Photoshop

Retouching and Editing

Transformations

Transformations such as scaling, rotating and skewing can be applied to selected pixels, an entire layer (unless locked), linked layers, and vector shapes. In the Selections module, you learned how to transform a selection border by manipulating the handles of a bounding box. Many of the object transformations work the same way. The difference between transforming only the selection border versus the border and the pixels inside it is the menu command used to apply the Transform bounding box. The ones we'll be looking at in this lecture are in the Edit > Transform submenu. There are also rotate and flip commands in the Image > Rotate Canvas submenu that will apply to the entire image.

When a transformation is applied, the pixels will be remapped using the interpolation method specified in the General Preferences. Bicubic will yield the best results.

Practice Exercise: Transformations

Let's try out these commands so you feel comfortable using them.

  1. Open a new image document that is 500x500 and has a white background. We're not going to save this at the end of the exercise so you don't need to name it.
  2. Open pencil.eps. In the Rasterize Generic EPS Format dialog, make sure Constrain Proportions is checked and set the Width to 400. Mode should be RGB Colour and Anti-aliased should be checked. Click OK.
  3. Drag the layer containing the pencil into the new document.
  4. Close pencil.eps without saving it.
  5. Duplicate the layer with the pencil and hide the layer containing the original. You can use the original during the exercise if you want to start over with an unmodified version of the pencil.

Commit and Cancel Buttons

Commit and Cancel buttons The Commit and Cancel buttons from Photoshop 6.0 (left) and 7.0 (right) are shown here. The Commit button (check mark icon) applies the transformation and is equivalent to pressing Enter (Return). The Cancel button discards any transformation you may have made and removes the bounding box. It is equivalent to pressing the Esc key.

Scale

An object's width and/or height can be modified using the Scale command.

  1. Go to Edit > Transform > Scale.

Transform Scale bounding box

A bounding box with eight handles appears around the pencil. (Only five are shown here.) A handle can be dragged to alter the dimensions of the pencil. The image above shows part of the bounding box and illustrates what dimension(s) each handle controls. A double-headed arrow icon will be displayed when you hold the pointer over a handle. The direction of the icon indicates which dimension will be affected by the transformation.

  1. Click and drag on one of the height handles to resize the bounding box. Once you release the mouse button, the pencil resizes to fill the box.
  2. Drag on one of the width handles.
  3. Press Ctrl-Z (Cmd-Z) to Undo. This will reverse the previous width change but leaves the height change intact.
  4. Drag any corner handle and notice that you can change the proportions of the pencil freely.
  5. To apply these transformations, press the Enter (Return) key or click on the Commit button in the Tool Options bar.
  6. Undo the entire transformation with Ctrl-Z (Cmd-Z).
  7. Go to Edit > Transform > Scale again.
  8. Drag on a corner handle but this time hold down the Shift key while you are doing so. This will retain the proportions of the pencil as you scale.
  9. Press Enter (Return) to apply the scale transformation.

Skew

horizontal and vertical skewing

Skewing an object will let you move one side of the bounding box in two directions. A horizontal side can be moved left or right and a vertical side can be moved up or down. This is normally what the term skew implies. In Photoshop, you can also move a corner handle independently while skewing.

  1. Go to Edit > Transform > Skew.

bounding box for Skew transform

The bounding box looks the same but when you move the pointer over the handles, different icons appear for skewing.

  1. Click and drag on the middle handle on the right side of the bounding box to skew vertically.
  2. Press Enter (Return) to apply the transformation.
  3. Undo.
  4. Choose the Skew command again. This time, drag the bottom right handle downwards to see what happens.

skewing in one direction only

Dragging side handles will move both adjacent corner handles in unison. Dragging by a corner handle will let you move it independently.

  1. Press the Esc key or click on the Cancel button to cancel this transformation.

Distort

The Distort command lets you freely drag any bounding box handle in any direction.

  1. Go to Edit > Transform > Distort.
  2. Try dragging a corner handle around. You'll notice that the direction isn't constrained as it was with the corner handle for skewing.
  3. Try dragging a middle handle around. This moves the adjacent corner points in unison but you aren't constrained in the direction you can drag the handle.
  4. Press the Esc key or click on the Cancel button to cancel this transformation.

Perspective

perspective examples

A perspective transformation will let you apply a perspective effect to an object. You can use it in photos of buildings, for example, to correct the perspective distortion that often occurs in images of that type.

  1. Go to Edit > Transform > Perspective.
  2. Drag the lower right corner handle downward. You'll see the upper right handle moving in the opposite direction.
  3. Undo that and drag the same handle to the right. The lower left handle will move in the opposition direction. Perspective applies an equal amount of distortion to the handle opposite from the direction in which you're dragging. The middle handles on the Perspective bounding box performs skews.
  4. Press the Esc key or click on the Cancel button to cancel this transformation.

Rotate

centre point of bounding box An object can be rotated freely around its centre point or reference point. This point can be moved by dragging it to any location in the image.

Rotate pointer iconThe pointer will display the Rotate icon.

  1. Go to Edit > Transform > Rotate.
  2. Drag anywhere in the image to rotate the pencil.
  3. Hold down the Shift key as you drag. The bounding box will snap to 15o increments.
  4. Press Enter (Return) to apply the rotation.
  5. Go to Edit > Transform > Rotate again and drag the reference point of the bounding box to any location in the image. It will snap to all of the handles. You can drag it outside of the bounding box as well. Once you've dragged it to another location, try rotating the pencil around the new reference point.
  6. Apply the transformation.

