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Automatically Resizing Image Fields with ImageCache

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ImageCache provides automated image manipulation in conjunction with the image CCK field. To use it, you need to download, install, and enable the modules in ImageAPI and ImageCache, as shown in Tables 7.2 and 7.3.

ImageCache consists of a variety of presets, which are actions that are invoked as needed for image fields. When you go to Administer, Site Building, ImageCache (admin/build/imagecache), you see the list of your presets and can add new ones, as shown in Figure 7.14.

TABLE 7.2 ImageCache Module Reference

Download from Enable in section Permissions

ImageCache ImageCache ImageCache ImageCache

Administration

Administer, Site Building, ImageCache (admin/build/lmagecache)

project/imagecache ImageCache

Administer Imagecache

Flush Imagecache

View Imagecache basic

View Imagecache thumbnail

List, Add Preset

TABLE 7.3 ImageAPI Module Reference

Download from project/imageapi (moving to core in Drupal 7)

Enable in section ImageCache

Permissions none

Administration none

To the right of each preset are links that enable you to edit and delete them, as well as to export them for further use. The Flush link is an example of the benefits you get from using ImageCache. Drupal can cache the preset results for each preset that has been applied to an image. The Flush command will remove all those cached images; there will be a performance hit the first time they need to be recreated for any given image, but you may need to do this if you change the settings.

FIGURE 7.14

List and view ImageCache presets.

In Figure 7.15, you can see the actions that you can add to a preset. (You can add several to an individual preset.)

When you click an action to add it, you fill in the necessary values for that action, as shown in Figure 7.16.

The actions and transformations that you can choose are standard image manipulation ones. Most of the actions provide a check box that lets you specify whether the image can be upscaled—that is, if it can be made larger than the original. This can result in poor image quality. In general, it is better to downscale images, making them smaller than the original. (That is why multimegapixel cameras take photos that are more easily manipulated than low-resolution cameras.) The other action to watch out for is an action that changes an image's aspect ratio. Such actions cause distortions in the image. Each action has a brief description that provides information about its consequences. Also, the fact that this is not Drupal terminology, but image manipulation terminology, makes it easier for you to get more information if you want to study a book or article for further information.