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Applying Transformations
Photoshop treats some kinds of edits differently than others. Edits that affect the geometry of a selection or a layer are known collectively as transformations. These transformations include scaling, rotating, flipping, slanting, and distorting. (Technically, moving is a transformation as well.) Transformations are a special breed of edits in Photoshop because they can affect a selection, a layer, multiple layers, or an entire image at a time.
Transforming the entire image
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 the image is selected or not:
Scale: To resize the image, use Image Image Size. Because this command is one of the most essential low-level functions in the program, I covered it way back in Chapter 3.
Rotate: To rotate the entire image, choose a command from the Image Rotate Canvas submenu. To rotate an image scanned on its side, choose the 90 CW or 90 CCW command. (That's clockwise and counterclockwise, respectively.) Choose 180 to spin the image on its head. To enter some other specific value, choose Image Rotate Canvas Arbitrary.
| Tip | To fix a crooked scanned image, for example, select the measure tool from the eyedropper flyout in the toolbox (press I or Shift+I, depending on your preference settings, three times). Drag along what should be a vertical or horizontal edge in the image. If you like, note the A value in the Info palette. Then choose Image Rotate Canvas Arbitrary. Look, the angle value is preset to the angle you just measured. That Photoshop, it's one sharp cookie. Press Enter or Return and the job's complete. |
Whenever you apply the Arbitrary command, Photoshop has to expand the canvas size to avoid clipping any of your image. This results in background-colored wedges at each of the four corners of the image. You need to either clone with the clone stamp tool to fill in the wedges or clip them away with the crop tool.
Flip: Choose Image Rotate Canvas Flip Horizontal to flip the image so left is right and right is left. To flip the image upside down, choose Image Rotate Canvas Flip Vertical.
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 Transform submenu, as explained in the next section.
Transforming layers and selected pixels
To transform a layer or selection, you can apply one of the commands in the Edit Transform submenu. Nearly a dozen commands are here, all of which you can explore on your own. I'm not copping out; it's just that it's unlikely you'll use any of these commands on a regular basis. They aren't bad, but one command — Free Transform — is infinitely better.
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.To initiate the command, press Ctrl+T (z -T on the Mac) or choose Edit Free Transform. Photoshop surrounds the layer or selection with an eight-handle marquee. You are now in the Free Transform mode, which prevents you from doing anything except transforming the image or canceling the operation.
| Note | You can reach a slightly less powerful version of Free Transform by selecting the move tool and turning on the Show Bounding Box check box in the Options bar. You don't have the ability to adjust the transformation origin, but it can be handy nevertheless. |
Here's how to work in the Free Transform mode:
Scale: Drag one of the eight square handles to scale the image inside the marquee. To scale proportionally, Shift-drag a corner handle. To scale about the central transformation origin (labeled in Figure 12-31), Alt-drag (Win) or Option-drag (Mac) a corner handle.
Figure 12-31: After pressing Ctrl+T (Win) or z -T (Mac) to initiate the Free Transform command, drag outside the marquee to rotate the layer (top). You can also Ctrl+Alt-drag (Win) or z -Option-drag (Mac) a corner handle to move the opposite corner handle symmetrically and skew the layer (bottom).
| Tip | By default, the origin is located in the center of the layer or selection. But you can move it to any place inside the image — even outside the transformation box — by dragging it. The origin snaps to the grid and guides, as well as to the center or any corner of the layer. |
Flip: You can flip the image by dragging one handle past its opposite handle. For example, dragging the left side handle past the right side handle flips the image horizontally.
| Tip | If you want to perform a simple flip, it's generally easier to choose Edit Transform Flip Horizontal or Flip Vertical. Better yet, right-click (Win) or Control-click (Mac) in the image window and choose one of the Flip commands from the shortcut menu. Quite surprisingly, you can choose any of the shortcut menu commands while working in the Free Transform mode. |
Rotate: To rotate the image, drag outside the marquee, as demonstrated in the first example in Figure 12-31. Shift-drag to rotate in 15-degree increments.
Skew: Ctrl-drag (Win) or z -drag (Mac) a side handle (including the top or bottom handle) to slant the image. To constrain the slant, which is useful for producing perspective effects, Ctrl+Shift-drag (Win) or z -Shift-drag (Mac) a side handle.
Distort: You can distort the image by Ctrl-dragging (Win) or z -dragging (Mac) a corner handle. You can tug the image to stretch it in any of four directions.
| Tip | To tug two opposite corner handles in symmetrical directions, Ctrl+Alt-drag (Win) or z -Option-drag (Mac) either of the handles. I show this technique in the second example in Figure 12-31. |
Perspective: For a one-point perspective effect, Ctrl+Shift-drag (Win) or z -Shift-drag (Mac) a corner handle. To move two points in unison, Ctrl+Shift+Alt-drag (Win) or z -Shift-Option-drag (Mac) a corner handle.
Move: Drag inside the marquee to move the image. This is useful when you're trying to align the selection or layer with a background image and you want to make sure the transformations match up properly.
Undo: To undo the last modification without leaving the Free Transform mode altogether, press Ctrl+Z (z -Z on the Mac).
Zoom: You can change the view size by choosing one of the commands in the View menu. You can also use the keyboard zoom shortcuts: Ctrl+spacebar-click, Alt+spacebar-click, Ctrl+plus, or Ctrl+minus on the PC or z -spacebar-click, Option-spacebar-click, z -plus, or z -minus on the Mac.
Apply: Press Enter or Return to apply the final transformation and interpolate the new pixels. You can also double-click inside the marquee or click the check-mark button in the Options bar.
| 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 (z -Z on the Mac) to undo the transformation and then press Ctrl+K (z -K on the Mac) and select the Bicubic option from the General panel of the Preferences dialog box. Then press Ctrl+Shift+T (z -Shift-T on the Mac) to reapply the transformation. |
Cancel: To cancel the Free Transform operation, press Escape, click the "no" symbol button in the Options bar, or press Ctrl+period (z -period on the Mac).
| Tip | To transform a clone of a layer or selected area, press Alt (Win) or Option (Mac) when choosing the Free Transform command or press Ctrl+Alt+T (z -Option-T on the Mac). |
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 layers" section earlier in this chapter. For example, I could have linked the TV and camera layers to transform the two in unison back in Figure 12-31.
| Tip | To replay the last transformation on any layer or selection, choose Edit Transform Again or press Ctrl+Shift+T (z -Shift-T on the Mac). This is a great technique to use if you forgot to link all the layers that you wanted to transform. You can even transform a path or selection outline to match a transformed layer. It's a handy feature. In fact, throw the Alt or Option key in there, and the transformation can be repeated on a clone of the selected layer. |
Numerical transformations
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 Info. You can track the numerical equivalents of your transformations also in the Options bar. Shown in Figure 12-32, the Options bar contains a series of numerical transformation controls anytime you enter the Free Transform mode. These values not only reflect the changes you've made so far, but also permit you to further transform the selection or layer numerically.
Figure 12-32: 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 | Photoshop CS 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. Scrub over the position or scale values to increase or decrease them in increments of 1 pixel or 1 percentage point, respectively. Hold down the Alt key (Option key on the Mac) while scrubbing to change that to .1 pixel (or percentage point), and hold down the Shift key 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. |
I imagine most folks use the Options bar strictly for scaling and rotating. You'd need the spatial awareness of a NASA navigation system to predict a numerical slant.
