PICshopy: Sizing Digital Images

Sizing Digital Images

TIP
Start Out Right:
Digital Cameras

to make lots of choices, but they should be based on where the
image needs to end up. Do not make assumptions when starting a
project. Know the destination of your image so you’ll know which
path to take.

If you’re acquiring a digital image,

be sure to capture enough pixels.

If you want a 5 × 7 inch print and
need 300 dpi, do the math before

Resampling

shooting. Take the inch size and
multiply it by the print resolution.
In this example: 5 × 300 = 1500 and
7× 300 = 2100. Therefore, 1500 ×
2100 = 3,150,000, which is about 3.1

The process of resampling allows you to change the pixel dimen-
sions of your image. This will affect the display and print size
of your image. This part of the resizing process is important for
several reasons:

megapixels. To allow for cropping,
you may want to shoot at an even
higher resolution.

•

•

Images will print faster when they are sized properly for your
output device.
Images will print clearer when you size them to a target size,
and then run a sharpening ﬁlter to enhance the edge detail.

•

Images appear crisper when they are displayed at 100 percent
on a computer screen (such as for a PowerPoint presentation).

The process of resampling is often identiﬁed based on whether you
are scaling the image smaller (downsampling) or larger (upsampling):

•

Downsampling: If you decrease the number of pixels in an im-
age, you are downsampling the image. When you downsample
an image, you permanently discard data. You can specify an in-
terpolation method (discussed in the next section) to determine
how pixels are deleted. After an image has been downsampled
and saved, you cannot restore the discarded data.

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Avoiding Upsampling

•

Upsampling: If you increase the number of pixels in an im-
age, you are upsampling the image. When upsampling, you
create new pixels to expand the image. Again, you can specify

You can avoid the need for up-

an interpolation method to determine how pixels are added.

sampling by scanning or creating
the image at a sufﬁciently high
resolution. If you want to preview
the effects of changing pixel dimen-

When upsampling, you add information that did not previ-
ously exist, which generally just makes a larger image that is
not any sharper than the original.

sions on-screen or to print proofs

at different resolutions, resample a
duplicate of your image.

Choose an Interpolation Method

When you resample an image, Photoshop creates new pixels.
Those new pixels are created based on the neighboring pixels.
How those new pixels are formed is determined by the interpola-

Resampling 41

tion method you specify. Photoshop offers up to ﬁve methods to

resample your image.

Choose one of the following methods:

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Nearest Neighbor: This method is fast but not very precise.
It is useful for resizing illustrations. However, it can produce

jagged edges.

•

Bilinear: This approach uses pixel averaging. It is a balance
of speed and quality, and produces medium-quality results.

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Bicubic: This method is slower but more precise than the
ﬁrst two (and more desirable). Photoshop spends more time

examining surrounding pixels before interpolating new ones.

The math at work is very complex, so this method will produce

smoother results than Nearest Neighbor or Bilinear.

•

Bicubic Smoother: This method is a reﬁnement of Bicubic.
It is speciﬁcally designed for upsampling (enlarging images).

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Bicubic Sharper: This method is also a reﬁnement of Bicubic.
It is useful for downsampling (shrinking images). It does a bet-

ter job of maintaining sharpness than the other methods.

Setting the Default Method

Photoshop allows you to choose

a default interpolation method.

This will be used when you

invoke a sizing command, such

as the Free Transform or Image

Size commands (more on both

in the pages ahead). Choose

the method that best matches

your workﬂow.

1. Choose Edit > Preferences

or press Command/Ctrl+K

to call up the Preferences

dialog box.

2. From the Image Interpolation drop-down menu, choose your

default method (Bicubic is the most ﬂexible method and is

recommended).

3. Click OK.

42 Chapter 4 Sizing Digital Images

Resizing an Image
Many of your images will probably not be sized to the exact di-
mensions you need. You have several options at your disposal. To
change the size of an image, you can use the Image Size or Canvas
Size commands. You can also use the Crop tool or Free Transform
command to make an adjustment. You can use these choices indi-
vidually or in combination to achieve the desired results.

