uniapp小程序使用canvas画布进行签名

<template>
  <view>
    <view class="wrapper">
      <view class="handBtn">
        <image @click="selectColorEvent('black', '#1A1A1A')"
          :src="selectColor === 'black' ? '/static/img/sign/color_black_selected.png' : '/static/img/sign/color_black.png'"
          :class="[selectColor === 'black' ? 'color_select' : '', 'black-select']"></image>
        <image @click="selectColorEvent('red', '#ca262a')"
          :src="selectColor === 'red' ? '/static/img/sign/color_red_selected.png' : '/static/img/sign/color_red.png'"
          :class="[selectColor === 'red' ? 'color_select' : '', 'black-select']"></image>
        <button @click="retDraw" class="delBtn">重写</button>
        <button @click="saveCanvasAsImg" class="saveBtn">保存</button>
        <button @click="previewCanvasImg" class="previewBtn">预览</button>
        <button @click="uploadCanvasImg" class="uploadBtn">上传</button>
        <button @click="subCanvas" class="subBtn">完成</button>
        <button @click="back" class="subBtn">返回</button>
      </view>
      <view class="handCenter">
        <canvas class="handWriting" :disable-scroll="true" @touchstart="uploadScaleStart" @touchmove="uploadScaleMove"
          @touchend="uploadScaleEnd" canvas-id="handWriting"></canvas>
      </view>
      <view class="handRight">
        <view class="handTitle">请签名</view>
      </view>
    </view>
  </view>
</template>

<script>
export default {
  data () {
    return {
      canvasName: 'handWriting',
      ctx: '',
      canvasWidth: 0,
      canvasHeight: 0,
      transparent: 1, // 透明度
      selectColor: 'black',
      lineColor: '#1A1A1A', // 颜色
      lineSize: 1.5, // 笔记倍数
      lineMin: 0.5, // 最小笔画半径
      lineMax: 4, // 最大笔画半径
      pressure: 1, // 默认压力
      smoothness: 60, //顺滑度，用60的距离来计算速度
      currentPoint: {},
      currentLine: [], // 当前线条
      firstTouch: true, // 第一次触发
      radius: 1, //画圆的半径
      cutArea: {
        top: 0,
        right: 0,
        bottom: 0,
        left: 0
      }, //裁剪区域
      bethelPoint: [], //保存所有线条 生成的贝塞尔点；
      lastPoint: 0,
      chirography: [], //笔迹
      currentChirography: {}, //当前笔迹
      linePrack: [] //划线轨迹 , 生成线条的实际点
    };
  },
  onLoad () {
    let canvasName = this.canvasName;
    let ctx = wx.createCanvasContext(canvasName);
    this.ctx = ctx;
    let query = wx.createSelectorQuery();
    query
      .select('.handCenter')
      .boundingClientRect(rect => {
        this.canvasWidth = rect.width;
        this.canvasHeight = rect.height;

        /* 将canvas背景设置为 白底，不设置  导出的canvas的背景为透明 */
        this.setCanvasBg('rgba(0,0,0,0)');
      })
      .exec();
  },
  methods: {
    // 笔迹开始
    uploadScaleStart (e) {
      if (e.type != 'touchstart') return false;
      let ctx = this.ctx;
      ctx.setFillStyle(this.lineColor); // 初始线条设置颜色
      ctx.setGlobalAlpha(this.transparent); // 设置半透明
      let currentPoint = {
        x: e.touches[0].x,
        y: e.touches[0].y
      };
      let currentLine = this.currentLine;
      currentLine.unshift({
        time: new Date().getTime(),
        dis: 0,
        x: currentPoint.x,
        y: currentPoint.y
      });
      this.currentPoint = currentPoint;
      // currentLine
      if (this.firstTouch) {
        this.cutArea = {
          top: currentPoint.y,
          right: currentPoint.x,
          bottom: currentPoint.y,
          left: currentPoint.x
        };
        this.firstTouch = false;
      }
      this.pointToLine(currentLine);
    },
    // 笔迹移动
    uploadScaleMove (e) {
      if (e.type != 'touchmove') return false;
      if (e.cancelable) {
        // 判断默认行为是否已经被禁用
        if (!e.defaultPrevented) {
          e.preventDefault();
        }
      }
      let point = {
        x: e.touches[0].x,
        y: e.touches[0].y
      };

