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M
melvin1817
Known Participant
March 25, 2022
Answered

Auto-scale image to always fill composition when changing its position

  • March 25, 2022
  • 2 replies
  • 9845 views

Hello,

 

I've been searching everywhere for this and haven't found how to do this.

 

What I'm trying to do is to have a composition that is for example 4k (3840 x 2160)

and to have a still image that I insert into my composition that's sometimes larger than the composition and sometimes smaller than the composition and varies in sizes like portrait, landscape and square images, regardless, I just need to create an expression on the image Scale property that will automatically fill the whole composition regardless of where I move the image.

 

Say that I animate the image position from point A to point B, I want the image to maintain a constant scale that fills the entire composition throughout the whole animation for the image.

 

Please help.

 

Thanks.

This topic has been closed for replies.
Correct answer Dan Ebberts

Never mind the reply I just posted. This expression is exactly what I needed. Thank you Dan.

 

One more thing, what change can I make to the expression you suggested to have the image maintain the same scale?

 

If I animated the position of the image from point A to point B I suppose that a calculation needs to be made to get the scale of the image at the point that is further away from the center of the composition and keep that same scale throughout the whole animation.

 

I'm trying to figure out how to do that.


You could do something like this, but it will be slow if your comp is long. (You could always do Animation > Keyframe Assistant > Convert Expression to Keyframes once you're happy with the result.)

t = Math.max(inPoint,0);
maxS = 0;
while (t < thisComp.duration){
  p = position.valueAtTime(t);
  xScale = p[0] > thisComp.width/2 ? p[0]/(width/2) : (thisComp.width - p[0])/(width/2);
  yScale = p[1] > thisComp.height/2 ? p[1]/(height/2) : (thisComp.height - p[1])/(height/2);
  s = Math.max(xScale,yScale);
  maxS = Math.max(maxS,s);
  t += thisComp.frameDuration;
}
[maxS,maxS]*100

2 replies

W
Warren Heaton10841144
Community Expert
March 26, 2022

Sounds like you want to increase the source footage size such that the width and height always exceed the Comp size.  So, use Dan Ebberts Scale expression set high enough above 100 such that the source image can pan and always filling the Comp.

Dan Ebberts
Dan Ebberts
Community Expert
March 25, 2022

Something like this will stretch (or shrink) your image layer, non-uniformly, so that the image is the same size as the comp:

[thisComp.width/width,thisComp.height/height]*100

I'm not sure if that's what you're asking for though...

    M
    melvin1817Author
    Known Participant
    March 26, 2022

    Thank you for to suggestion Dan. If the image is square in size and my composition is 3840 x 2160 the image will look stretched with the suggested expression and will not maintain its aspect ratio.

     

    Another thing is that the expression will work fine as long as the image position is not moved away from the center of the composition.

     

    What could I do to maintain the image's aspect ratio while autoscaling the image to fill the composition with the image not being at the center of the composition?

     

    I need the image to autoscale (maintaining its aspect ratio) every time I change the image's position in my composition.

    Dan Ebberts
    Dan Ebberts
    Community Expert
    April 11, 2023

    Thanks for answering. I know these methods using the GUI of after effects. But I want to apply fit to comp method by giving expression logic. Any way to do it?

     


    A scale expression like this?

    w = thisComp.width/width;
h = thisComp.height/height;
w > h ? value*h : value*w;
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