Image Size
The Image Size command lets you permanently reassign the total
pixel count, as well as resolution, for a particular image. You can
also use this command to upsample or downsample an image.
This is an easy way to size an image to a speciﬁc height or width.
Let’s put the command into action:
1. Open the ﬁle Ch04_Flower.tif from the
Chapter 4 folder.
2. Choose Image > Image Size.
The Image Size dialog box offers several
choices. You can choose to manipulate the
pixel dimensions of the image (measured in
pixels or percent). You can also modify the
print size, which is the size of the image when
printed. You can modify the print size based
on percent, inches, centimeters, millimeters,
points, picas, or columns. The most common
choices are percent, inches, or centimeters,
because most users easily understand these

RETURN OF FOCUS

When upsampling an image, you may notice visi-
ble softening. The more you enlarge the image, the
more noticeable it will be. Enlargements greater
than 30 percent can be particularly problematic.
One approach to solving this issue is to sharpen the
image. Applying the Smart Sharpen ﬁlter to a re-
sampled image can help clarify the image details.
You can ﬁnd out more about sharpening images in
Chapter 11, “Repairing and Improving Photos.”

units of measure.
3. Set the Document Size to measure in inches.
Specify a new height of 4 inches.
4. Be sure to select the Resample Image option
if you want to change the pixel dimensions.
Choose the method to Resample Image that
is most appropriate for your image. Bicubic
is the most common method, but you may
have special circumstances. See “Choose an
Interpolation Method” earlier in this chapter.

Resizing an Image 43

5. Leave the Constrain Pro-

portions box selected, or

you will introduce distor-

tion. You generally want to

keep the width and height

constrained to the same

ratio so the image resembles

its original appearance.

6. Click OK.

Canvas Size

The canvas size is your work

area. When you create a new

document, you can specify the
size of your canvas. When you
scan a photo or import a digital

This photo was resized from a height of 6 inches to 4 inches. The reso-
lution of 300 ppi did not change. The image on the right is smaller
because it has fewer total pixels.

image, the canvas size is set to

the edge of the image. You may need to change the canvas size to

crop or extend the canvas of your image to work on speciﬁc areas

of the image. Let’s try it out:

1. Open the ﬁle Ch04_Beach.tif from the Chapter 4 folder.

2. Choose Image > Canvas Size.

When you launch the Canvas Size command,

you’ll see the pixel dimensions of your cur-

rent canvas. You can specify a new canvas

size using a variety of measurements. Pixels

is a useful measurement if you’re creating

screen graphics, whereas inches or centime-

ters is easier to understand for print work.

Let’s place a uniform border around the image.

3. Select the Relative check box. This disre-

gards the numerical values of the current

canvas size and allows you to specify a new

amount to be added to the existing image.

4. Set the anchor point for the image to be centered. This will

expand the border in all directions around the center of the

current image.

44 Chapter 4 Sizing Digital Images

5. Add a quarter-inch border
on all sides. Type .25 inches
into the Width and Height
ﬁelds.
6. Specify a Canvas extension
color. This is the color that
Photoshop places around the
image when you change the
canvas size. You can choose
to use the foreground or
background colors that are
loaded in the toolbox. You
can also use white, black,
gray, or other, which can be
any color you specify. In this
case, choose white.
7. Click OK.

Crop Tool
With the Crop tool you can change a viewer’s
perception of an image. You can choose to
tighten the area of interest of an image, which
allows you to de-emphasize (or even eliminate) parts of a photo
and improve the image by better framing the subject.
You can invoke cropping in two ways. The ﬁrst method involves
making a selection with the Rectangular Marquee tool, and then
choosing Image > Crop. While this works ﬁne, it does not offer as
much control as using the second method, the Crop tool. Let’s put
method two into action:

TIP

1. Open the image Ch04_Riders.tif from the Chapter 4 folder.

Cropping Keyboard Shortcuts

2. Choose the Crop tool from the Tools panel or press C.

•
•

To toggle the shielded area off,
press the forward slash key (/).
To hide the selection border,
press Command/Ctrl+H.

