HarmonyOS ImageBitmap问题

// xxx.ets
@Entry
@Component
struct ImageExample {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private img:ImageBitmap = new ImageBitmap("common/images/example.jpg")

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          this.context.drawImage( this.img,0,0,500,500,0,0,400,200)
        })
    }
    .width('100%')
    .height('100%')
  }
}

在module里绘制ImageBitmap，图片存放在当前module的ets目录下，绘制不出来，把图片放在entry module的ets目录下就可以，为什么？