Sử dụng photoshop cs5 part 20 pdf

CAny added canvas area will auto-matically be filled with the color you chose in the preceding step, unless the image contains layers but not a Background, in which case the added canvas

Changing the canvas size

By using the Canvas Size command, you can

enlarge or shrink a document’s live, editable area

Pixels can be added to or removed from one, two,

three, or all four sides of the image This is useful,

say, if you want to make room for type, as in the

example shown on this page, or to accommodate

imagery from other documents (see Chapter 14)

To change the canvas size:

1 Choose Image > Canvas Size (Ctrl-Alt-C/

Cmd-Option-C) The Canvas Size dialog opens

2 Optional: Choose a different unit of measure

from the Width menu

3. Do either of the following:

Enter new Width and/or Height values The

dimensions are independent of one another;

changing one won’t affect the other.A–B

Check Relative, then in the Width and Height

fields, enter positive values to increase those

dimensions or negative values to decrease them

4 Optional: The gray square in the center of the

Anchor arrows represents the existing image area Click an arrow to reposition the image rel-ative to the canvas The arrows point to where the new canvas area will be added

5 From the Canvas Extension Color menu,

choose a color for the added pixels Or to choose a custom color, choose Other or click the color square next to the menu, then click

a color in the Color Picker (see page 186) or

in the document window If the image doesn’t have a Background (take a peek at the Layers panel), this menu won’t be available

6 Click OK CAny added canvas area will auto-matically be filled with the color you chose in the preceding step, unless the image contains layers but not a Background, in which case the added canvas area will be transparent

➤ You can also enlarge the canvas area manually

by dragging with the Crop tool (see page 129)

A This is the original image.

C After adding pixels to the top of the canvas,

we created some editable type.

B To add canvas area to the top of the image, in the Canvas

Size dialog, we increased the Height value, then clicked the

bottom Anchor arrow to move the gray square downward.

Cropping an image

You can crop an image by using the Crop tool,

the Crop command, or the Trim command We’ll

show you how to use the Crop tool first

To crop an image using a marquee:

1 Choose the Crop tool (C or Shift-C)

2 Drag a marquee over the part of the image

you want to keep.A

3. On the Options bar, do the following:

If the document contains image layers, click

Cropped Area: Delete to have Photoshop

delete the cropped-out areas, or click Hide

to save them with the file (they will extend

beyond the visible canvas area but can be

moved back into view with the Move tool)

Areas outside the crop marquee on the

Background will be deleted, not hidden

Check Shield to darken the area outside the

crop marquee temporarily (to help you see

what will remain after cropping) If desired, you

can change the shield color or Opacity value

4 Perform any of these optional steps:

To resize the marquee, drag any handle

(double-arrow pointer) You can Shift-drag a

corner handle to preserve the proportions of

the marquee and/or hold down Alt/Option to

resize the marquee from its center

To reposition the marquee, drag inside it.

To rotate the marquee, position the cursor just

outside it ( pointer), then drag in a circ ular

direction (you can straighten a crooked photo

this way) To change the axis point around

which the marquee rotates, drag the reference

point away from the center of the marquee

before rotating it The image orientation will

change after the next step

5 To accept the crop, either press Enter/Return

or double-click inside the marquee.B

➤ To cancel a crop marquee, press Esc, or

right-click in the document and choose Cancel

➤ To correct perspective problems, we

recom-mend using the Lens Correction filter (which

is discussed on pages 292–293) instead of the

Perspective option for the Crop tool

➤ To specify a default Image Interpolation

method for Photoshop features, such as the

Crop tool, see page 386

A With the Crop tool, drag a marquee over the portion of the image you want to keep, then accept the crop.

B The image is cropped.