3. With the Crop tool, make a selection to crop the image. In this
case, removing the rider on the far left (who is chopped off)
will improve the composition of the image. Additionally, re-
ducing the headroom (space above the riders’ heads) will also

improve the image’s appearance.

Resizing an Image 45

4. You can reﬁne the crop selection after it is

made. Mouse over an edge of the crop until

the pointer changes to a double-headed ar-

row, then click and drag on the crop selection

border to pull the crop tighter or expand it

looser. Additionally, you can click a corner of

the crop border to expand two sides at once.

5. Examine the crop. Make sure you’ve selected

the Shield check box in the Options bar.

This gives you a better idea of the area to

be cropped.

6. When satisﬁed with the crop, press Return/Enter or click the

Commit button (check mark) in the Options bar. The shielded

(darkened) areas will be cropped. To cancel, press the Esc key.

Power crop

It is possible to crop and resize an image at the same time. I refer
to this technique as a power crop, and it is a huge time-saver. Before
cropping, you can type the desired size of your ﬁnal image into

TIP
Restoring Hidden Pixels

the Options bar. When you drag to crop the image, your box will
constrain to the proper aspect ratio. This allows you to resize and
crop in one step.

With Photoshop CS4, you can
choose Image > Reveal All to restore
all hidden pixels if you’ve used the
Hide method for cropping.

Let’s crop an image to a 4-inch

by 4-inch square at 200 ppi.

1. Open the ﬁle Ch04_Night_

Street.tif.

2. In the Options bar, type 4

in (as in inches ) into both the

Width and Height ﬁelds.

3. In the resolution ﬁeld, type

200 and set it to pixels/inch.

4. Drag to crop the image.

Your crop selection is con-

strained to the shape you

speciﬁed in the Options bar.

46 Chapter 4 Sizing Digital Images

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VIDEO
TRAINING
Power Crop

VIDEO
TRAINING
Nondestructive Cropping

5. Click the Commit button or press Return/Enter. When ﬁn-
ished cropping, you may want to click Clear to reset the tool’s
default settings.

Nondestructive cropping
Cropping is very important, but it’s also permanent. When you
crop an image, you permanently discard data. Nondestructive
editing is a workaround that allows you to crop an image and keep
the cropped pixels available for future use. Nondestructive editing
provides you with ﬂexibility throughout the design process. Let’s
put the technique to the test:

1. Open the image Ch04_Nondestructive.tif
from the Chapter 4 folder.
2. To crop nondestructively, you must convert
the Background into a standard layer. You’ll
explore layers in depth in Chapter 8, “Com-
positing with Layers.” For now, double-click
the word Background in the Layers panel.
Name the layer Car and click OK.
3. Select the Crop tool by pressing C.
4. Mark out an area to crop.
5. In the Options bar, change the Cropped Area
to Hide (Delete is selected by default).

Resizing an Image 47

6. Click the Commit button or press Return/

Enter.

7. Select the Move tool by pressing V (as in

moVe, the letter M is used by the Marquee

tool). Drag in the image and reposition it; the

original pixels are still available, allowing

you to modify the crop in the future.

Perspective cropping

Some images will have visible distortion, which

is often caused by the camera not being square

with the subject. If the photographer was higher

(or lower) than the image or if the photo was tak-

Because the cropped pixels were hidden (instead of deleted),

en at an angle, you will see distortion. In some
cases, this distortion is part of the shot composi-
tion and is desirable. In others, the distortion can

details were preserved outside the cropped area. This allows
for the image to be repositioned within the frame. Be sure
to save the image as a PSD ﬁle or Layered TIFF to preserve
future ﬂexibility.

be distracting. Let’s square off an image:

1. Open the ﬁle Ch04_Per-

spective.tif from the Chap-

ter 4 folder.

2. Select the Crop tool by

pressing C.

3. Crop around the window

in the photo as tight as you

can to frame it.

4. In the Options bar, set the

Crop to Delete, not Hide.

Then select the Perspective

check box.

5. Click the Shield Color to

select a new color. In the

Color Picker, select a bright

red to make it easier to see the cropped area.

