initialize(particle) {
    const imageTarget = this.image.getValue();

    if (typeof imageTarget === "string") {
      particle.body = {
        width: this.w,
        height: this.h,
        src: imageTarget,
        isInner: true,
        inner: true
      };
    } else {
      particle.body = imageTarget;
    }
  }
Initializes the particle's body.
@param {object} particle - The particle to initialize.