HarmonyOS app全局水印怎么实现

可参考如下代码，把水印写成一个单独的公共组件，通过容器的overlay属性来使用

@Entry
@Component
struct WaterMark {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)

  @Builder
  Watermark() {
    Canvas(this.context)
      .width("100%")
      .height("100%")
      .hitTestBehavior(HitTestMode.Transparent)
      .onReady(() => {
        this.context.fillStyle = '#10000000'
        this.context.font = "16vp"
        this.context.textAlign = "center"
        this.context.textBaseline = "middle"
        // 在这里绘制文字水印，也可以是图片水印
        for (let i = 0; i < this.context.width / 120; i++) {
          this.context.translate(120, 0)
          let j = 0
          for (; j < this.context.height / 120; j++) {
            this.context.rotate(-Math.PI / 180 * 30)
            // 此处水印数据是写死的，具体请替换为自己的水印
            this.context.fillText("水印水印水印", -60, -60)
            this.context.rotate(Math.PI / 180 * 30)
            this.context.translate(0, 120)

          }
          this.context.translate(0, -120 * j)
        }
      })
  }

  build() {
    Column() {
      Text("正文文字").fontColor("#495057")
      Image($r("app.media.testImage")).width(300)
    }
    .layoutWeight(1)
    .overlay(this.Watermark())
    .width("100%")
  }
}