6. Drag the upper-right and upper-left corners in toward the
center. You are trying to line up the crop borders parallel to
the edge of the window. The crop selection will no longer look

11

VIDEO
TRAINING
Perspective Cropping

rectangular.

48 Chapter 4 Sizing Digital Images

7. Click the Commit button or press Return/
Enter. The resulting image should appear
as if the photo was squared and the camera
was level.

Rotate Canvas Command
Sometimes your image will need to be rotated or
ﬂipped. Loading your image upside down on the
scanner, loading a slide backwards into a slide
scanner, or turning the camera on its side when
taking a portrait often causes inverted or reverse
images. You may also want to make a change to
your image for compositional purposes.
The Rotate Canvas command offers several
choices. You can choose to rotate the image 180˚
(half a rotation), 90˚ clockwise or counterclock-
wise, or an arbitrary amount (the user types in a
number of degrees). Additionally, the entire can-
vas can be ﬂipped (creating a mirrored image).
You can choose to ﬂip the canvas horizontally
or vertically:
1. Open the image Ch04_Ro-
tate.tif from the Chapter 4
folder.
2. Choose Image > Rotate
Canvas 90˚ CCW (coun-
terclockwise). The image is
now properly oriented.

Free Transform Command
The Free Transform command is another useful way to rotate
and size an image. It works best when you have an object located
on its own layer or if you have an active selection. You’ll explore
selections and layers in much greater detail in future chapters.
For now, let’s work with a simple layered image that has already
been prepped.

Resizing an Image 49

1. Open the ﬁle Ch04_Free_Transform_

Basic.psd.

2. This image has two layers: a background,

which is a gradient, and a vector shape layer.

A vector layer is a special layer in Photoshop.

It can be resized and transformed repeatedly

with no degradation in quality. Vector layers

use math to describe curves and can be freely

manipulated.

3. If it’s not visible, call up the Layers panel by

selecting Windows > Layers.

4. Select the Vector Shape layer so it is active.

5. Choose Edit > Free Transform or press Command/Ctrl+T.

You can access several controls for the Free Transform command

by right-clicking/Control-clicking. Try the following transforma-

tions on the Vector Shape layer. You can press the Esc key to

cancel the transformation or Return/Enter to apply it.

•

Scale: You can scale by dragging a handle. Hold down the
Shift key as you drag a corner handle to scale proportionately.
Hold down the Option/Alt key to scale in both directions

12

VIDEO
TRAINING
Free Transform Command

simultaneously. To scale numerically, enter a value in the

Options bar.

•

Rotate: You can choose to rotate a preset amount by select-
ing Rotate 180˚, Rotate 90˚ CW, or Rotate 90˚ CCW. To rotate

freely by dragging, move your mouse outside

the Free Transform box. It will become a

curved, two-headed arrow. Hold down the

Shift key while rotating to constrain the rota-

tion to 15° increments. Additionally, you can

rotate numerically by entering degrees in the

rotation box in the Options bar.

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Skew: Skewing an image creates a sense
of distortion, as if the image were leaning.

To skew the image, hold down Command/

Ctrl+Shift and drag a side handle (not a

corner handle). The cursor will change to a

white arrowhead with a small double arrow.

50 Chapter 4 Sizing Digital Images

•

•

Distort: If you want to distort an image freely, choose Distort.
This allows you to move the corners of the image freely (a process
also known as corner-pinning). You can also access this com-
mand by pressing Command/Ctrl while dragging a corner point.
Perspective: Transforming perspective creates the il-
lusion that the image is being viewed from above or
from the side. You can access this command by pressing
Command+Option+Shift/Ctrl+Alt+Shift or from the context
menu. This is a useful command to ﬁx perspective problems or
to add perspective effects.

•

•

Warp: The Warp command was ﬁrst intro-
duced in Photoshop CS2. It allows you to
distort an image into a number of predeﬁned
shapes available in the Options bar (such as
Arch, Flag, or Twist). By choosing Custom,
several points can be freely dragged to distort
the image as desired.
Flip Horizontal and Flip Vertical: These
simple commands let you ﬂip an individual
layer without ﬂipping the entire canvas.

