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Using channels to modify dithering, Using channels to modify color reduction

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ADOBE PHOTOSHOP 6.0 329 User Guide Using channels to modify dithering When you use an alpha channel to optimize the amount of dithering in a GIF or PNG-8 image, white areas of the mask yield the most dithering, and black areas of the mask yield the least dithering. You can adjust the maximum and minimum levels of dithering in the Modify Quality Setting dialog box. To use a channel to modify dithering: 1 In the Optimize panel/palette, choose a GIF or PNG-8 setting from the Settings menu, or choose GIF or PNG-8 from the file format menu. 2 Click the channel button ( ) to the right of the Dither text box. 3 In the Modify Quality Setting dialog box, choose the desired channel from the Channel menu. In ImageReady, you can choose Save Selection to create a new alpha channel based on the current selection. 4 To preview the results of the weighted optimization, select the Preview option. 5 Define the dithering range: • To set the highest percentage of dithering, drag the right (white) tab on the slider, enter a value in the Maximum text box, or use the arrows to change the current percentage. • To set the lowest percentage of dithering, drag the left (black) tab on the slider, enter a value in the Minimum text box, or use the arrows to change the current percentage. 6 Click OK. Using channels to modify color reduction When you use an alpha channel to optimize the colors in a GIF or PNG-8 image, the white areas of the mask determine what areas of the image are the most important when calculating the color table. White areas of the channel indicate to the color reduction algorithm which pixels are highly important, whereas black areas of the channel indicate which pixels are less important. To use a channel to modify color reduction: 1 In the Optimize panel/palette, choose a GIF or PNG-8 setting from the Settings menu, or choose GIF or PNG-8 from the file format menu. 2 Choose a color reduction algorithm and specify the maximum number of colors. 3 Click the channel button ( ) to the right of the Color Reduction Algorithm pop-up menu. 4 In the Modify Color Reduction dialog box, choose the desired channel from the Channel menu. In ImageReady, you can choose Save Selection to create a new alpha channel based on the current selection. 5 To preview the results of the weighted optimization, select the Preview option. 6 Click OK.

