Photoshop 6 for Windows Bible- P13 doc

You can select a different portion of the image; click anywhere in the image window with the rectangular marquee tool, the elliptical marquee tool, or the lasso tool; or choose Select ➪

Figure 8-6: Note the results of clicking on a pixel with a brightness

value of 140 (top row) and a brightness value of 10 (bottom row)

with the tolerance set to three different values

Figure 8-7: Because the yellow Sasquatch sign contains almost no blue, it appears

most clearly distinguished from its background in the blue channel So the blue

channel is the easiest channel in which to select the sign with the magic wand

Here’s one more twist to the Tolerance story: The magic wand is affected by theSample Size option that you select for the eyedropper tool If you select PointSample, the wand bases its selection solely on the single pixel that you click But ifyou select 3 by 3 Average or 5 by 5 Average, the wand takes into account 15 or 25pixels, respectively As you can imagine, this option can have a noticeable impact

on the extent of the selection that you get from the wand Try clicking the samespot in your image using each of these Sample Size settings, using the sameTolerance value throughout, to see what I mean

Making the wand see beyond a single layer

The Use All Layers option enables you to create a selection based on pixels fromdifferent layers (see Chapter 12 for more about layers) Returning to my previouslandmass example, suppose you set Europe on one layer and North America on thelayer behind it so the two continents overlap Normally, if you clicked inside Europewith the magic wand, it would select an area inside Europe without extending outinto the area occupied by North America on the other layer Because the wanddoesn’t even see the contents of other layers, anything outside Europe is an emptyvoid We’re talking pre-Columbus Europe here

If you select Use All Layers, though, the situation changes Suddenly, the wand cansee all the layers you can see If you click on Europe, and if North America andEurope contain similar colors, the wand selects across both shapes

Mind you, while the Use All Layers option enables the wand to consider pixels ondifferent layers when creating a selection, it does not permit the wand to actuallyselect images on two separate layers Strange as this may sound, no selection toolcan pull off this feat Every one of the techniques explained in this chapter is appli-cable to only a single layer at a time Use All Layers merely allows the wand to drawselection outlines that appear to encompass colors on many layers

What good is this? Well, suppose you want to apply an effect to both Europe andNorth America With the help of Use All Layers, you can draw a selection outlinethat encompasses both continents After you apply the effect to Europe, you canswitch to the North America layer — the selection outline remains intact — and thenreapply the effect

Ways to Change Selection Outlines

If you don’t draw a selection outline correctly the first time, you have two options.You can either draw it again from scratch, which is a real bore, or you can changeyour botched selection outline, which is likely to be the more efficient solution

Note

You can deselect a selection, add to a selection, subtract from a selection, and even

select the stuff that’s not selected and deselect the stuff that is (If this sounds like a

load of nonsense, keep reading.)

Quick changes

Some methods of adjusting a selection outline are automatic: You choose a

com-mand and you’re finished The following list explains how a few comcom-mands — all

members of the Select menu — work:

✦ Deselect (Ctrl+D): You can deselect the selected portion of an image in three

ways You can select a different portion of the image; click anywhere in the

image window with the rectangular marquee tool, the elliptical marquee tool,

or the lasso tool; or choose Select ➪ Deselect Remember, though, when no

part of an image is selected, the entire image is susceptible to your changes If

you apply a filter, choose a color-correction command, or use a paint tool, you

affect every pixel of the foreground image

✦ Reselect (Ctrl+Shift+D): If you accidentally deselect an image, you can retrieve

the most recent selection outline by choosing Select ➪ Reselect It’s a great

func-tion that operates entirely independently of the Undo command and History

palette, and it works even after performing a long string of selection-unrelated

operations (You can restore older selections from the History palette, but that

usually means undoing operations along the way.)

✦ Inverse (Ctrl+Shift+I): Choose Select ➪ Inverse to reverse the selection.

