The DAM API provides the basic mechanism for the abstraction of the storage location of an asset. The API:
- Allows for external storage providers.
- Is used primarily in templating, templates and models. It provides read-only access to assets managed in the Assets app.
Key features of DAM 2.0 API:
- Clean, simple and basic:
- Flexible, extendable and user-friendly. (You can extend the API and create your own asset providers for external systems.)
- Generic, in the sense that it is not coupled to the JCR.
- Capable of connecting to external asset providers and other systems.
- Supporting Industry standard media types
- It is now possible to plug in external asset providers like Flickr, YouTube and file systems.
Architecture
The diagram provides an overview of how the main interfaces and classes of the DAM API relate.
Interfaces
-
Javadoc resource link |
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0 | info.magnolia.dam.api.AssetProviderRegistry |
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className | info.magnolia.dam.api.AssetProviderRegistry |
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renderType | asynchronous |
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is the main entry point. Given an ItemKey
or MediaType
it is responsible for:
- Finding the correct
AssetProvider
. - Finding the correct
AssetRenderer
.
Javadoc resource link |
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0 | info.magnolia.dam.api.AssetProvider |
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className | info.magnolia.dam.api.AssetProvider |
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renderType | asynchronous |
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: Exposes Folder
s and Asset
s from a particular source. Specifics of the storage of these items are left to implementations. While most provider implementations only use the ItemKey.assetId
field of keys passed to the various get
methods, the entire key object is passed for consistency and flexibility. This makes it possible to implement, for example, delegating and aggregating providers.-
Javadoc resource link |
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0 | info.magnolia.dam.api.PathAwareAssetProvider |
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className | info.magnolia.dam.api.PathAwareAssetProvider |
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renderType | asynchronous |
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: Exposes specific operations for AssetProviders
that are aware of paths, for example JCR, CMIS, File system etc. Not all providers need or want to implement these features. The term "path" here should be taken "with a pinch of salt". It could, for example, be a single name or a "relative" path if the provider serves assets from a subset of its underlying data source. -
Javadoc resource link |
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0 | info.magnolia.dam.api.AssetRenderer |
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className | info.magnolia.dam.api.AssetRenderer |
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renderType | asynchronous |
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: Provides AssetRenditions
by bridging an asset's data and some type of converter. AssetRenderers
can be provided by AssetProviders
if the AssetProvider
itself (or the underlying system) is capable of managing the conversion/translation, or via a "global" registry. AssetProviderRegistry.getRendererFor(info.magnolia.dam.api.Asset, com.google.common.net.MediaType)
provides the entry point. It looks up in provider, then in its own registry, and bridges to other possible conversion mechanisms that are independent of Magnolia DAM. -
Javadoc resource link |
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0 | info.magnolia.dam.api.Asset |
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className | info.magnolia.dam.api.Asset |
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renderType | asynchronous |
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: An Asset
is a digital resource with associated metadata. -
Javadoc resource link |
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0 | info.magnolia.dam.api.Folder |
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className | info.magnolia.dam.api.Folder |
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renderType | asynchronous |
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: A Folder
represents a structural item holding Asset
s. Depending on the provider, this can be directly mapped to the concept of folders/directories (JCR, FileSystems etc.), and for other types it may map to the concept of albums, playlists, sets, etc. Javadoc resource link |
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0 | info.magnolia.dam.api.Item |
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className | info.magnolia.dam.api.Item |
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renderType | asynchronous |
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: Defines a common interface for Asset
and Folder
. -
Javadoc resource link |
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0 | info.magnolia.dam.api.AssetQuery |
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className | info.magnolia.dam.api.AssetQuery |
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renderType | asynchronous |
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: Represents a query to an AssetProvider
. Use new AssetQuery.Builder()...build()
to construct instances. Javadoc resource link |
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0 | info.magnolia.dam.api.AssetRendition |
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className | info.magnolia.dam.api.AssetRendition |
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renderType | asynchronous |
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: An AssetRendition
is a "view" on a asset for a specific MediaType
. It can be a simple resize of an image, or a document conversion.
Enum
-
Javadoc resource link |
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0 | info.magnolia.dam.api.AssetProviderCapability |
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className | info.magnolia.dam.api.AssetProviderCapability |
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renderType | asynchronous |
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: Clients can ask a provider if they support a certain feature before attempting to use it. Typically, this would enable/disable certain UI features. In some cases, this will also indicate that client code can cast to a specific interface. (e.g. PathAwareAssetProvider
for hierarchical
). If support for write operations is added, this enum will be extended with new capabilities.
Classes
Javadoc resource link |
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0 | info.magnolia.dam.api.AbstractAssetProvider |
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className | info.magnolia.dam.api.AbstractAssetProvider |
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renderType | asynchronous |
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: Convenient abstract base class for implementations. Enables configuration of MediaType
s that the implemented AssetProvider
provides. -
Javadoc resource link |
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0 | info.magnolia.dam.api.AbstractItem |
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className | info.magnolia.dam.api.AbstractItem |
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renderType | asynchronous |
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: Common superclass for any dam Item
.
Javadoc resource link |
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0 | info.magnolia.dam.api.AssetQuery.Builder |
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className | info.magnolia.dam.api.AssetQuery.Builder |
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renderType | asynchronous |
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: A builder for AssetQuery
that provides a fluent API.
-
Javadoc resource link |
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0 | info.magnolia.dam.api.ItemKey |
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className | info.magnolia.dam.api.ItemKey |
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renderType | asynchronous |
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: A composite key. In the DAM every Asset
and Folder
is identified by its provider's ID and its provider-specific ID (i.e the ID with which the provider can uniquely identify the asset).
Javadoc resource link |
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0 | info.magnolia.dam.api.metadata.AssetMetadata |
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className | info.magnolia.dam.api.metadata.AssetMetadata |
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renderType | asynchronous |
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: A common interface for asset metadata. Different types of metadata can be exposed through Asset
by extending this interface. The AssetProvider
should implement support for those. Specific metadata interfaces should expose methods with explicit names and return types, and ideally provide property descriptions in the Javadocs. Metadata is retrieved through an Asset
by passing the specific type of metadata, i.e, a class object that extends this interface. Javadoc resource link |
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0 | info.magnolia.dam.api.metadata.DublinCore |
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className | info.magnolia.dam.api.metadata.DublinCore |
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renderType | asynchronous |
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: A collection of Dublin Core metadata names. Extends AssetMetadata. Methods: getContributor
,getCoverage
, getCreated
, getCreator
, getDate
, getDescription
, getFormat
, getIdentifier
, getLanguage
, getModified
, getPublisher
, getRelation
, getRights
, getSource
, getSubject
, getTitle
, getType
. Javadoc resource link |
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0 | info.magnolia.dam.api.metadata.MagnoliaAssetMetadata |
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className | info.magnolia.dam.api.metadata.MagnoliaAssetMetadata |
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renderType | asynchronous |
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: Defines Magnolia-specific metadata. Extends AssetMetadata
. Methods: getHeight
, getWidth
.
DAM 2.0 introduces the com.google.common.net.MediaType
class included in the Google Guava library.
Here's the class description from the Guava Javadoc.
Represents an Internet Media Type (also known as a MIME Type or Content Type). This class also supports the concept of media ranges defined by HTTP/1.1. As such, the *
character is treated as a wildcard and is used to represent any acceptable type or subtype value. A media type may not have wildcard type with a declared subtype. The *
character has no special meaning as part of a parameter. All values for type, subtype, parameter attributes or parameter values must be valid according to RFCs 2045 and 2046.
All portions of the media type that are case-insensitive (type, subtype, parameter attributes) are normalized to lowercase. The value of the charset
parameter is normalized to lowercase, but all others are left as-is.
Note that this specifically does not represent the value of the MIME Content-Type
header and as such has no support for header-specific considerations such as line folding and comments.
For media types that take a charset the predefined constants default to UTF-8 and have a "_UTF_8" suffix. To get a version without a character set, use withoutParameters()
.
Accessing the DAM API
To access AssetProviderRegistry
from your custom module, adapt your pom
and module descriptor XML files to include a dependency. You can simply inject or use components to access the AssetProviderRegistry
Code Block |
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private final AssetProviderRegistry providerRegistry;
// By Injection
@Inject
public MyFunctions(AssetProviderRegistry providerRegistry) {
this.providerRegistry = providerRegistry;
}
// Or using Components
public void myCustomMethod() {
this.providerRegistry = Components.getComponent(AssetProviderRegistry.class);
} |
AssetProvider
AssetProvider
has “capabilities” ( Javadoc resource link |
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0 | info.magnolia.dam.api.AssetProviderCapability |
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className | info.magnolia.dam.api.AssetProviderCapability |
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renderType | asynchronous |
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). Some implementations will not support all features. This can be used to drive a UI to enable/disable certain actions or UI elements. Implementations should still throw exceptions when those unsupported operations are called. (although this may not consistently be the case, for example when aggregating search results from different providers.)ItemKey
is a specific type (composed of provider id and asset id) rather than a "magic string". It is passed to most methods, rather than the assetID
string. This allows for aggregation/delegation in specialized providers.
Items, assets and folders
Item
is the main parent definition of a Folder
and an Asset
. -
Asset
is the abstract representation of an binary document: Folder
is the abstract representation of a folder that contains Asset
Implementation notes:
- To some extent,
Items,
Folders
and Assets
mimic the JCR API, but there are subtle differences that are highlighted in the Javadocs.
Items
, Folders
and Assets
are meant to be implemented "lazily". Implementations will typically keep a reference to their provider. For example, the JCR implementation simply keeps a reference to the corresponding Node
instance, and delegates to it "on demand".
An AssetRendition
is a transformation of an Asset
. The AssetRenderer
provides AssetRenditions
by bridging an Asset's
data and some type of converter.
AssetRenderer
can be provided by AssetProvider
when the conversion/translation can be managed by the AssetProvider
itself (or its underlying system), or via a "global" registry.-
AssetProviderRegistry.getRendererFor(Asset
asset,MediaType
mediaType)
, provides the entry point. It looks up in the provider then in its own registry, and bridges to other possible conversion mechanisms that are independent of the Magnolia DAM.
JCR API
The DAM JCR API classes reside in the DAM JCR module and implement the DAM API for JCR assets that are stored in the dam workspace and accessible in the Assets app <link>.
JCR classes
Javadoc resource link |
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0 | info.magnolia.dam.jcr.JcrAssetProvider |
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className | info.magnolia.dam.jcr.JcrAssetProvider |
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renderType | asynchronous |
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: AssetProvider
that delivers assets for the dam
workspace. Extends AbstractAssetProvider
and implements PathAwareAssetProvider
.
Javadoc resource link |
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0 | info.magnolia.dam.jcr.AbstractJcrItem |
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className | info.magnolia.dam.jcr.AbstractJcrItem |
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renderType | asynchronous |
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: JCR implementation of an Item
. Extends AbstractItem<JcrAssetProvider>
. Javadoc resource link |
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0 | info.magnolia.dam.jcr.JcrAsset |
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className | info.magnolia.dam.jcr.JcrAsset |
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renderType | asynchronous |
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: JCR implementation of the Asset
definition. Extends AbstractJcrItem
. Javadoc resource link |
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0 | info.magnolia.dam.jcr.JcrFolder |
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className | info.magnolia.dam.jcr.JcrFolder |
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renderType | asynchronous |
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: JCR implementation of the Folder
definition. Extends AbstractJcrItem
. Javadoc resource link |
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0 | info.magnolia.dam.jcr.AssetNodeTypes |
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className | info.magnolia.dam.jcr.AssetNodeTypes |
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renderType | asynchronous |
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: Constants and convenience methods for asset node types.
Asset
: Represents the node type mgnl:asset
. Fields: caption
, comment
, copyright
, description
, language
, master
, name
, provider_type
, subject
, title
, type
.AssetResource
: Represent the resource node bound to an Asset
. Fields: data
, extension
, filename
, height
, mimetype
, name
, ressource_name
, size
, width
.
Javadoc resource link |
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0 | info.magnolia.dam.jcr.JcrItemNodeTypePredicate |
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className | info.magnolia.dam.jcr.JcrItemNodeTypePredicate |
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renderType | asynchronous |
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: Predicate filtering assets nodes (folders and assets) based on the following Node.getPrimaryNodeType()
:
AssetNodeTypes.Asset.NAME
NodeTypes.Folder#NAME
.
Extends info.magnolia.jcr.predicate.AbstractPredicate<javax.jcr.Node>
.
Javadoc resource link |
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0 | info.magnolia.dam.jcr.DamConstants |
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className | info.magnolia.dam.jcr.DamConstants |
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renderType | asynchronous |
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: Defines commonly used constants for the DAM.JCR module. Fields: default_jcr_provider_id
, workspace
.
Custom JCR asset properties
In order to access a custom property defined under a JCR Asset node,
Javadoc resource link |
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0 | info.magnolia.dam.jcr.JcrAsset |
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className | info.magnolia.dam.jcr.JcrAsset |
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renderType | asynchronous |
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provides a public getter:
Code Block |
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/**
* JcrAsset specific implementation that lets you access a property value linked to an asset node.
* This requires an open session.
*
* @return property value Object if the property exists or null otherwise.
*/
public Object getProperty(String propertyName) {
return PropertyUtil.getPropertyValueObject(getNode(), propertyName); |
Javadoc resource link |
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0 | info.magnolia.dam.jcr.metadata.JcrDublinCore |
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className | info.magnolia.dam.jcr.metadata.JcrDublinCore |
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renderType | asynchronous |
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: JCR implementation of DublinCore
. Fields: dc_contributor
, dc_coverage
, dc_creator
, dc_publisher
, dc_relation
, dc_source
, dc_subject
, dc_type
. Methods: getContributor
, getCoverage
, getCreated
, getCreator
, getDate
, getDescription
, getFormat
, getIdentifier
, getLanguage
, getModified
, getPublisher
, getRelation
, getRights
, getSource
, getSubject
, getTitle
, getType
. Javadoc resource link |
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0 | info.magnolia.dam.jcr.metadata.JcrMagnoliaAssetMetadata |
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className | info.magnolia.dam.jcr.metadata.JcrMagnoliaAssetMetadata |
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renderType | asynchronous |
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: Base JCR implementation of the MagnoliaAssetMetadata
definition. Methods: getHeight
, getWidth
DAM templating functions
As a template developer, also have a look at damfn, a set of methods which can be used in freemarker scripts to easy access assets, asset renditions, and so on.