How to access current style in a component?

Ionic Framework ionic-v3
1

[possibly angular 2 topic]

I have a component which is essentially a canvas on which things are drawn.
The drawing depends on the size of the component.

Setting the size using an Input-parameter is easy:

    <my-component [width]="600" [height]="400"></my-component>

and in the code

    @Input() private width: number;
    @Input() private height: number;
    ...
    paint() {
        // use this.width...
    }

However, I guess it would be more natural to set the size using a style sheet.
But then how can I find out the (current) width/height in the code (e.g. in paint())?

More in general: how can I access the current style of a component in code?

Related: is it possible to use onResize(event) to find out when the size of the current component is changed (CSS changed)?