REMEMBER TO RESHARPEN YOUR DOCUMENT AFTER CROPPING IT

Cropping can make an image slightly blurry,

so be sure to apply a sharpening fi lter after-ward See pages 296–300

Next, we’ll show you how to either crop an image

to a specific size (such as a standard photo print) or

crop it based on the dimensions of another image

To crop an image to a specific size or to the

dimensions of another image:

1 Open an image, and choose the Crop tool

(C or Shift-C)

2. Do either of the following:

On the Options bar, enter specific Width and

Height values for the final image You can click

the Swap Width and Height button to switch

the current values

To crop using the Width, Height, and Resolution

values from another image, open that

docu-ment and click its tab Click Front Image on the

Options bar, then click the tab for the document

to be cropped

3 Drag a crop marquee on the image (without

holding down any modifier keys).A You can drag

inside the marquee to reposition it

4. To accept the crop, either press Enter/Return or

double-click inside the marquee.B

➤ To empty the Width, Height, and Resolution

fields on the Options bar for the Crop tool, click

Clear

➤ To create presets for the Crop tool, see our

instructions for creating tool presets on page 402

A After choosing the Crop tool, we entered a Width of 6"

and a Height of 4" on the Options bar, then dragged in the

document to create a marquee.

CROPPING BASED ON THE RULE OF THIRDS ★ The rule of thirds is a guideline that photographers sometimes follow for composing a composition, either when shooting a scene or when cropping it afterward

In Photoshop, draw a marquee with the Crop tool, then choose Crop Guide Overlay: Rule of Thirds from the Options bar Grid lines will appear within the crop marquee Drag the marquee or resize it, positioning the key features of the scene where the lines intersect You can position those features at a pair of diagonal loca-tions (see the colored circles we placed on the image below), or in a landscape, you could position the horizon along either one of the horizontal lines Note:

Although the rule of thirds often works like a charm, you don’t have to adhere to it slavishly

B This image was cropped to a standard photo size of 6 x 4 inches, which you can verify by looking at the rulers.

When you draw a crop marquee that is larger than

the image, the canvas size is increased Unlike the

Canvas Size command, this technique gives you

manual control over how much canvas area is added

and where Another use for this technique is to reveal

imagery that extends beyond the live canvas area

To enlarge the canvas area with the

Crop tool:

1 Choose a Background color (see Chapter 11).

2. To reveal more of the work canvas (gray area)

around the image, either enlarge the document

window or Application frame by dragging a side

or corner, or lower the zoom level of your

document

3 Choose the Crop tool (C or Shift-C)

4. Drag a crop marquee to the edges of the image

5 Drag a corner or midpoint handle of the marquee

into the work canvas (outside the live canvas

area).A

6 To accept the crop, either press Enter/Return or

double-click inside the marquee.B

If the image has a Back ground (look on the

Layers panel), the added canvas area will fill with

the current Background color If the image

con-tains layers but no Background, the added canvas

area will fill with transparent pixels

Note: Pixels on any layer that were formerly

hidden outside the live canvas area may now fall

within it, and will now be visible

OVERRIDING THE SNAP

Normally, if you resize a crop marquee near the edge

of the canvas area and View > Snap To > Document

Bounds is on, the marquee snaps to the edge of the

canvas area If you want to crop slightly inside or

outside the edge of the canvas, you’ll need to override

the snap function Do either of the following: Turn

the Snap To > Document Bounds feature off; or start

dragging one of the handles of the marquee, then hold

down Ctrl/Control and continue to drag

B When we accepted the crop, the added canvas pixels filled automatically with brown, which was the current Background color.

A Drag any of the crop marquee handles outside the canvas area and into the work canvas Here, we’re dragging a mid-point handle to the right to add more canvas area to that side of the image.

Although the Crop command, discussed below, is

simple and straightforward, it doesn’t offer as many

options as the Crop tool does

To crop an image using the Crop command:

1 Choose the Rectangular Marquee tool (M or

Shift-M)

2. Do one of the following:

Drag a marquee over the part of the image you

want to keep.A

To constrain the proportions of the marquee to a

width-to-height ratio, on the Options bar, choose

Style: Fixed Ratio, enter Width to Height values

(such as 1 to 2), then drag in the image

To draw a marquee of a specific size (such as a

standard-size photo print), choose Style: Fixed

Size, enter Width and Height values, then click

in the document You can move the marquee

3. Optional: To scale the marquee, right-click in

the document and choose Transform Selection,

Shift-drag a corner handle, then double-click

inside the marquee to accept the edit

4 Choose Image > Crop, then deselect (Ctrl-D/

Cmd-D).B

➤ If you chose the Fixed Ratio or Fixed Size style

for the Rectangular Marquee tool, reset the tool

by choosing Style: Normal from the Options bar

The Trim command trims away any excess

transpar-ent or solid-color areas from the border of an image

Of course, the end result is still a rectangular image

To trim areas from around an image:

1 Choose Image > Trim

2 In the Trim dialog, click a Based On option:

Transparent Pixels trims transparent pixels

from the edges of the Background If Photoshop

doesn’t detect any such areas in the image, this

option isn’t available

Top Left Pixel Color removes any border areas

that match the color of the left uppermost pixel

in the image

Bottom Right Pixel Color removes any border

areas that match the color of the bottommost

right pixel in the image

3 Check which areas of the image you want the

command to Trim Away: Top, Bottom, Left,

and/or Right.