Photoshop deselects the portion of the image that was previously selected

and selects the portion of the image that was not selected This way, you can

begin a selection by outlining the portion of the image you want to protect,

rather than the portion you want to affect

You can also access the Inverse and Deselect commands from a context-sensitive

pop-up menu in the image window Right-click to make the menu appear

under-neath your cursor

Manually adding and subtracting

Ready for some riddles? When editing a portrait, how do you select both eyes

with-out affecting any other portion of the face? Answer: By drawing one selection and

then tacking on a second selection How do you select a doughnut and leave the

hole behind? Answer: Encircle the doughnut with the elliptical marquee tool, and

then use the same tool to subtract the center

Tip

Photoshop enables you to whittle away at a selection, add pieces on again, whittleaway some more, ad infinitum, until you get it exactly right Short of sheer laziness

or frustration, no reason exists why you can’t eventually create the selection line of your dreams:

out-✦ Adding to a selection outline: To increase the area enclosed in an existing

selection outline, Shift-drag with one of the marquee or lasso tools You alsocan Shift-click with the magic wand tool or Shift-click with one of the marqueetools when the Fixed Size option is active (as described in the “Geometricselection outlines” section earlier in this chapter)

✦ Subtracting from a selection outline: To take a bite from an existing selection

outline, press Alt while using one of the selection tools

✦ Intersecting one selection outline with another: Another way to subtract

from an existing selection outline is to Shift+Alt-drag around the selection with the rectangular marquee, elliptical marquee, or lasso tool You also can Shift+Alt-click with the magic wand tool Shift+Alt-dragging instructsPhotoshop to retain only the portion of an existing selection that also fallsinside the new selection outline I frequently use this technique to confine aselection within a rectangular or elliptical border

If the key-press techniques seem bothersome, use the selection state buttons at theleft end of the Options bar to set your selection tool to add, subtract, or intersectmode (Figure 8-8 labels the icons.) After clicking a button, simply drag to alter theselection outline To toggle the tool back to normal operating mode, click the firstbutton in the bunch Note that the keyboard techniques described in the precedinglist work no matter what button you select in the Options bar For example, if youclick the Intersect icon, Alt-dragging still subtracts from the selection outline

Figure 8-8: You can use the selection state buttons as well as the

Shift and Alt keys when modifying a selection outline

When you’re working with the magic wand, you can right-click to display a sensitive menu that contains the add, subtract, and intersect mode options Clickthe mode you want to use

context-Tip

Normal Add Subtract Intersect

6

Photoshop 6

Photoshop displays special cursors to help you keep track of a tool’s selection

state Suppose that you select part of an image and the lasso tool is active When

you press Shift or click the Add button on the Options bar, Photoshop appends a

little plus sign to the lasso cursor to show you’re about to add A minus sign

indi-cates that you’re set to subtract from the selection outline; a multiply sign appears

when you work in intersect mode If you’re pressing keys to switch tool modes,

Photoshop temporarily selects the corresponding selection state button on the

Options bar as well

Using Shift and Alt like a pro

The roles of the Shift and Alt keys in adding, subtracting, and intersecting selection

outlines can interfere with your ability to take advantage of other functions of the

selection tools For example, when no portion of an image is selected, you can

Shift-drag with the rectangular marquee tool to draw a square But after a selection is

active, Shift-dragging adds a rectangle — not a square — to the selection outline

This is one reason why Adobe added the selection state buttons to the Options bar

After you click a button, the tool adds, subtracts, or intersects, with no additional key

presses on your part, depending on which button you click But if you want to hide

the Options bar or you just prefer pressing keys to clicking buttons, you can control

the selection tools from the keyboard without giving up any selection flexibility

The trick is to learn when to press Shift and Alt Sometimes you have to press the

key before you begin your drag; other times you must press the key after you begin

the drag but before you release For example, to add a square to a selection outline,

Shift-drag, release Shift while keeping the mouse button pressed, and press Shift

again to snap the rectangle to a square The same goes for adding a circle with the

elliptical marquee tool

The following list introduces you to a few other techniques They sound pretty

elaborate, I admit, but with a little practice, they become second nature (so does

tightrope walking, but don’t let that worry you) Before you try any of them, be sure

to select Normal from the Style pop-up menu on the Options bar

✦ To subtract a square or a circle from a selection, Alt-drag, release Alt, press Shift,

drag until you get it right, release the mouse button, and then release Shift

✦ To add a rectangle or an ellipse by drawing from the center outward,

Shift-drag, release Shift, press Alt, and hold Alt until after you release the mousebutton You can even press the spacebar during the drag to move the mar-quee around, if you like

✦ To subtract a marquee drawn from the center outward, Alt-drag, release Alt,

press Alt again, and hold the key down until after you release

✦ What about drawing a straight-sided selection with the lasso tool? To add a

straight-sided area to an existing selection, Shift-drag with the tool for a shortdistance With the mouse button still down, release Shift and press Alt Thenclick around as you normally would, while keeping the Alt key down

6

Photoshop 6

Tip

✦ To subtract a straight-sided area, Alt-drag with the lasso, release Alt, press Altagain, and click around with the tool.

