Scripting – Centre Mask on Shape Layer - Adobe After Effects Expressions

Adobe After Effects Expressions

Scripting – Centre Mask on Shape Layer

Posted by Liam Carlin on March 7, 2022 at 10:17 am

Hey Guys,

I have created this snippet of code that creates a rectangle mask on any layer given it’s dimension. It works fine on all layers except Shape Layers and Text Layers. I can’t quite figure where I’m going wrong. It doesn’t centre when I thought it would. How do I center the mask?

The image show’s how it’s not cantered.

myLayer = app.project.activeItem.selectedLayers[i];

newMask = myLayer.Masks.addProperty(“ADBE Mask Atom”);

myProperty = newMask.property(“ADBE Mask Shape”);

newMask.name = “Rectangle Mask”;

newMask.maskMode = MaskMode.ADD;

myShape = myProperty.value;

myShape.vertices = [[myLayer.width,0],[0,0],[0,myLayer.height],[myLayer.width,myLayer.height]];

myShape.inTangents = [[0,0],[0,0],[0,0],[0,0]];

myShape.outTangents = [[0,0],[0,0],[0,0],[0,0]];

myShape.closed = true;

myProperty.setValue(myShape);

Thanks,
Liam

Liam Carlin replied 4 years, 2 months ago 2 Members · 4 Replies
4 Replies

Filip Vandueren
March 7, 2022 at 12:10 pm

Hi Liam, shape layers and textlayers – because they are rasterized continuosly- behave as if they always are a composition-sized layer.

Using an exprerssio with sourceRectAtTime(), you can get the correct dimensions, although for some shapes it may or may not include the stroke-width.

For example, see this question from yesterday:

https://creativecow.net/forums/thread/mask-path-shape-to-always-match-text-total-scale-and-width/

Mask Path Shape to always match text total scale and width

Liam Carlin

March 8, 2022 at 4:20 am

Thanks Filip,

That makes sense. I have previously used sourceRectAtTime(); on text layers before.

However I don’t actually know how to implement this. Are you able to see where I am going wrong.

Thanks,
Liam

app.beginUndoGroup("Undo Rectangle Mask");
            myLayer = app.project.activeItem.selectedLayers[i];
            newMask = myLayer.Masks.addProperty("ADBE Mask Atom");
            myProperty = newMask.property("ADBE Mask Shape");
            newMask.name = "Rectangle Mask";
            newMask.maskMode = MaskMode.ADD;
            myShape = myProperty.value;
            sr= myLayer.sourceRectAtTime();
            pts= [
                [sr.left, sr.top],
                [sr.left+sr.width, sr.top],
                [sr.left+sr.width, sr.top+sr.height],
                [sr.left, sr.top+sr.height],
            ];
            createPath(pts,[],[],true);
            myLayer.sr;
            myShape.vertices = [[myLayer.width,0],[0,0],[0,myLayer.height],[myLayer.width,myLayer.height]];
            myShape.inTangents = [[0,0],[0,0],[0,0],[0,0]];
            myShape.outTangents = [[0,0],[0,0],[0,0],[0,0]];
            myShape.closed = true;
            myProperty.setValue(myShape);
            app.endUndoGroup();

Filip Vandueren

March 8, 2022 at 7:19 am

Hi Liam, the example I posted was an expression, the syntax and methods are a bit different.

In a script it would be like this:

app.beginUndoGroup("Rectangle Mask");
myLayer = app.project.activeItem.selectedLayers[0];
newMask = myLayer.Masks.addProperty("ADBE Mask Atom");
myProperty = newMask.property("ADBE Mask Shape");
newMask.name = "Rectangle Mask";
newMask.maskMode = MaskMode.ADD;
myShape = myProperty.value;
sr= myLayer.sourceRectAtTime(myLayer.time,true);
myShape.vertices = [
    [sr.left, sr.top],
    [sr.left+sr.width, sr.top],
    [sr.left+sr.width, sr.top+sr.height],
    [sr.left, sr.top+sr.height],
];
myShape.closed = true;
myProperty.setValue(myShape);
app.endUndoGroup();

Liam Carlin
March 8, 2022 at 11:22 am

Thanks incredible, thank you Filip! It makes a lot of sense. Thanks for your time 👍

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Scripting – Centre Mask on Shape Layer