4 Click OK.

A With the Rectangular Marquee tool, a marquee is drawn over the area of the image we want to keep.

B This is the result after we chose Image > Crop.

Follow these instructions if you need to preserve

the existing width-to-height ratio of an image as you

crop it

To crop an image according to its existing

aspect ratio:

1 With an image open, choose the Crop tool

(C or Shift-C)

2 Drag a marquee diagonally across the entire

image, from one corner to the opposite corner

3 Shift-drag a corner handle on the crop marquee

to resize the marquee proportionately to the

desired crop size

4 Optional: Drag within the marquee to reposition

it over the portion of the image you want to

keep.A

5 To accept the crop, either press Enter/Return or

double-click inside the marquee.B

Flipping or rotating an image

You can flip all the layers in an image to create a

mirror image, or flip just one layer at a time (You’ll

learn all about layers in the next chapter.)

To flip an image or a layer:

Do either of the following:

To flip all the layers, choose Image > Image

Rotation > Flip Canvas Horizontal or Flip

Canvas Vertical C

To flip just one layer at a time, click that layer,

then choose Edit > Transform > Flip Horizontal

or Flip Vertical Any layers that are linked to the

selected layer or layers will also flip

➤ If you’ve flipped a whole image that contains

type, don’t flip out! To make the type readable

again, “unflip” the type layer by using the Flip

Horizontal command

C Here, we chose the Flip Canvas Horizontal command (compare this image with the original one in Figure B).

B We accepted the crop The original width-to-height ratio

of the image was preserved.

A After dragging a marquee across the entire image with the Crop tool, we Shift-dragged a handle, then moved the marquee over the area we want to keep.

The Image Rotation commands rotate all the layers

in an image (To rotate just one layer at a time, use a

rotate command on the Edit > Transform submenu.)

To rotate an image:

Do either of the following:

Choose Image > Image Rotation > 180°, 90° CW

(clockwise), or 90° CCW (counterclockwise).

Choose Image > Image Rotation > Arbitrary.

Enter an Angle value, click °CW (clockwise) or

°CCW (counterclockwise), then click OK.

Straightening a crooked image

When used with its Straighten option, the Ruler tool

squares off a crooked image based on a line you drag

and also crops the image to remove any blank canvas

areas that result around its borders

To straighten a crooked image: ★

1 Choose the Ruler tool (I or Shift-I)

2 Drag along a feature in the image that you want

to orient horizontally or vertically.AIf you

need to adjust the line, move either endpoint

The current angle is listed as the A value on the

Options bar

3 On the Options bar, click Straighten B Easy!

➤ To straighten an image without cropping it, hold

down Alt/Option as you click Straighten and

until the command is done processing

IT CROPS! IT STRAIGHTENS!

File > Automate > Crop and Straighten Photos locates

rectangular areas in a document, rotates and crops

those areas to square them off (if necessary), then

opens each one as a new document Note: This action

isn’t as smart as you are, so it can be fooled; see the

suggestions and precautions below

➤ Use the action to unrotate a Photoshop document

that was previously rotated Apply it to imagery that

doesn’t contain much white in the background, and

click the Background on the Layers panel fi rst

➤ Scan multiple photos at a time and let the action

sort them into individual documents To help it do a

proper job, don’t let the photos overlap one another

or hang off the side of the scanner

➤ To control which area is cropped and straightened,

select that area, including some extra pixels, then

choose the command while holding down Alt/Option B The command reoriented the image along the angle

we defined and cropped away the blank canvas areas.

A This image is slightly askew We dragged with the Ruler tool from top to bottom along one of the col-umns, then clicked Straighten on the Options bar.