Linked slices in GIF and PNG-8 format share a color palette and dither pattern. The dither pattern is applied across adjacent slice boundaries to prevent the appearance of seams between the slices. (See “Optimization options for GIF and PNG-8 formats” on page 420.)

Note: You can also link slices in the Photoshop Save for Web dialog box. (See “Working with slices in the Save for Web dialog box (Photoshop)” on page 417.)

To link slices:

1 Select two or more slices you want to link.

Note: If the first slice you select is a user slice, any auto slices you link to the first slice become user-slices. If the first slice you select is an auto slice, any user slices you select are linked to the auto slice group.

2 Choose Slices > Link Slices.

Each linked set of user slices is assigned a different color for the slice display graphics in the upper left corner of the slice. This helps to identify all the slices in one set.

To unlink user slices:

Do one of the following:

•To unlink a user slice, select the slice, and then choose Slices > Unlink Slices.

•To unlink all user slices in a set, select a slice in the set, and choose Slices > Unlink Set.

•To unlink all user slices in an image, choose Slices > Unlink All.

Creating and viewing image maps (ImageReady)

Image maps enable you to link an area of an image to a URL. You can set up multiple linked areas—called image map areas—in an image, with links to text files; other images; audio, video, or multimedia files; other pages in the Web site; or other Web sites. You can also create rollover effects in image map areas.

The main difference between using image maps and using slices to create links is in how the source image is exported as a Web page. Using image maps keeps the exported image intact as a single file, while using slices causes the image to be exported as a separate file. Another difference between image maps and slices is that image maps enable you to link circular, polygonal, or rectangular areas in an image, while slices enable you to link only rectangular areas. If you need to link only rectangular areas, using slices may be preferable to using an image map.

Note: To avoid unexpected results, do not create image map areas in slices that contain URL links—either the image map links or the slice links may be ignored in some browsers.

Creating image maps

You can create image map areas using an image map tool or a layer.

Tool-based image map areas Are created using an image map tool—you drag in the image to define the image map area. You can view and set options for tool-based image maps in the Image Map palette.

Layer-based image map areas Are created from a layer—the layer’s content defines the shape of the image map area and the image map inherits the name of the layer. If you edit the layer’s content, the image map area automatically adjusts to encompass the new pixels. You can view and set options for layer-based image map areas in the Image Map palette.

If you plan to add a rollover effect to an image map area, it is often preferable to use a layer-based image map area rather than a tool-based image map area. For example, if you create a rollover button that displays a glow effect in the Over state, a layer-based image map area will automatically adjust to encompass the pixels that are produced by the glow.

Important: If you overlap image map areas, the topmost area is active.

Layer-based rectangle image map compared to polygonal image map

To create an image map area using an image map tool:

1Select the rectangle image map tool , the circle image map tool , or the polygon image map tool in the toolbox.

2For the rectangle or circle image map tool, select Fixed Size to specify set values for the image map area’s dimensions. Enter pixel values in whole numbers.

3Do one of the following to define the image map area:

•With the rectangle or circle image map tool, drag over the area you want to define. Shift-drag to constrain the area to a square. Alt-drag (Windows) or Option-drag (Mac OS) to drag an image map area from its center.

•With the polygon image map tool, click in the image to set the starting point. Position the pointer where you want the first straight segment to end, and click. Continue clicking to set endpoints for subsequent segments. Hold down Shift to constrain the segment to 45° increments. To close the border, double-click, or position the pointer over the starting point (a closed circle appears next to the pointer) and click.

To add points to a polygon image map area, select the image map select tool, and Shift-click where you want to add a point. To remove points from a polygon image

map area, select the image map select tool, and Alt-click (Windows) or Optionclick (Mac OS) the points you want to remove.

To create an image map area from a layer:

1In the Layers palette, choose a layer from which to create an image map area. (To use multiple layers in one image map area, first merge the layers.)

2Choose Layer > New Layer Based Image Map Area.

Converting layer-based image maps to tool-based image maps

Because a layer-based image map area is tied to the pixel content of a layer, the only way to move, resize, or align it is to edit the layer. You can convert a layer-based image map area to a tool-based image map area to unlink it from the layer.

To convert a layer-based image map area to a tool-based image map area:

1Select a layer-based image map area using the image map select tool . (See “Selecting image maps” on page 386.)

2Choose Promote Layer Based Image Map Area from the Image Map palette menu. If the layer contains multiple, non-overlapping areas of pixel content, multiple tool-based image map areas are produced.

Viewing image maps

When you select the image map select tool, image map areas show automatically.You can also show or hide image map areas using the Image Map Visibility button.

Image map preferences determine how image map areas appear in the document window. You can set preferences for image map lines, line color, and color adjustments.

To show or hide image map areas:

Do one of the following:

•Click the Image Map Visibility button in the toolbox.

•Choose View > Show > Image Maps.

•Choose View > Show Extras. This command also shows or hides selection edges, slices, text bounds, text baseline, and text selections. (See “Working with Extras” on page 47.)

To set image map display preferences:

1 Do one of the following:

•In Windows and Mac OS 9.x, choose Edit > Preferences > Image Maps.

•In Mac OS X, choose ImageReady > Preferences > Image Maps.

2To change the color of image map lines, choose a color from the Line Color pop-up menu. Changing the color of image map lines also changes the line color of selected image map areas to a contrasting color.

3To change the strength of image map color adjustments, enter a value, or choose a value from the Image Map Overlay pop-up slider.The value determines the extent of color adjustments that dim the brightness and contrast of unselected image map areas.

4To display image map lines only and deselect color adjustment display, select Show Lines Only.

5To show a bounding box for circular image map areas, select Show Bounding Box.