Angular2 component based on canvas : how to draw inside?

I wrote a simple component based on a canvas, which I am resizing with an Input() property inside the companion class (TypeScript code). What I would like to do is to draw the canvas element inside the companion class, whose code is below : what is the simplest way to achieve that ? (Please, see the comment in the code : I would like to draw a blue rectangle inside the canvas from the constructor).

import {Component, View, Input} from 'angular2/core';

@Component({
    selector: 'chess-diagram',
})
@View({
    template: `<canvas class='chess-diag'
     [attr.width]='_size'
     [attr.height]='_size'></canvas>`,
})
export class ChessDiagram {
    private _size: number;

    constructor(){
        this._size = 150;
        // Here I would like to draw a blue rectangle inside the canvas.
    }

    get size(){
        return this._size;
    }

    @Input () set size(newValue: number){
        this._size = Math.floor(newValue);
    }
}