If you can’t manage the last two lasso-tool techniques, switch to the polygonal lassoinstead In fact, the reason Adobe provided the polygonal lasso tool was to accom-modate folks who don’t want to deal with pressing Alt seven times during a singledrag (which I strangely quite enjoy)

Adding and subtracting by command

Photoshop provides several commands under the Select menu that automaticallyincrease or decrease the number of selected pixels in an image according to numer-ical specifications The commands in the Select ➪ Modify submenu work as follows:

✦ Border: This command selects an area of a specified thickness around the

perimeter of the current selection outline and deselects the rest of the tion For example, to select a 6-point-thick border around the current selec-tion, choose Select ➪ Modify ➪ Border, enter 6 in the Width option box, andpress Enter But what’s the point? After all, if you want to create an outlinearound a selection, you can accomplish this in fewer steps by choosing Edit ➪Stroke The Border command, however, broadens your range of options Youcan apply a special effect to the border, move the border to a new location, oreven create a double-outline effect by first applying Select ➪ Modify ➪ Borderand then applying Edit ➪ Stroke

selec-✦ Smooth: This command rounds off the sharp corners and weird anomalies in

the outline of a selection When you choose Select ➪ Modify ➪ Smooth, theprogram asks you to enter a Sample Radius value Photoshop smoothes outcorners by drawing little circles around them; the Sample Radius value deter-mines the radius of these circles Larger values result in smoother corners.The Smooth command is especially useful in combination with the magicwand After you draw one of those weird, scraggly selection outlines with thewand tool, use Select ➪ Modify ➪ Smooth to smooth out the rough edges

✦ Expand and Contract: Both of these commands do exactly what they say,

either expanding or contracting the selected area by a specified amount Forexample, if you want an elliptical selection to grow by 8 pixels, chooseSelect ➪ Modify ➪ Expand, enter 8, and call it a day These are extremely usefulcommands; I refer to them several times throughout the book

Photoshop 6 enables you to expand and contract selections by as many as

100 pixels, up from the previous limit of 16 The upper limits of the Border andSmooth commands were raised also (to 200 and 100 pixels, respectively), but

my guess is that you’ll have less reason to take advantage of those changesthan you will the new ranges for Expand and Contract

6

Photoshop 6

Tip

Both Expand and Contract have a flattening effect on a selection To roundthings off, apply the Smooth command with a Sample Radius value equal tothe number you just entered into the Expand Selection or Contract Selectiondialog box You end up with a pretty vague selection outline, but what do youexpect from automated commands?

In addition to the Expand command, Photoshop provides two other commands —

Grow and Similar — that increase the area covered by a selection outline Both

com-mands resemble the magic wand tool because they measure the range of eligible

pix-els by way of a Tolerance value In fact, the commands rely on the same Tolerance

value (on the Options bar) that you set for the magic wand So if you want to adjust

the impact of either command, you must first select the magic wand and then apply

the commands:

✦ Grow: Choose Select ➪ Grow to select all pixels that both neighbor an existing

selection and resemble the colors included in the selection, in accordancewith the Tolerance value In other words, Select ➪ Grow is the commandequivalent of the magic wand tool If you feel constrained because you canonly click one pixel at a time with the magic wand tool, you may prefer toselect a small group of representative pixels with a marquee tool and thenchoose Select ➪ Grow to initiate the wand’s magic

✦ Similar: Another member of the Select menu, Similar works like Grow, except

the pixels needn’t be adjacent When you choose Select ➪ Similar, Photoshopselects any pixel that falls within the tolerance range, regardless of the loca-tion of the pixel in the foreground image

Although both Grow and Similar respect the magic wand’s Tolerance value, they

pay no attention to the other wand options — Contiguous, Use All Layers, and

Anti-aliased Grow always selects contiguous regions only; Similar selects

noncontigu-ous areas Neither can see beyond the active layer or produce antialiased selection

outlines

One of the best applications for the Similar command is to isolate a complicated

image set against a consistent background whose colors are significantly lighter or

darker than the image Consider Figure 8-9, which features a dark and ridiculously

complex foreground image set against a continuous background of medium-to-light

brightness values The following steps explain how to separate this image using the

Similar command in combination with a few other techniques I’ve described thus far

STEPS: Isolating a Complex Image Set Against a

Plain Background

1 Use the rectangular marquee tool to select some representative portions of

the background In Figure 8-9, I selected the lightest and darkest portions of

the background along with some representative shades in between Remember,you make multiple selections by Shift-dragging with the tool

