AS3 using a Matrix to "scale" an object from its "center"

actionscript-3 math matrix displayobject
just_a_dude picture just_a_dude · Nov 25, 2009 · Viewed 7.7k times · Source

Here's something I'm trying to figure out concerning display objects in ActionScript3 / Flex. Let's say you have a display object who's registration point is in the top left and you want to scale it from its center (middle of the display object), How could you easily acheive this with the flash.geom.Matrix class

Thanks for your help

Answer

Aaron picture Aaron · Nov 25, 2009

This is done by translating the object to the desired center of scale/rotation, scale/rotate it and then translate it back.

You can do that with a single matrix by concatenating the matrices to get a single matrix:

var m:Matrix = new Matrix();
m.translate(-centerX, -centerY);
m.scale(scaleX, scaleY);
m.translate(centerX, centerY);

Related questions

Calculate Bounding box coordinates from a rotated rectangle

I have the coordinates of the top left point of a rectangle as well as its width, height and rotation from 0 to 180 and -0 to -180. I am trying to get the bounding coordinates of the actual box around the …

Read More
What algorithms could I use for audio volume level?

Let's say I have a slider that can go between 0 and 1. The SoundTransform.volume also ranges between 0 (silent) and 1 (full volume), but if I use a linear function, let's say SoundTransform.volume = slider.volume, the result is rather not pleasing. …

Read More
What is the best way to get the minimum or maximum value from an Array of numbers?

Let's say I have an Array of numbers: [2,3,3,4,2,2,5,6,7,2] What is the best way to find the minimum or maximum value in that Array? Right now, to get the maximum, I am looping through the Array, and resetting a variable to …

Read More