HarmonyOS/OpenHarmony application development - ArkTS canvas component CanvasRenderingContext2D object (6)

globalCompositeOperation 
property and method

code:

 

// xxx.ets
@Entry
@Component
struct GlobalCompositeOperation {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  
  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          this.context.fillStyle = 'rgb(255,0,0)'
          this.context.fillRect(20, 20, 50, 50)
          this.context.globalCompositeOperation = 'source-over'
          this.context.fillStyle = 'rgb(0,0,255)'
          this.context.fillRect(50, 50, 50, 50)
          this.context.fillStyle = 'rgb(255,0,0)'
          this.context.fillRect(120, 20, 50, 50)
          this.context.globalCompositeOperation = 'destination-over'
          this.context.fillStyle = 'rgb(0,0,255)'
          this.context.fillRect(150, 50, 50, 50)
      })
    }
    .width('100%')
    .height('100%')
  }
}

Effect

shadowBlur
code

// xxx.ets
@Entry
@Component
struct ShadowBlur {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  
  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          this.context.shadowBlur = 30
          this.context.shadowColor = 'rgb(0,0,0)'
          this.context.fillStyle = 'rgb(255,0,0)'
          this.context.fillRect(20, 20, 100, 80)
      })
    }
    .width('100%')
    .height('100%')
  }
}

Effect