getTexture(region) {
		if (typeof region === "object" && typeof region.texture === "string") {
			return this.sources.get(region.texture);
		} else {
			return this.sources.get(this.activeAtlas);
		}
	}
return the source texture for the given region (or default one if none specified)
@param {object} [region] - region name in case of multipack textures
@returns {HTMLImageElement|HTMLCanvasElement}