Optimization options for JPEG format

You can use masks from type layers, shape layers, and alpha channels to vary the quality level across an image. This technique produces higher-quality results in critical image areas without sacrificing file size. (See “Using weighted optimization” on page 428.)

Optimized Select Optimized to create an enhanced JPEG with a slightly smaller file size. The Optimized JPEG format is recommended for maximum file compression; however, some older browsers do not support this feature.

Progressive Select Progressive to create an image that displays progressively in a Web browser. The image will display as a series of overlays, enabling viewers to see a lowresolution version of the image before it downloads completely.

Note: Progressive JPEGs require more RAM for viewing, and are not supported by some browsers.

Blur Specify the amount of blur to apply to the image. This option applies an effect identical to that of the Gaussian Blur filter and allows the file to be compressed more, resulting in a smaller file size. A setting of 0.1 to 0.5 is recommended.

ICC Profile Select ICC Profile to preserve the ICC profile of the artwork with the file. ICC profiles are used by some browsers for color correction. (See “Setting up color management” on page 104.)

Matte Specify a fill color for pixels that were transparent in the original image:

•Click the Matte color swatch and select a color in the color picker.

•Choose an option from the Matte menu.

Pixels that were fully transparent in the original image are filled with the selected color, pixels that were partially transparent in the original image are blended with the selected color.

Preserve EXIF Metadata (ImageReady) Select to preserve metadata from a digital camera.

Optimization options for PNG-24 format

PNG-24 is suitable for compressing continuous-tone images; however, it produces much larger files than JPEG format. (See “About file formats” on page 453.)

The advantage of using PNG-24 is that it can preserve up to 256 levels of transparency in an image. To save an image with multilevel transparency, select Transparency. For more information on the Interlaced,Transparency, and Matte options, see “Optimization options for GIF and PNG-8 formats” on page 420.

Optimization options for WBMP format

WBMP format is the standard format for optimizing images for mobile devices, such as cell phones. WBMP supports 1-bit color, which means that WBMP images contain only black and white pixels.

Choose an option from the Dither Algorithm menu to determine the method for converting pixel values to black or white:

•No Dither applies no dither to the image.

•Diffusion applies a random pattern that is usually less noticeable than Pattern dither. The dither effects are diffused across adjacent pixels. If you select this algorithm, specify a Dither percentage to control the amount of dithering that is applied to the image.You can use masks from type layers, shape layers, and alpha channels to vary the Dither

percentage across an image. This technique produces higher-quality results in critical image areas without sacrificing file size. (See “Using weighted optimization” on

page 428.)

Note: Diffusion dither may cause detectable seams to appear across slice boundaries. Linking slices diffuses the dither pattern across all linked slices, and eliminates the seams.

•Pattern applies a halftone-like square pattern to determine the value of pixels.

•Noise applies a random pattern similar to the Diffusion dithering, but without diffusing the pattern across adjacent pixels. No seams appear with the Noise algorithm.

Saving and resetting optimization settings

You can save optimization settings as a named set and apply the settings to other images. Settings that you save appear in the Settings pop-up menu, together with the predefined named settings. If you edit a named set or a predefined set, the Settings menu displays the term “Unnamed.”

In Photoshop, after you optimize an image, you can return to the artboard without losing your settings. When you choose the Save for Web command again, the optimization settings are just as you left them.

To save a named set of optimization settings:

1Set optimization options as desired, and choose Save Settings from the Optimize pop-up menu (Photoshop) or the Optimize palette menu (ImageReady).

2Name the settings, and save them in the Presets/Optimized Settings folder inside the Photoshop program folder.

Note: If you save the settings in a location other than the Presets/Optimized Settings folder, they will not be available from the Settings pop-up menu.

To edit a named set of optimization settings:

1Choose the named set from the Settings pop-up menu.

2Edit the optimization settings as desired. The Settings menu will display the term “Unnamed,” since the settings no longer match a named set.

3Choose Save Settings from the Optimize pop-up menu (Photoshop) or the Optimize palette menu (ImageReady), and save the settings with the name of the original set.

To delete optimization settings:

1Choose a named set or predefined set of optimization settings from the Settings pop-up menu.

2Choose Delete Settings from the Settings panel menu.

Note: You cannot restore deleted settings, so use the Delete Settings command with care.

To save the current optimization setting (Photoshop):

Do one of the following:

•To save the settings and close the Save for Web dialog box, click Done.

•To save the settings without closing the Save for Web dialog box, press Alt (Windows) or Option (Mac OS), and click Remember.

To reset optimization settings to the last saved version (Photoshop):

Press Alt (Windows) or Option (Mac OS), and click Reset.

Resizing the image during optimization (Photoshop)

When optimizing an image in the Photoshop Save For Web dialog box, you can resize the image to specified pixel dimensions or to a percentage of the original size.

To change the pixel dimensions of an image during optimization:

1Click the Image Size tab in the Save For Web dialog box.

2To maintain the current proportions of pixel width to pixel height, select Constrain Proportions.

3Enter values for Width, Height, or Percent.

4Choose an interpolation method from the Quality pop-up menu:

•Jagged (Nearest Neighbor) for the faster, but less precise, method. This method is recommended for use with illustrations containing non-anti-aliased edges, to preserve hard edges and produce a smaller file.

•Smooth (Bicubic) for the slower, but more precise, method, resulting in smoother tonal gradations.

For more information on interpolation, see “About resampling” on page 66.

5 Click Apply.

Controlling optimization (ImageReady)

By default, Photoshop and ImageReady automatically regenerate the optimized image when you click the Optimized, 2-Up, or 4-Up tab at the top of the document (if you have modified the image since the last optimization), when you change optimization settings with the optimized image displayed, or when you edit the original image.

In ImageReady, you can turn off auto-regeneration so that the last version of the optimized image remains in the image window until you manually reoptimize the image or reactivate auto-regeneration.This feature is useful if you want to edit the image without pausing for reoptimization with each modification.You can also cancel optimization while it’s in progress, and preserve the previous image.

When auto-regeneration is turned off, the Regenerate button appears in the lowerright corner of each optimized image view. A regeneration alert symbol also appears in the Color Table palette if the optimized image is in GIF or PNG-8 format, indicating that the color table is out of date.

To turn Auto Regenerate on or off:

In the Optimize palette, choose Auto Regenerate from the palette menu. A check mark indicates that the option is turned on.