      //测试裁剪
      if (point.y < this.cutArea.top) {
        this.cutArea.top = point.y;
      }
      if (point.y < 0) this.cutArea.top = 0;

      if (point.x > this.cutArea.right) {
        this.cutArea.right = point.x;
      }
      if (this.canvasWidth - point.x <= 0) {
        this.cutArea.right = this.canvasWidth;
      }
      if (point.y > this.cutArea.bottom) {
        this.cutArea.bottom = point.y;
      }
      if (this.canvasHeight - point.y <= 0) {
        this.cutArea.bottom = this.canvasHeight;
      }
      if (point.x < this.cutArea.left) {
        this.cutArea.left = point.x;
      }
      if (point.x < 0) this.cutArea.left = 0;

      this.lastPoint = this.currentPoint;
      this.currentPoint = point;

      let currentLine = this.currentLine;
      currentLine.unshift({
        time: new Date().getTime(),
        dis: this.distance(this.currentPoint, this.lastPoint),
        x: point.x,
        y: point.y
      });

      this.pointToLine(currentLine);
    },
    // 笔迹结束
    uploadScaleEnd (e) {
      if (e.type != 'touchend') return 0;
      let point = {
        x: e.changedTouches[0].x,
        y: e.changedTouches[0].y
      };
      this.lastPoint = this.currentPoint;
      this.currentPoint = point;

      let currentLine = this.currentLine;
      currentLine.unshift({
        time: new Date().getTime(),
        dis: this.distance(this.currentPoint, this.lastPoint),
        x: point.x,
        y: point.y
      });

      if (currentLine.length > 2) {
        var info = (currentLine[0].time - currentLine[currentLine.length - 1].time) / currentLine.length;
        //$("#info").text(info.toFixed(2));
      }
      //一笔结束，保存笔迹的坐标点，清空，当前笔迹
      //增加判断是否在手写区域；
      this.pointToLine(currentLine);
      var currentChirography = {
        lineSize: this.lineSize,
        lineColor: this.lineColor
      };
      var chirography = this.chirography;
      chirography.unshift(currentChirography);
      this.chirography = chirography;

      var linePrack = this.linePrack;
      linePrack.unshift(this.currentLine);
      this.linePrack = linePrack;
      this.currentLine = [];
    },
    retDraw () {
      this.ctx.clearRect(0, 0, 700, 730);
      this.ctx.draw();

      //设置canvas背景
      this.setCanvasBg('rgba(0,0,0,0)');
    },
    //画两点之间的线条；参数为:line，会绘制最近的开始的两个点；
    pointToLine (line) {
      this.calcBethelLine(line);
      return;
    },
    //计算插值的方式；
    calcBethelLine (line) {
      if (line.length <= 1) {
        line[0].r = this.radius;
        return;
      }
      let x0,
        x1,
        x2,
        y0,
        y1,
        y2,
        r0,
        r1,
        r2,
        len,
        lastRadius,
        dis = 0,
        time = 0,
        curveValue = 0.5;
      if (line.length <= 2) {
        x0 = line[1].x;
        y0 = line[1].y;
        x2 = line[1].x + (line[0].x - line[1].x) * curveValue;
        y2 = line[1].y + (line[0].y - line[1].y) * curveValue;
        //x2 = line[1].x;
        //y2 = line[1].y;
        x1 = x0 + (x2 - x0) * curveValue;
        y1 = y0 + (y2 - y0) * curveValue;
      } else {
        x0 = line[2].x + (line[1].x - line[2].x) * curveValue;
        y0 = line[2].y + (line[1].y - line[2].y) * curveValue;
        x1 = line[1].x;
        y1 = line[1].y;
        x2 = x1 + (line[0].x - x1) * curveValue;
        y2 = y1 + (line[0].y - y1) * curveValue;
      }
      //从计算公式看，三个点分别是(x0,y0),(x1,y1),(x2,y2) ；(x1,y1)这个是控制点，控制点不会落在曲线上；实际上，这个点还会手写获取的实际点，却落在曲线上
      len = this.distance({
        x: x2,
        y: y2
      }, {
        x: x0,
        y: y0
      });
      lastRadius = this.radius;
      for (let n = 0; n < line.length - 1; n++) {
        dis += line[n].dis;
        time += line[n].time - line[n + 1].time;
        if (dis > this.smoothness) break;
      }