Note

Tip

Figure 8-9: Before choosing Select ➪ Similar, select a few sample portions

of the background for Photoshop to base its selection range

2 Double-click the magic wand tool icon to display the Tolerance option box

on the Options bar For my image, I entered a Tolerance value of 16, a

rela-tively low value, in keeping with the consistency of the background If yourbackground is less homogenous, you may want to enter a higher value Makecertain you turn on the Anti-aliased check box

3 Choose Select ➪ Similar Photoshop should select the entire background If

Photoshop fails to select all the background, choose Edit ➪ Undo (Ctrl+Z) anduse the rectangular marquee tool to select more portions of the background.You may also want to increase the magic wand’s Tolerance value If Photoshop’sselection bleeds into the foreground image, try reducing the Tolerance value

4 Choose Select ➪ Inverse Or press Ctrl+Shift+I Photoshop selects the

fore-ground image and deselects the backfore-ground

5 Modify the selection as desired If the detail you want to select represents

only a fraction of the entire image, Shift+Alt-drag around the portion of theimage you want to retain using the lasso tool In Figure 8-10, I Shift+Alt-dragged with the polygonal lasso tool to draw a straight-sided outline around the selection

6 Congratulations, you’ve isolated your complex image Now you can filter

your image, colorize it, or perform whatever operation inspired you to selectthis image in the first place I wanted to superimpose the image onto a differ-ent background, so I copied the image to the Clipboard (Ctrl+C), opened thedesired background image, and then pasted the first image into place (Ctrl+V).The result, shown in Figure 8-11, still needs some touching up with the paintand edit tools, but it’s not half bad for an automated selection process

Figure 8-10: Shift+Alt-drag with the polygonal lasso tool to intersect the area

you want to select with a straight-sided outline

Figure 8-11: The completed selection superimposed onto a new background.

Whenever you introduce a selection into another image — by copying and pasting or

by dragging the selection and dropping it into another image window — Photoshopautomatically assigns the selection to a new layer This is a great safety mechanismbecause it prevents you from permanently affixing the selection to its new back-ground But it also limits your file format options when saving an image; you can’tsave in a format other than the native Photoshop format, PDF, or TIFF (the last twonow offer layer support) without first flattening the image For the big story on lay-ers, read Chapter 12

Softening selection outlines

You can soften a selection in two ways The first method is antialiasing, introduced inChapter 5 Antialiasing is an intelligent and automatic softening algorithm that mimicsthe appearance of edges you’d expect to see in a sharply focused photograph

Where did the term antialias originate? Anytime you try to fit the digital equivalent

of a square peg into a round hole — say, by printing a high-resolution image to alow-resolution printer — the data gets revised during the process This revised data,

called an alias, is frequently inaccurate and undesirable Antialiasing is the act of

revising the data ahead of time, essentially rounding off the square peg so it looksnice as it goes into the hole According to a reader who spent time at MIT’sArchitecture Machine Group, “We did the first work with displaying smooth lines

We called the harsh transitions jaggies and the display process dejaggying.

Somehow, this easy-to-understand term slid sideways into ‘alias’ (which it isn’t,really, but it’s too late to change).” Now you know

When you draw an antialiased selection outline in Photoshop, the program lates the hard-edged selection at twice its actual size The program then shrinks theselection in half using bicubic interpolation (described in Chapter 2) The result is acrisp image with no visible jagged edges

calcu-The second softening method, feathering, is more dramatic Feathering graduallydissipates the selection outline, giving it a blurry edge Photoshop accommodatespartially selected pixels; feathering fades the selection both inward and outwardfrom the original edge

You can specify the number of pixels affected either before or after drawing a tion To feather a selection before you draw it with a marquee or lasso tool, enter

selec-a vselec-alue in the Feselec-ather option box, found on the Options bselec-ar in Photoshop 6 Tofeather a selection after drawing it, choose Select ➪ Feather or press Ctrl+Alt+D.You also can right-click in the image window and then choose Feather from the pop-up menu that appears next to your cursor

The Feather Radius value determines the approximate distance over which Photoshopfades a selection, measured in pixels in both directions from the original selection out-line Figure 8-12 shows three selections lifted from the image at the bottom of the figure

Note

Note

The first selection is antialiased only I feathered the second and third selections,

assigning Feather Radius values of 4 and 12, respectively As you can see, a small

feather radius makes a selection appear fuzzy; a larger radius makes it fade into view

Figure 8-12: Three clones selected with the elliptical marquee

tool The top image is antialiased and not feathered, the next

is feathered with a radius of 4 pixels, and the third is feathered

with a radius of 12 pixels

The math behind the feather

A few eagle-eyed readers have written to ask me why feathering blurs a selectionoutline more than the number of pixels stated in the Feather Radius value A radius

of 4 pixels actually affects a total of 20 pixels: 10 inward and 10 outward The reason

revolves around Photoshop’s use of a mathematical routine called the Gaussian bell

curve, which exaggerates the distance over which the selection outline is blurred.

