floppy disk for its icon) found to the right of the View drop menu. This opens the the New 3D View dialog box, where you can enter a name for your view, as shown in Figure 13.54.

Your new view option now appears at the bottom of the View drop menu, in both 3D Object and 3D Camera modes (Figure 13.55).

Figure 13.54. Saving a new view to the View drop-menu

Figure 13.55. Once saved, your view options are available in both 3D Camera and 3D Objects modes.

We mentioned lighting a little while back. In 3D authoring programs, it's the lighting that makes the objects visible. Otherwise, the camera view simply displays black silhouetted objects. Photoshop allows you to change the light settings for the object, giving you a choice of the default lighting created in the 3D authoring program, or a series of presets.

To change the current light settings, first click the Light and Render Mode Options button. This pops up the Light and Appearance settings. From here, click the drop menu under Lighting settings and choose from the list of available presets, as shown in Figure 13.56.

Figure 13.56. The Lights from File option use the lighting effects created in the original authoring program.

You can change the method by which the 3D model is rendered using the Appearance pop-up. When you import the 3D model, its default rendering is solid. To change the render mode, simply select a different option from the Render Mode drop menu. For example, in Figure 13.57 we've changed the rendering mode from Solid to Shaded Wireframe. You then can set Line Color, Face Color, Opacity, and Crease Threshold values, as applicable.

The 3D layer tools allow you to slice and dice models in your 3D layers along each of the three axes, as shown in Figure 13.58. With the 3D tools active on the Options bar, click the Cross Section Settings button to display the corresponding pop-up palette. From here, you need to select the Enable Cross Section check box to activate the rest of the tools there.

Figure 13.57. You have seven possible options on the Render Mode drop menu.

Figure 13.58. You can modify the Alignment, Position, and Orientation of your cross section.

The following options are at your disposal:

Many 3D objects are textured, meaning they've had 2D images applied to their surfaces to provide realism. When you import a 3D model that contains textures, those texture files are displayed in the Layers palette, indented beneath the 3D layer to which they are attached, as shown in Figure 13.59.

While you can't create and attach new textures to a 3D model, you certainly can use every tool in Photoshop's arsenal to edit the existing textures. Just double-click a texture layer in the Layers palette to open the associated text image in a separate document window. Now you can do anything you like to it. Once you've finished, simply save the file and the texture is updated in the 3D model.

Figure 13.59. As with other layer types, textures appear with the traditional Eye icons beside them. Use these to hide or display the textures in your image.