Section	Page
Table of Contents	3
Getting Started	11
Registration	11
Installing Adobe Photoshop and ImageReady	11
Learning Adobe Photoshop and ImageReady	11
Using Web resources	13
Other learning resources	14
Customer support	15
Adobe Photoshop Basics	19
Using tools and palettes	20
Opening images in Photoshop and ImageReady	22
Streamlining your workflow	24
Making tonal and color adjustments	26
Retouching images	27
Making pixel selections	28
Making edits	30
Using layers	32
Compositing images	34
Painting	36
Drawing shapes	37
Creating type	40
Editing type	41
Designing Web graphics	42
Creating animations (ImageReady)	43
Optimizing Web graphics	44
What’s New in Adobe Photoshop 6.0	49
Superb vector support	50
Enhanced vector output	52
Layer styles	52
Interactive image warping	54
Enhanced slicing capabilities	55
Enhanced support for image maps and rollovers	57
Weighted optimization	58
Improved Web workflow	58
Streamlined interface	59
Enhanced layer management	60
Expanded text features	61
Preset Manager	63
Other new and enhanced features	63
Looking at the Work Area	67
Using the toolbox	67
Using the tool options bar	69
Using palettes	70
Using context menus	74
Viewing images	74
Correcting mistakes	78
Reverting to any state of an image	79
Duplicating images	83
Using rulers, the measure tool, guides, and the grid	84
Working with Extras	87
Displaying status information	88
Displaying file and image information	88
Annotating images (Photoshop)	90
Jumping between applications	92
Previewing an image in a browser	94
Managing libraries with the Preset Manager (Photoshop)	95
Setting preferences	96
Resetting all warning dialogs	97
Monitoring operations	98
Closing files and quitting	98
Getting Images into Photoshop and ImageReady	101
About bitmap images and vector graphics	101
About image size and resolution	102
Changing image size and resolution	105
Scanning images	109
Creating new images	110
Opening and importing images	111
Placing files	114
Managing files with WebDAV	116
Working with Color	119
About color modes and models (Photoshop)	119
Color gamuts (Photoshop)	124
Adjusting the monitor display	124
Channels and bit depth (Photoshop)	126
Converting between color modes (Photoshop)	127
Converting to indexed color (Photoshop)	128
Applying colors	128
Making color and tonal adjustments	128
Producing Consistent Color (Photoshop)	131
Why colors sometimes don’tmatch	131
About color management	131
Do you need color management?	132
Creating a viewing environment for color management	133
Setting up color management	134
Using predefined color management settings	134
Customizing color management settings	136
Specifying working spaces	137
Specifying color management policies	138
Customizing advanced color management settings	140
Saving and loading color management settings	140
Synchronizing color management between applications	141
Soft-proofing colors	141
Changing the color profile of a document	143
Embedding profiles in saved documents	144
Obtaining, installing, and updating color profiles	144
Creating an ICC monitor profile	146
Selecting	149
About selections	149
Making pixel selections	149
Adjusting pixel selections	156
Softening the edges of a selection	157
Moving, copying, and pasting selections and layers	159
Working with snap	162
Saving and loading selections	163
Deleting selections	163
Removing fringe pixels from a selection (Photoshop)	164
Extracting objects from their background (Photoshop)	164
Drawing and Editing	171
About drawing and painting	171
Drawing shapes and paths	171
Using the shape tools	174
Using the pen tools (Photoshop)	176
Drawing overlapping shapes (Photoshop)	181
Using the Paths palette (Photoshop)	181
Editing paths (Photoshop)	182
Managing paths (Photoshop)	189
Converting between paths and selection borders (Photoshop)	190
Adding color to paths (Photoshop)	192
Transforming and retouching	192
Using Channels and Masks	195
About channels	195
Using the Channels palette (Photoshop)	195
Managing channels (Photoshop)	197
Mixing color channels (Photoshop)	200
Adding spot colors (Photoshop)	201
Using channel calculations to blend layers and channels (Photoshop)	204
About masks (Photoshop)	207
Creating temporary masks in Quick Mask mode (Photoshop)	207
Storing masks in alpha channels	209
Using Layers	215
About layers	215
About layer sets	216
Using the Layers palette	216
Creating a layered image	220
Grouping layers into sets	223
Moving and aligning the contents of layers	224
Editing layers	226
Creating clipping groups	228
Specifying layer properties	229
Using the Layer Style dialog box (Photoshop)	230
Setting layer blending options	231
Using layer styles	236
Customizing layer styles	240
Creating and editing contours (Photoshop)	246
Hiding portions of a layer	247
Using adjustment layers or fill layers (Photoshop)	252
Managing layered images	256
Using Type	261
About type	261
Creating type	261
Working with type layers	264
Formatting characters	268
Formatting paragraphs	275
Controlling hyphenation and justification	277
Working with composition	277
Setting options for Chinese, Japanese, and Korean type (Photoshop)	277
Designing Web Pages	281
About designing Web pages with Photoshop and ImageReady	281
Creating and viewing slices	282
Selecting and modifying slices	286
Specifying slice options	291
Creating and viewing image maps (ImageReady)	296
Selecting and modifying image maps (ImageReady)	298
Specifying image map options (ImageReady)	301
Selecting an image map type (ImageReady)	302
Working with rollovers (ImageReady)	302
Creating Web photo galleries (Photoshop)	307
Creating Animations (ImageReady)	311
About animation	311
Creating animations	311
Working with layers in animations	316
Viewing animations	319
Optimizing animations	319
Viewing animated images in Photoshop	320
Saving animations	320
Opening and importing files as animations	321
Optimizing Images for theWeb	325
About optimization	325
Viewing images during optimization	326
Choosing a file format for optimization	327
Optimizing images	330
Using weighted optimization	337
Optimizing colors in GIF and PNG-8 images	340
Working with hexadecimal values for color	347
Making transparent and matted images	349
Previewing and controlling dithering	351
Setting optimization preferences (ImageReady)	355
Using a droplet to automate optimization settings (ImageReady)	356
Saving optimized images	357
Setting output options	358
Creating background images	362
Saving and Exporting Images	367
Saving images	367
About file formats	374
Adding file information (Photoshop)	376
Adding digital copyright information	376
Setting preferences for saving files (Photoshop)	376
Creating multiple-image layouts (Photoshop)	377
Placing Photoshop images in other applications (Photoshop)	379
Printing (Photoshop)	385
About printing	385
Printing images	386
Positioning and scaling images	387
Setting output options	388
Selecting halftone screen attributes	389
Printing part of an image	392
Choosing a print encoding method	392
Printing vector graphics	392
Using color management when printing	392
Printing with Adobe PressReady	393
Creating color traps	394
Printing duotones	394
Printing color separations	399
Automating Tasks	403
About actions	403
Using the Actions palette	404
Recording actions	404
Playing actions	409
Setting playback options (Photoshop)	410
Editing actions	410
Managing actions in the Actions palette	412
Using the Batch command (Photoshop)	415
Using droplets	416
Using the Automate commands (Photoshop)	420
External automation	421
Index	423

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329

ADOBE PHOTOSHOP 6.0

User Guide

Using channels to modify dithering

When you use an alpha channel to optimize the

amount of dithering in a GIF or PNG-8 image,

white areas of the mask yield the most dithering,

and black areas of the mask yield the least

dithering. You can adjust the maximum and

minimum levels of dithering in the Modify

Quality Setting dialog box.

To use a channel to modify dithering:

In the Optimize panel/palette, choose a GIF or

PNG-8 setting from the Settings menu, or choose

GIF or PNG-8 from the ﬁle format menu.

Click the channel button (

) to the right of the

Dither text box.

In the Modify Quality Setting dialog box,

choose the desired channel from the Channel

menu. In ImageReady, you can choose Save

Selection to create a new alpha channel based on

the current selection.

To preview the results of the weighted optimi-

zation, select the Preview option.

Deﬁne the dithering range:

•

To set the highest percentage of dithering, drag

the right (white) tab on the slider, enter a value in

the Maximum text box, or use the arrows to

change the current percentage.

•

To set the lowest percentage of dithering, drag

the left (black) tab on the slider, enter a value in the

Minimum text box, or use the arrows to change

the current percentage.

Click OK.

Using channels to modify color reduction

When you use an alpha channel to optimize the

colors in a GIF or PNG-8 image, the white areas of

the mask determine what areas of the image are

the most important when calculating the color

table. White areas of the channel indicate to the

color reduction algorithm which pixels are highly

important, whereas black areas of the channel

indicate which pixels are less important.

To use a channel to modify color reduction: