While
creating a Pixel Bender shader kernel, the author can specify metadata about
the shader in the Pixel Bender source code. While using a shader
in ActionScript, you can examine the shader and extract its metadata.
When you create a Shader instance and link it to a Pixel Bender
shader, a ShaderData object containing data about the shader is
created and stored in the Shader object’s
data
property.
The ShaderData class doesn’t define any properties of its own. However,
at run time a property is dynamically added to the ShaderData object
for each metadata value defined in the shader source code. The name
given to each property is the same as the name specified in the metadata.
For example, suppose the source code of a Pixel Bender shader includes
the following metadata definition:
namespace : "Adobe::Example";
vendor : "Bob Jones";
version : 1;
description : "Creates a version of the specified image with the specified brightness.";
The ShaderData object created for that shader is created with
the following properties and values:
-
namespace
(String):
"Adobe::Example"
-
vendor
(String):
"Bob Jones"
-
version
(String):
"1"
-
description
(String):
"Creates a version of the specified image with the specified brightness"
Because metadata properties are dynamically added to the ShaderData
object, you can use a
for..in
loop to examine the
ShaderData object. Using this technique you can find out whether
the shader has any metadata and what the metadata values are. In
addition to metadata properties, a ShaderData object can have properties
representing inputs and parameters that are defined in the shader.
When you use a
for..in
loop to examine a ShaderData
object, check the data type of each property to determine whether
the property is an input (a ShaderInput instance), a parameter (a
ShaderParameter instance), or a metadata value (a String instance).
The following example shows how to use a
for..in
loop
to examine the dynamic properties of a shader’s
data
property.
Each metadata value is added to a Vector instance named
metadata
.
Note that this example assumes a Shader instance named
myShader
is
already created:
var shaderData:ShaderData = myShader.data;
var metadata:Vector.<String> = new Vector.<String>();
for (var prop:String in shaderData)
{
if (!(shaderData[prop] is ShaderInput) && !(shaderData[prop] is ShaderParameter))
{
metadata[metadata.length] = shaderData[prop];
}
}
// do something with the metadata
For a version of this example that also extracts shader inputs
and parameters, see
Identifying shader inputs and parameters
. For more information about
input and parameter properties, see
Specifying shader input and parameter values
.
