The features and syntax of image catalogs are described in this section.
Image catalogs offer the following features:
- Allow persistent association of images with certain metadata and modifier commands.Entries in image catalogs are referenced using a shortcut notation * rootId/objId * , where * rootId * identifies the image catalog and * objId * identifies a data record in the catalog.
- Provide defaults for certain request attributes, such as the JPEG quality or whether a watermark is to be applied.
- Manage fonts, ICC profiles, macro definitions, and request templates
Even if no specific image catalogs are defined, all features of image catalogs are available via the default catalog ( default.ini).
If * rootId * in the request's URL path matches attribute::RootId of a specific image catalog, that catalog will become the main catalog for this request. The main catalog provides the default attributes and settings for the entire request. If no match is found, the default catalog is used instead.
A catalog identified in a src= or mask= command provides the following catalog attributes and data to the current layer:
the default extension for all image file paths in the current layer
default for catalog::Expiration or expiration of the current layer if no catalog record is involved
the working ICC color profile, render intent, and blackpoint compensation flag for the request and/or the current layer
used for all source file paths of the current layer
default for catalog::Resolution only
default for the anchor= value of the current layer
the smallest expiration value of all layers is used as the time-to-live value of the reply image
the source image color profile for the current layer
the image map data for the current layer
default for mask= for the current layer
prefix commands for the current layer (each command in catalog::Modifier can be overridden by the same command in the URL, if specified for the same layer)
the source image file for the current layer
postfix commands for the current layer (similar to catalog::Modifier , but commands in catalog::PostModifier override the same commands specified in the URL or in catalog::Modifier )
the object resolution of the current layer
Within the same layer, src= and mask= must reference the same image catalog (if any).
A catalog identified in an icc= command is used only to look up an entry from the catalog's ICC profile table. No other catalog attributes or data are involved.
If, * rootId * resolves to a catalog, and * objId * is matched with a catalog::Id in this catalog, then * rootId/objId * is effectively replaced by the catalog entry somewhat like this:
src=attribute::RootPath/catalog::Path& mask=attribute::RootPath/catalog::MaskPath& anchor=catalog::Anchor& catalog::Modifier& catalog::PostModifier