2. Display models

The various image-handling modules differ as to how/where images will be displayed on a website.

Site-controlled vs inline display

On most sites, the designer pre-determines the size of images and their placement via Views and/or theming, pre-determining specific locations for images in the display page or within the node layout. Many site designers/administrators prefer to let users just upload their pictures without having to consider how they will be formatted, and some don't want to allow even technically proficient content authors control over the content's appearance.

I will use the term site-controlled display in discussing these types of image handling methods. Any module that enables the display of images using custom fields and content types (via CCK module) is an example of this category, and Views is another such display method that is often (but not exclusively) used in conjunction with CCK fields.

On the other hand, some sites may want to make things easy for less technical users, but are willing to allow more technical authors (or those, like an in-house team, available for training) some flexibility in formatting images. In-line display is a method that lets the creator of a node determine the size and place of images, inserting them wherever they choose within the body text of their posting. Here, the site designer isn't in complete control of the site pages' appearance, and it is possible that a user would for example insert graphics that are so large it causes problems for the site's layout when displaying a given node.

Image Assist and Inline modules are examples of this method, allowing content authors to embed "macro tags" to replicate the functionality of traditional HTML <img> syntax in line with their body text.

Asset module is the only one I know of that enables both CCK fields and in-line macro tag methods.

Displaying only links to files

Obviously this is not really "displaying" an image, but some modules offer this ability as an alternative or a fallback method when an image is too large.

Preset derivatives

A better method of handling large images is to present a smaller version when appropriate. Several modules will automatically generate thumbnails, or even a whole series of different versions of an image file. These alternative versions are knows as "preset derivatives", and Imagecache module currently has the most sophisticated and flexible feature set in this arena.