Rotate Presets

The Edit > Transform submenu has three rotate presets you can use:

  1. Try using one of these commands. No bounding box appears with these and the Flip commands. The transformation is applied immediately.

Flip

Flip Vertical and Flip Horizontal

The Flip commands let you mirror an object in either a horizontal or vertical direction.

  1. Go to Edit > Transform > Flip Horizontal.
  2. Now try Edit > Transform > Flip Vertical.

Free Transform

Instead of having to use menu commands to transform there is a single command you can use to set up a bounding box that will let you scale, rotate, skew, apply perspective, and distort. You can go to Edit > Transform or use the keyboard shortcut Ctrl-T (Cmd-T). The descriptions and pointer icons were covered in the Selections section but we'll repeat it here for your convenience.

Free Transform
Horizontal Scale icon Horizontal Scale: When the cursor displays this icon, dragging left or right will alter the width of the bounding box.
Vertical Scale Icon Vertical Scale: Dragging up or down will modify the height of the bounding box.
Scale icon Scale: Scaling will modify the width and height at the same time. If you want to retain the width-to-height ratio of the bounding box as you scale, hold down the Shift key while dragging.
Rotate icon Rotate: The bounding box can be rotated freehand by dragging when this icon is displayed. It will appear when the cursor is outside the bounding box. To constrain the rotation to increments of 15o, hold down the Shift key while dragging. The bounding box will rotate around its centre point. You can drag the centre point to another location if you want to rotate around a different point in the image.
Skew icon Skew: The Skew icon will only appear if you press Ctrl-Shift (Cmd-Shift) while you're holding the pointer over one of the four sides of the bounding box. This will apply a horizontal or vertical skew depending on which direction the arrow icon is pointing. Skewing will move one side of the bounding box in the direction you drag while the opposite side of the bounding box will remain in place.
Perspective icon Perspective: The Perspective icon will only appear if you press Ctrl-Alt-Shift (Cmd-Opt-Shift) while you're holding the pointer over one of the four sides of the bounding box. Perspective will expand or contract two adjacent corners of the bounding box.
  1. Select the Move tool.
  2. Press Ctrl-T (Cmd-T) to apply the Free Transform bounding box. Rotate the object and release the mouse button. Move the pointer around inside the bounding box. The Move tool icon will be displayed except if you get too close to the bounding box. You can drag the pencil while the bounding box is active if you've selected the Move tool beforehand. If you try to switch tools while there is an active bounding box, you'll be prompted with "Apply the transformation?" Many menu commands and the tools are unavailable during a transformation. You have to exit before selecting them.
  3. Reposition the pencil in the image by dragging it to another location.
  4. Press the Esc key to cancel the transformation.
  5. Hold down the Alt (Option) key while using the Ctrl-T (Cmd-T) command to set up a bounding box.
  6. Press Shift and rotate the pencil by 15o. A copy of the pencil has been created on a new layer and rotated by 15o, leaving the original pencil layer intact. You can copy and free transform using the menu commands by holding the Alt (Option) key while going to Edit > Free Transform.
  7. Apply the transformation to the copy.

Transform Again

This command will apply the most recent transformation again. It can be accessed by going to Edit > Transform > Transform Again or by using the keyboard shortcut Shift-Ctrl-T (Shift-Cmd-T).

  1. Use the keyboard shortcut Shift-Ctrl-T (Shift-Cmd-T). The pencil copy will rotate another 15o automatically.
  2. Try applying two transformations to the object. For example, after using the Ctrl-T (Cmd-T) shortcut, scale and then rotate the pencil then press Enter (Return) to apply the changes.
  3. Press Shift-Ctrl-T (Shift-Cmd-T) and both transformations will be applied to pencil copy again.
  4. You can close the file without saving.

Transform Options

Once a Transform bounding box is active, the Tool Options bar displays options that give you information about the current object and lets you apply precise values in making transformations.

Reference Point Location

The reference point is just a more descriptive name for the centre point because it can be located anywhere inside or outside the bounding box. Transformations are always applied using the reference point as an anchor point.

reference point location The icon shown on the Tool Options bar is a representation of the bounding box. The active reference point is indicated by the black square. By default, the reference point is at the centre. You can click on the outer squares to set the reference point to a side or corner handle.

Reference Point Coordinates

reference point coordinates The X and Y values display the horizontal and vertical coordinates of the reference point from the 0,0 value of the rulers. You can precisely position the object by entering new values in these fields.

Numeric Scale

numeric scale The W(idth) and H(eight) fields display the dimensions of the bounding box and its contents as percentage values. You can enter new values to scale the object rather than scaling by dragging the bounding box handles.

The link icon between the H and W values is the Maintain Aspect Ratio button. By default, it is disabled so you can change the height and width independently. Clicking on the button will link the two values so that a change to one value will automatically change the other field to the same value. This applies to numeric scaling as well as when you drag a corner handle of the bounding box to scale.

Numeric Rotation

numeric rotation The numeric rotation field can be used to view the current angle of rotation or you can enter a new value to set a precise angle. Positive (clockwise rotation) or negative (counter-clockwise rotation) values can be entered here.

Numeric Skew

numeric skew The angles of horizontal and vertical skew are displayed in these fields and you can set the values manually. Positive or negative values can be entered here.

Transformations Summary

Transformations Keyboard Shortcuts:


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