      this.radius = Math.min((time / len) * this.pressure + this.lineMin, this.lineMax) * this.lineSize;
      line[0].r = this.radius;
      //计算笔迹半径；
      if (line.length <= 2) {
        r0 = (lastRadius + this.radius) / 2;
        r1 = r0;
        r2 = r1;
        //return;
      } else {
        r0 = (line[2].r + line[1].r) / 2;
        r1 = line[1].r;
        r2 = (line[1].r + line[0].r) / 2;
      }
      let n = 5;
      let point = [];
      for (let i = 0; i < n; i++) {
        let t = i / (n - 1);
        let x = (1 - t) * (1 - t) * x0 + 2 * t * (1 - t) * x1 + t * t * x2;
        let y = (1 - t) * (1 - t) * y0 + 2 * t * (1 - t) * y1 + t * t * y2;
        let r = lastRadius + ((this.radius - lastRadius) / n) * i;
        point.push({
          x: x,
          y: y,
          r: r
        });
        if (point.length == 3) {
          let a = this.ctaCalc(point[0].x, point[0].y, point[0].r, point[1].x, point[1].y, point[1].r, point[2].x, point[2]
            .y, point[2].r);
          a[0].color = this.lineColor;
          // let bethelPoint = this.bethelPoint;
          // bethelPoint = bethelPoint.push(a);
          this.bethelDraw(a, 1);
          point = [{
            x: x,
            y: y,
            r: r
          }];
        }
      }
      this.currentLine = line;
    },
    //求两点之间距离
    distance (a, b) {
      let x = b.x - a.x;
      let y = b.y - a.y;
      return Math.sqrt(x * x + y * y);
    },
    ctaCalc (x0, y0, r0, x1, y1, r1, x2, y2, r2) {
      let a = [],
        vx01,
        vy01,
        norm,
        n_x0,
        n_y0,
        vx21,
        vy21,
        n_x2,
        n_y2;
      vx01 = x1 - x0;
      vy01 = y1 - y0;
      norm = Math.sqrt(vx01 * vx01 + vy01 * vy01 + 0.0001) * 2;
      vx01 = (vx01 / norm) * r0;
      vy01 = (vy01 / norm) * r0;
      n_x0 = vy01;
      n_y0 = -vx01;
      vx21 = x1 - x2;
      vy21 = y1 - y2;
      norm = Math.sqrt(vx21 * vx21 + vy21 * vy21 + 0.0001) * 2;
      vx21 = (vx21 / norm) * r2;
      vy21 = (vy21 / norm) * r2;
      n_x2 = -vy21;
      n_y2 = vx21;
      a.push({
        mx: x0 + n_x0,
        my: y0 + n_y0,
        color: '#1A1A1A'
      });
      a.push({
        c1x: x1 + n_x0,
        c1y: y1 + n_y0,
        c2x: x1 + n_x2,
        c2y: y1 + n_y2,
        ex: x2 + n_x2,
        ey: y2 + n_y2
      });
      a.push({
        c1x: x2 + n_x2 - vx21,
        c1y: y2 + n_y2 - vy21,
        c2x: x2 - n_x2 - vx21,
        c2y: y2 - n_y2 - vy21,
        ex: x2 - n_x2,
        ey: y2 - n_y2
      });
      a.push({
        c1x: x1 - n_x2,
        c1y: y1 - n_y2,
        c2x: x1 - n_x0,
        c2y: y1 - n_y0,
        ex: x0 - n_x0,
        ey: y0 - n_y0
      });
      a.push({
        c1x: x0 - n_x0 - vx01,
        c1y: y0 - n_y0 - vy01,
        c2x: x0 + n_x0 - vx01,
        c2y: y0 + n_y0 - vy01,
        ex: x0 + n_x0,
        ey: y0 + n_y0
      });
      a[0].mx = a[0].mx.toFixed(1);
      a[0].mx = parseFloat(a[0].mx);
      a[0].my = a[0].my.toFixed(1);
      a[0].my = parseFloat(a[0].my);
      for (let i = 1; i < a.length; i++) {
        a[i].c1x = a[i].c1x.toFixed(1);
        a[i].c1x = parseFloat(a[i].c1x);
        a[i].c1y = a[i].c1y.toFixed(1);
        a[i].c1y = parseFloat(a[i].c1y);
        a[i].c2x = a[i].c2x.toFixed(1);
        a[i].c2x = parseFloat(a[i].c2x);
        a[i].c2y = a[i].c2y.toFixed(1);
        a[i].c2y = parseFloat(a[i].c2y);
        a[i].ex = a[i].ex.toFixed(1);
        a[i].ex = parseFloat(a[i].ex);
        a[i].ey = a[i].ey.toFixed(1);
        a[i].ey = parseFloat(a[i].ey);
      }
      return a;
    },
    bethelDraw (point, is_fill, color) {
      let ctx = this.ctx;
      ctx.beginPath();
      ctx.moveTo(point[0].mx, point[0].my);
      if (undefined != color) {
        ctx.setFillStyle(color);
        ctx.setStrokeStyle(color);
      } else {
        ctx.setFillStyle(point[0].color);
        ctx.setStrokeStyle(point[0].color);
      }
      for (let i = 1; i < point.length; i++) {
        ctx.bezierCurveTo(point[i].c1x, point[i].c1y, point[i].c2x, point[i].c2y, point[i].ex, point[i].ey);
      }
      ctx.stroke();
      if (undefined != is_fill) {
        ctx.fill(); //填充图形 ( 后绘制的图形会覆盖前面的图形, 绘制时注意先后顺序 )
      }
      ctx.draw(true);
    },
    selectColorEvent (str, color) {
      this.selectColor = str;
      this.lineColor = color;
    },
    //将Canvas内容转成 临时图片 --> cb 为回调函数 形参 tempImgPath 为 生成的图片临时路径
    canvasToImg (cb) {
      //这种写法移动端 出不来
      this.ctx.draw(true, () => {
        wx.canvasToTempFilePath({
          canvasId: 'handWriting',
          fileType: 'png',
          quality: 1, //图片质量
          success (res) {
            // console.log(res.tempFilePath, 'canvas生成图片地址');

