vue实现水印组件

Vue 水印组件实现

基础水印组件实现

创建一个基础水印组件，通过 props 接收文本、颜色、大小等参数：

<template>
  <div class="watermark-container">
    <slot></slot>
    <div class="watermark" :style="watermarkStyle"></div>
  </div>
</template>

<script>
export default {
  props: {
    text: {
      type: String,
      default: 'Watermark'
    },
    color: {
      type: String,
      default: 'rgba(0, 0, 0, 0.1)'
    },
    fontSize: {
      type: Number,
      default: 16
    },
    rotate: {
      type: Number,
      default: -30
    }
  },
  computed: {
    watermarkStyle() {
      return {
        backgroundImage: `url("${this.generateWatermark()}")`,
        position: 'absolute',
        top: 0,
        left: 0,
        width: '100%',
        height: '100%',
        pointerEvents: 'none',
        zIndex: 9999
      }
    }
  },
  methods: {
    generateWatermark() {
      const canvas = document.createElement('canvas')
      canvas.width = 200
      canvas.height = 150
      const ctx = canvas.getContext('2d')

      ctx.font = `${this.fontSize}px Arial`
      ctx.fillStyle = this.color
      ctx.textAlign = 'center'
      ctx.textBaseline = 'middle'
      ctx.translate(100, 75)
      ctx.rotate((Math.PI / 180) * this.rotate)
      ctx.fillText(this.text, 0, 0)

      return canvas.toDataURL()
    }
  }
}
</script>

<style scoped>
.watermark-container {
  position: relative;
}
</style>

防止水印被删除

添加MutationObserver监听DOM变化，防止水印被删除：

mounted() {
  this.observer = new MutationObserver((mutations) => {
    mutations.forEach((mutation) => {
      mutation.removedNodes.forEach((node) => {
        if (node === this.$el.querySelector('.watermark')) {
          this.$el.appendChild(this.createWatermark())
        }
      })
    })
  })

  this.observer.observe(this.$el, {
    childList: true
  })
},
beforeDestroy() {
  this.observer.disconnect()
},
methods: {
  createWatermark() {
    const watermark = document.createElement('div')
    watermark.className = 'watermark'
    watermark.style = this.watermarkStyle
    return watermark
  }
}

多行水印实现

修改generateWatermark方法支持多行水印：

generateWatermark() {
  const canvas = document.createElement('canvas')
  canvas.width = 400
  canvas.height = 300
  const ctx = canvas.getContext('2d')

  ctx.font = `${this.fontSize}px Arial`
  ctx.fillStyle = this.color
  ctx.textAlign = 'center'

  for (let i = 0; i < 10; i++) {
    for (let j = 0; j < 10; j++) {
      ctx.save()
      ctx.translate(i * 150, j * 100)
      ctx.rotate((Math.PI / 180) * this.rotate)
      ctx.fillText(this.text, 0, 0)
      ctx.restore()
    }
  }

  return canvas.toDataURL()
}

使用示例

在父组件中使用水印组件：

<template>
  <Watermark text="Confidential" color="rgba(0, 0, 0, 0.2)" :fontSize="20">
    <div class="content">
      <!-- 你的内容 -->
    </div>
  </Watermark>
</template>

<script>
import Watermark from './Watermark.vue'

export default {
  components: {
    Watermark
  }
}
</script>

动态更新水印

添加watch监听props变化，动态更新水印：

watch: {
  text() {
    this.updateWatermark()
  },
  color() {
    this.updateWatermark()
  },
  fontSize() {
    this.updateWatermark()
  },
  rotate() {
    this.updateWatermark()
  }
},
methods: {
  updateWatermark() {
    const watermark = this.$el.querySelector('.watermark')
    if (watermark) {
      watermark.style.backgroundImage = `url("${this.generateWatermark()}")`
    }
  }
}