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Layer General attributes and methods (expression reference)
- width
- Return
type: Number.
Returns the width of the layer, in pixels.
It is the same as source.width.
- height
- Return
type: Number.
Returns the height of the layer, in pixels.
It is the same as source.height.
- index
- Return
type: Number.
Returns the index number of the layer in the
composition.
- parent
- Return
type: Layer, Light, or Camera.
Returns the parent Layer object
of the layer, if it has one. Example: position[0] + parent.width
- hasParent
- Return
type: Boolean.
Returns true if the layer has a parent or
false if it doesn’t.
Use the hasParent attribute
to determine if a layer has a parent layer. You can use this attribute
even if the layer has no parent layer at present. For example, the following
expression indicates that the layer to which you apply it wiggles
based on the position of the parent. If the layer has no parent,
then it wiggles based on its own position. If the layer is given
a parent later, then the behavior of the layer changes accordingly:
idx = index;
if (hasParent) {
idx = parent.index;
}
thisComp.layer(idx).position.wiggle(5,20)
- inPoint
- Return
type: Number.
Returns the In point of the layer, in seconds.
Note: In
general, the value of outPoint is greater than
the value of inPoint. However, if a layer is reversed
in time, the value of inPoint is greater than the
value of outPoint. Similarly, the value of startTime can
be greater than the value of inPoint.
- outPoint
- Return
type: Number.
Returns the Out point of the layer, in seconds.
- startTime
- Return
type: Number.
Returns the start time of the layer, in seconds.
- hasVideo
- Return
type: Boolean.
Returns true if the layer has video, or false
if it doesn’t.
- hasAudio
- Return
type: Boolean.
Returns true if the layer has audio or false
if it doesn’t.
- active
- Return
type: Boolean.
Returns true if the Video switch  is
on for the layer and the current time is in the range from the In
point of the layer to the Out point of the layer; false otherwise.
- audioActive
- Return
type: Boolean.
Returns true if the Audio switch  is
on for the layer and the current time is in the range from the In
point of the layer to the Out point of the layer; false otherwise.
- sampleImage(point, radius = [.5, .5], postEffect=true,
t=time)
- Return
type: Array [4].
Argument type: point is
an Array [2], radius is an Array [2], postEffect is
a Boolean, and t is a Number.
Samples
the color and alpha channel values of a layer and returns the average alpha-weighted
value of the pixels within the specified distance of the point as an
array: [ red, green, blue, alpha].
If postEffect is true, the sampled values are
for the layer after masks and effects on that layer have been rendered;
if postEffect is false, the sampled values are
for the layer before masks and effects have been rendered. The input
value point is in layer space; the point [0,0]
is the center of the top-left pixel in the layer. The input value radius specifies
the horizontal and vertical distance from the sample center to the
edges of the sampled rectangle. The default value samples one pixel. Note: The postEffect parameter
refers to effects applied directly to the layer, not to effects
applied indirectly, such as with an adjustment layer.
This
example samples a rectangle 4 pixels wide and 3 pixels high, centered around
a point 100 pixels down and to the right of the upper-left corner
of the layer:
thisComp.layer(1).sampleImage([100, 100], [2, 1.5])
Dan
Ebberts provides an example of how to use the sampleImage method
on his MotionScript website.
The AE Enhancers forum provides an expression
that uses the sampleImage method to measure a text
layer or shape layer and determine its effective bounding box.
Todd
Kopriva provides instructions for using the sampleImage method
and the Point Control effect to monitor colors for a specified point
during color correction on his After Effects Region of Interest blog.
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