            wx.showToast({
              title: '执行了吗？'
            });

            cb(res.tempFilePath);
          }
        });
      });
    },
    //完成
    subCanvas () {
      this.ctx.draw(true, () => {
        wx.canvasToTempFilePath({
          canvasId: 'handWriting',
          fileType: 'png',
          quality: 1, //图片质量
          success (res) {
            // console.log(res.tempFilePath, '已完成，canvas生成图片地址');
            // wx.showToast({
            // 	title: '已保存'
            // });
            //保存到系统相册
            wx.saveImageToPhotosAlbum({
              filePath: res.tempFilePath,
              success (res) {
                console.log("已完成并保存到相册");
                wx.showToast({
                  title: '已成功保存到相册',
                  duration: 2000
                });
              }
            });
          }
        });
      });
    },
    //保存到相册
    saveCanvasAsImg () {
      /*
          this.canvasToImg( tempImgPath=>{
            // console.log(tempImgPath, '临时路径');
            wx.saveImageToPhotosAlbum({
              filePath: tempImgPath,
              success(res) {
                wx.showToast({
                  title: '已保存到相册',
                  duration: 2000
                });
              }
            })
          } );
      */
      wx.canvasToTempFilePath({
        canvasId: 'handWriting',
        fileType: 'png',
        quality: 1, //图片质量
        success (res) {
          // console.log(res.tempFilePath, 'canvas生成图片地址');
          wx.saveImageToPhotosAlbum({
            filePath: res.tempFilePath,
            success (res) {
              wx.showToast({
                title: '已保存到相册',
                duration: 2000
              });
            }
          });
        }
      });
    },
    //预览
    previewCanvasImg () {
      wx.canvasToTempFilePath({
        canvasId: 'handWriting',
        fileType: 'jpg',
        quality: 1, //图片质量
        success (res) {
          // console.log(res.tempFilePath, 'canvas生成图片地址');
          wx.previewImage({
            urls: [res.tempFilePath] //预览图片 数组
          });
        }
      });