Figure 8-13 demonstrates the math visually The top-left image shows a hard-edgedelliptical selection filled with white against a black background To its right is a sideview of the ellipse, in which black pixels are short and white pixels are tall (Okay,

so it’s really a graph, but I didn’t want to scare you.) Because no gray pixels are inthe ellipse, the side view has sharp vertical walls

The bottom-left image shows what happens if I first feather the selection with aradius of 4 pixels and then fill it with white The side view now graphs a range ofgray values, which taper gradually from black to white See those gray areas on the

sides (each labeled Diameter)? Those are the pixels that fall into the 8-pixel

diame-ter, measured 4 pixels in and out from the original selection outline These grayareas slope in straight lines

Figure 8-13: Here are some graphic demonstrations of what happens when

you feather a selection Photoshop tapers the ends of the feathered selections (shown by the black areas, bottom right) to prevent your eye from easily detecting where the feathering starts and stops

The rounded areas of the side view — painted black — are the Gaussian bell curves.

These are appended to the radius of the feather to ensure smooth transitions between

the blurry edges and the selected and deselected pixels Programs that do not include

these extra Gaussian curves end up producing ugly feathered selections that appear

to have sharp, incongruous edges

If exact space is an issue, you can count on the Feather command affecting about 2.7

times as many pixels as you enter into the Feather Radius option box, both in and

out from the selection That’s a total of 5.4 times as many pixels as the radius in all

If this was more than you wanted to know, cast it from your mind Feathering makes

the edges of a selection fuzzy — ’nuff said

Putting feathering to use

You can use feathering to remove an element from an image while leaving the

back-ground intact, a process described in the following steps The image described in

these steps, shown in Figure 8-14, is a NASA photo of a satellite with the Earth in the

background I wanted to use this background with another image, but to do so I first

had to eliminate that satellite By feathering and cloning a selection outline, I

cov-ered the satellite with a patch so seamless you’d swear the satellite was never there

STEPS: Removing an Element from an Image

1 Draw a selection around the element using the lasso tool The selection

needn’t be an exact fit; in fact, you want it rather loose, so allow a buffer zone

of at least 6 pixels between the edges of the image and the selection outline

Figure 8-14: Your mission, if you choose to accept it, is to remove the

satellite by covering it with selections cloned from the background

Tip

2 Drag the selection outline over a patch in the image Now that you’ve specified

the element you want to remove, you must find a patch, that is, some portion ofthe image to cover the element in a manner that matches the surrounding back-ground In Figure 8-15, the best match seemed an area just below and to the right

of the satellite To select this area, move the selection outline independently ofthe image merely by dragging it with the lasso tool (Dragging a selection with aselection tool moves the outline without affecting the pixels.) Make certain youallow some space between the selection outline and the element you’re trying

to cover

Figure 8-15: After drawing a loose outline around the satellite with the

lasso tool, I dragged the outline to select a portion of the background

3 Choose Select ➪ Feather Or press Ctrl+Alt+D Enter a small value (8 or less)

in the Feather Radius option box — just enough to make the edges fuzzy (I entered 3.) Then press Enter to initiate the operation

4 Clone the patch onto the area you want to cover Select the move tool by

pressing V Then Alt-drag the feathered selection to clone the patch and tion it over the element you want to cover, as shown in Figure 8-16 To alignthe patch correctly, choose Select ➪ Hide Extras (Ctrl+H) to hide the marchingants and then nudge the patch into position with the arrow keys

posi-5 Repeat as desired My patch was only partially successful The upper-left

cor-ner of the selection matches clouds in the background, but the lower-rightcorner is dark and cloudless, an obvious rift in the visual continuity of theimage The solution: Try again With the lasso tool, I drew a loose outlinearound the dark portion of the image and dragged it up and to the left asshown in Figure 8-17

Figure 8-16: Next, I used the move tool to Alt-drag the feathered

selection over the satellite Sadly, the patch was imperfect and

required further adjustments

Figure 8-17: I used the lasso tool to draw a new outline around the

dark, cloudless portion of the patch Then I dragged the outline to

a different spot in the background