<template>
  <div class="bg-identify" @click="refreshCode">
    <canvas :width="contentWidth" :height="contentHeight"></canvas>
  </div>
</template>
<script>
export default {
  name: "BgIdentify",
  model: {
    prop: "identifyCode",
    event: "change",
  },
  props: {
    identifyCode: {
      type: String,
      default: "1234",
    },
    fontSizeMin: {
      type: Number,
      default: 25,
    },
    fontSizeMax: {
      type: Number,
      default: 30,
    },
    backgroundColorMin: {
      type: Number,
      default: 255,
    },
    backgroundColorMax: {
      type: Number,
      default: 255,
    },
    colorMin: {
      type: Number,
      default: 0,
    },
    colorMax: {
      type: Number,
      default: 160,
    },
    lineColorMin: {
      type: Number,
      default: 100,
    },
    lineColorMax: {
      type: Number,
      default: 255,
    },
    dotColorMin: {
      type: Number,
      default: 0,
    },
    dotColorMax: {
      type: Number,
      default: 255,
    },
    contentWidth: {
      type: Number,
      default: 150,
    },
    contentHeight: {
      type: Number,
      default: 38,
    },
  },
  data() {
    return {
      identifyCodes: "1234567890",
    };
  },
  methods: {
    randomNum(min, max) {
      return Math.floor(Math.random() * (max - min) + min);
    },
    randomColor(min, max) {
      let r = this.randomNum(min, max);
      let g = this.randomNum(min, max);
      let b = this.randomNum(min, max);
      return "rgb(" + r + "," + g + "," + b + ")";
    },
    drawPic() {
      let canvas = this.$el.querySelector("canvas");
      let ctx = canvas.getContext("2d");

      ctx.textBaseline = "bottom";
      ctx.fillStyle = this.randomColor(
        this.backgroundColorMin,
        this.backgroundColorMax
      );
      ctx.fillRect(0, 0, this.contentWidth, this.contentHeight);

      for (let i = 0; i < this.identifyCode.length; i++) {
        this.drawText(ctx, this.identifyCode[i], i);
      }
      this.drawLine(ctx);
      this.drawDot(ctx);
    },
    drawText(ctx, txt, i) {
      ctx.fillStyle = this.randomColor(this.colorMin, this.colorMax);
      ctx.font =
        this.randomNum(this.fontSizeMin, this.fontSizeMax) + "px SimHei";
      let x = (i + 1) * (this.contentWidth / (this.identifyCode.length + 1));
      let y = this.randomNum(this.fontSizeMax, this.contentHeight - 5);
      var deg = this.randomNum(-45, 45);
      // 修改坐标原点和旋转角度
      ctx.translate(x, y);
      ctx.rotate((deg * Math.PI) / 180);
      ctx.fillText(txt, 0, 0);
      // 恢复坐标原点和旋转角度
      ctx.rotate((-deg * Math.PI) / 180);
      ctx.translate(-x, -y);
    },
    drawLine(ctx) {
      // 绘制干扰线
      for (let i = 0; i < 5; i++) {
        ctx.strokeStyle = this.randomColor(
          this.lineColorMin,
          this.lineColorMax
        );
        ctx.beginPath();
        ctx.moveTo(
          this.randomNum(0, this.contentWidth),
          this.randomNum(0, this.contentHeight)
        );
        ctx.lineTo(
          this.randomNum(0, this.contentWidth),
          this.randomNum(0, this.contentHeight)
        );
        ctx.stroke();
      }
    },
    drawDot(ctx) {
      // 绘制干扰点
      for (let i = 0; i < 80; i++) {
        ctx.fillStyle = this.randomColor(0, 255);
        ctx.beginPath();
        ctx.arc(
          this.randomNum(0, this.contentWidth),
          this.randomNum(0, this.contentHeight),
          1,
          0,
          2 * Math.PI
        );
        ctx.fill();
      }
    },
    refreshCode() {
      let identifyCode = "";

      for (let i = 0; i < 4; i++) {
        identifyCode += this.identifyCodes[
          this.randomNum(0, this.identifyCodes.length)
        ];
      }

      this.$emit("change", identifyCode);

      this.$nextTick(() => {
        this.drawPic();
      });
    },
  },
  mounted() {
    if (this.identifyCode) {
      this.drawPic();
    } else {
      this.refreshCode();
    }
  },
};
</script>
<style scoped>
.bg-identify {
  border: 1px solid #dcdfe6;
  box-sizing: border-box;
  border-radius: 8px;
  overflow: hidden;
}
.bg-identify > canvas {
  display: block;
}
</style>