      /*	//移动端出不来  ^~^！！
          this.canvasToImg( tempImgPath=>{
            wx.previewImage({
              urls: [tempImgPath], //预览图片 数组
            })
          } );
      */
    },
    //上传
    uploadCanvasImg () {
      wx.canvasToTempFilePath({
        canvasId: 'handWriting',
        fileType: 'png',
        quality: 1, //图片质量
        success (res) {
          console.log(res.tempFilePath, '待上传服务器canvas生成图片地址');
          //上传
          wx.uploadFile({
            url: 'https://xxx/uploadSignFile', // 仅为示例，非真实的接口地址
            filePath: res.tempFilePath,
            name: 'file_signature',
            formData: {
              user: 'test'
            },
            success (res) {
              if (res.code == 1) {
                wx.showToast({
                  title: '上传成功',
                  duration: 2000
                });
              } else {
                uni.showToast({
                  title: res.message,
                  icon: "none",
                  position: 'bottom',
                  duration: 3000
                });
              }
            }
          });
        }
      });
    },
    //设置canvas背景色  不设置  导出的canvas的背景为黑色
    //@params：字符串  color
    setCanvasBg (color) {
      /* 将canvas背景设置为 白底，不设置  导出的canvas的背景默认为黑色 */
      //rect() 参数说明  矩形路径左上角的横坐标，左上角的纵坐标, 矩形路径的宽度, 矩形路径的高度
      //这里是 canvasHeight - 4 是因为下边盖住边框了，所以手动减了写
      this.ctx.rect(0, 0, this.canvasWidth, this.canvasHeight - 4);
      this.ctx.setFillStyle(color);
      this.ctx.fill(); //设置填充
      this.ctx.draw(); //开画
    },
    //返回
    back () {
      uni.reLaunch({
        url: '/pages/ucenter/ucenter'
      })
    },
  }
};
</script>

<style>
page {
  background: #fbfbfb;
  height: auto;
  overflow: hidden;
}

.wrapper {
  width: 100%;
  height: 95vh;
  margin: 30rpx 0;
  overflow: hidden;
  display: flex;
  align-content: center;
  flex-direction: row;
  justify-content: center;
  font-size: 28rpx;
}

.handWriting {
  background: #fff;
  width: 100%;
  height: 95vh;
}

.handRight {
  display: inline-flex;
  align-items: center;
}

.handCenter {
  border: 4rpx dashed #e9e9e9;
  flex: 5;
  overflow: hidden;
  box-sizing: border-box;
}

.handTitle {
  transform: rotate(90deg);
  flex: 1;
  color: #666;
}

.handBtn button {
  font-size: 28rpx;
}

.handBtn {
  height: 95vh;
  display: inline-flex;
  flex-direction: column;
  justify-content: space-between;
  align-content: space-between;
  flex: 1;
}

.delBtn {
  position: absolute;
  top: 250rpx;
  left: 0rpx;
  transform: rotate(90deg);
  color: #666;
}

.delBtn image {
  position: absolute;
  top: 13rpx;
  left: 25rpx;
}

.subBtn {
  position: absolute;
  bottom: 52rpx;
  left: -3rpx;
  display: inline-flex;
  transform: rotate(90deg);
  background: #008ef6;
  color: #fff;
  margin-bottom: 30rpx;
  text-align: center;
  justify-content: center;
}

/*Peach - 新增 - 保存*/

.saveBtn {
  position: absolute;
  top: 375rpx;
  left: 0rpx;
  transform: rotate(90deg);
  color: #666;
}

.previewBtn {
  position: absolute;
  top: 500rpx;
  left: 0rpx;
  transform: rotate(90deg);
  color: #666;
}

.uploadBtn {
  position: absolute;
  top: 625rpx;
  left: 0rpx;
  transform: rotate(90deg);
  color: #666;
}

/*Peach - 新增 - 保存*/

.black-select {
  width: 60rpx;
  height: 60rpx;
  position: absolute;
  top: 30rpx;
  left: 25rpx;
}

.black-select.color_select {
  width: 90rpx;
  height: 90rpx;
  top: 100rpx;
  left: 10rpx;
}

.red-select {
  width: 60rpx;
  height: 60rpx;
  position: absolute;
  top: 140rpx;
  left: 25rpx;
}

.red-select.color_select {
  width: 90rpx;
  height: 90rpx;
  top: 120rpx;
  left: 10rpx;
}
</style>