The Free Transform command
has one major beneﬁt over
choosing individual transform
commands from the Image
menu: Free Transform lets
you apply transformations
in one continuous operation,
which reduces quality loss in
raster images.

Open the ﬁle Ch04_Free_Transform_Additional.psd. Using the Free Transform

command, you can rotate, size, and ﬂip the images to create a better layout.

Resizing an Image 51

Using Smart Objects Before Transforming

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Adobe launched a new technology with Photoshop CS2 called

Smarter Smart Objects

Smart Objects. This powerful command allows you to embed ras-

When using Photoshop CS4, you

ter or vector data into a layer. The layer can then be transformed

can now apply perspective transfor-

indeﬁnitely because the embedded data remains editable and scal-

mations to Smart Objects as well.

able. You can convert one or more layers into a new Smart Object.

Simply follow the instruction in the

A Smart Object is simply one ﬁle embedded inside another. This

“Free Transform Command” section
earlier in this chapter.

can be very useful because Smart Objects allow greater ﬂexibility

than simply applying the Free Transform command to a regular

layer. With a Smart Object, you can perform multiple nondestruc-

tive transforms with no loss in quality (as long as you don’t exceed

the pixel dimensions of the original raster object).

1. Open the ﬁle Ch04_Smart_

Object.psd from the Chap-

ter 4 folder.

2. Select the layer City in the

Layers panel.

3. Choose Layer > Smart

Objects > Group into New

Smart Object.

4. Invoke the Free Transform

command and scale down

the image to a very small

size. Apply the transfor-

mation.

5. Invoke the Free Transform

command and scale up the

image to its original size.

Apply the transformation. Notice that the image remains clear.

When you place a vector object into Photoshop (such as an Adobe

Illustrator or EPS ﬁle), it will automatically come in as a Smart

Object. Additionally, you can choose Layer > Smart Objects >

Group into New Smart Object for raster-based layers.

52 Chapter 4 Sizing Digital Images

TOOL PRESETS SAVE TIME

If you have a speciﬁc image size that you use often, harness the power
of Photoshop’s Preset Manager. You can create tool presets that already
have the values for a tool loaded.

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VIDEO
TRAINING
Smart Objects

1. Type a desired size and resolution into the Options bar.
2. When the Crop tool is selected, you’ll see its icon in the upper-left
corner of the Options bar. Click the triangle to access the drop-down
menu.
3. You’ll see several preset sizes that are stored in Photoshop. Select
the Current Tool Only check box to narrow the presets.
4. Click the Create new tool preset icon in the drop-down menu
(it looks like a pad of paper).
5. Photoshop stores the preset crop size in a temporary
preferences ﬁle.
6. To permanently save cropping sizes, click the submenu icon in the
drop-down menu (the small triangle in a circle). Choose Save Tool
Presets, and save them in a desired location.

Selection Tools
and Techniques

If you really want to get things done in Photoshop, you have to be

5

good at making selections. You might want to remove an object

from a picture or maybe change the sky to another shade of blue?

Or, maybe the sweater in your advertisement needs to be orange

instead of red, or you’d like to duplicate some of the background

crowd so your photo doesn’t look so empty. In each case, you’ll

need an accurate selection.

Why? You may be able to look

at a digital image and clearly

recognize that it’s a brown bear

sitting on a rock ledge, but your

computer just sees a bunch of

pixels. A little human interven-

tion is necessary to distinguish

which part of the image you

want to manipulate or process.

While this means extra effort, it

also means that much of digital

imaging requires human inter-

vention (which means jobs for

designers and artists). Accurate

selections are important, and
there are several techniques

While your eye can easily distinguish between the bear and the background in this
photo, Photoshop just recognizes pixels. It will take some human intervention to

you can employ to get them

make an accurate selection of the bear.

just right. Some are easier than

others, and some are more accurate. Knowing several techniques

lets you make an accurate selection no matter what your source

image looks like.