uniapp微信小程序开发canvas实现手写签名，预览保存上传签名以及canvas签名转base64格式

需求：小程序开发中入会的时候需要验证本人签名已计算优惠折扣，需要在入会的时候上传手写签名信息，查了下资料，有几个不同的版本，个人修改测试了两版，觉得各有千秋，第一款偶尔会有卡顿的现象（android系统，重写两次以后），但是笔记连贯，自己看起来比较舒服，第二种卡顿感较弱，但是笔迹不精确，签名看起来不精细，所以选择了第一种进行改写

代码部分

html部分功能点根据项目需求适当放开，注意btn解开的话需要看下btn的位置样式！调整下left top值至合适的位置即可（目前有切换笔迹颜色，重写，保存到本地，上传，确认签名等功能点）

js部分

data() {
      return {
        phone: '',
        nick: "",
        name: "",
        saveArr: [0, 0, 0],
        sourceCode: '',
        blackImg: require("../../static/images/sign/color_black.png"),
        blackImgSelcected: require("../../static/images/sign/color_black_selected.png"),
        redImg: require("../../static/images/sign/color_red.png"),
        redImgSelcected: require("../../static/images/sign/color_red_selected.png"),
        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
        baseAddress: ''
      }
    },

    /**
     * 生命周期函数--监听页面加载
     */
    onLoad: function(options) {
      let that = this;
      that.phone = options.phone
      that.sourceCode = options.sourceCode;
      let canvasName = this.canvasName
      let ctx = uni.createCanvasContext(canvasName)
      this.ctx = ctx
      var query = uni.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 */
        // console.log(this, 'hahah');
        this.setCanvasBg('#fff');
      }).exec();
    },

    methods: {
      /*======所有自定义函数======*/
      // 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
        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("#fff");
      },
      //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;
            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(event) {
        console.log(event)
        var color = event.currentTarget.dataset.colorValue;
        var colorSelected = event.currentTarget.dataset.color;
        this.selectColor = colorSelected
        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, () => {
          uni.canvasToTempFilePath({
            canvasId: 'handWriting',
            fileType: 'png',
            quality: 1, //图片质量
            success(res) {
              // console.log(res.tempFilePath, 'canvas生成图片地址');
              uni.showToast({
                title: '执行了吗？',
              })
              cb(res.tempFilePath);
            }
          })
        });
      },

      //完成
      subCanvas() {
        let that = this
        uni.canvasToTempFilePath({
          x: 0, // 起点坐标
          y: 0,
         // 宽高位置信息根据项目实际情况调整
          width: 343, // canvas 宽
          height: 200, // canvas 高
          canvasId: 'handWriting', // canvas id
          success(res) {
            console.log(res)
            uni.request({
              url: res.tempFilePath, //临时路径
              responseType: 'arraybuffer', //设置返回的数据格式为arraybuffer
              success: res => {
                const base64 = "data:image/png;base64," + uni.arrayBufferToBase64(res.data)
                console.log(base64)
                // that.baseAddress = base64
              }
            })
          }
        })
      },

      //保存到相册
      saveCanvasAsImg() {
        /*
        		this.canvasToImg( tempImgPath=>{
        			// console.log(tempImgPath, '临时路径');

        			uni.saveImageToPhotosAlbum({
        				filePath: tempImgPath,
        				success(res) {

        					uni.showToast({
        						title: '已保存到相册',
        						duration: 2000
        					});

        				}
        			})

        		} );
        */

        uni.canvasToTempFilePath({
          canvasId: 'handWriting',
          fileType: 'png',
          quality: 1, //图片质量
          success(res) {
            // console.log(res.tempFilePath, 'canvas生成图片地址');
            uni.saveImageToPhotosAlbum({
              filePath: res.tempFilePath,
              success(res) {
                uni.showToast({
                  title: '已保存到相册',
                  duration: 2000
                });
              }
            })
          }
        })
      },

      //预览
      previewCanvasImg() {
        uni.canvasToTempFilePath({
          canvasId: 'handWriting',
          fileType: 'jpg',
          quality: 1, //图片质量
          success(res) {
            // console.log(res.tempFilePath, 'canvas生成图片地址');
            uni.previewImage({
              urls: [res.tempFilePath], //预览图片 数组
            })
          }
        })
        /*	//移动端出不来  ^~^！！
        		this.canvasToImg( tempImgPath=>{
        			uni.previewImage({
        				urls: [tempImgPath], //预览图片 数组
        			})
        		} );
        */
      },

      //上传
      uploadCanvasImg() {
        // console.log(999);
        uni.canvasToTempFilePath({
          canvasId: 'handWriting',
          fileType: 'png',
          quality: 1, //图片质量
          success(res) {
            // console.log(res.tempFilePath, 'canvas生成图片地址');
            //上传
            uni.uploadFile({
              url: 'https://example.weixin.qq.com/upload', // 仅为示例，非真实的接口地址
              filePath: res.tempFilePath,
              name: 'file_signature',
              formData: {
                user: 'test'
              },
              success(res) {
                const data = res.data
                // do something
              }
            })
          }
        })
      },

      //设置canvas背景色  不设置  导出的canvas的背景为透明
      //@params：字符串  color
      setCanvasBg(color) {
        /* 将canvas背景设置为 白底，不设置  导出的canvas的背景为透明 */
        //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);
        // ctx.setFillStyle('red')
        this.ctx.setFillStyle(color)
        this.ctx.fill() //设置填充
        this.ctx.draw() //开画
      }
    }

获取到base64图片地址以后根据项目需求与后端交互保存信息即可

css部分

 .wrapper {
    font-size: 28rpx;
    padding: 0 30rpx;
  }

  .pageTitle {
    font-size: 30rpx;
    text-align: center;
    border-bottom: 1px solid #7f7f7f;
    padding: 60rpx 0;
    margin-bottom: 50rpx;
    color: #000;
    font-family: syNORMAL;
    font-weight: bold;
  }

  .userInfo {
    display: flex;
    justify-content: space-between;
    margin-bottom: 65rpx;
  }

  .userInfo .item {
    color: #000;
  }

  .userInfo .input {
    background-color: #f0f0f0;
    height: 60rpx;
    line-height: 60rpx;
    padding-left: 10rpx;
    margin-top: 10rpx;
  }

  .textBox {
    display: block;
    color: #777;
    margin-bottom: 65rpx;
  }

  .checkBox {
    margin-bottom: 75rpx;
    color: #777;
    padding-left: 74rpx;
    text-align: justify;
    position: relative;
    line-height: 46rpx;
  }

  .checkBox .check_1 {
    position: absolute;
    left: 0;
    top: 6rpx;
    /* width: 28rpx;height:29rpx;border: 1px solid #000; */
    padding: 1rpx;
    font-size: 24rpx;
    line-height: 24rpx;
  }

  .checkBox .mf-check {
    background-color: #000;
    color: #fff;
  }

  .checkBox .link {
    display: inline-block;
    border-bottom: 1px solid #777;
    padding: 0 4rpx;
  }

  .black-select,
  .red-select {
    display: none;
  }

  .autograph {
    margin: 240rpx 0 100rpx;
  }

  .autograph .title {
    display: flex;
    justify-content: space-between;
    margin-bottom: 20rpx;
  }

  .autograph .title label {
    color: #000;
  }

  .autograph .title .link {
    border-bottom: 1px solid #777;
    padding: 0 4rpx;
    color: #777;
  }

  .handWriting {
    background: #fff;
    width: 100%;
    height: 200px;
  }

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

  .handCenter {
    border: 1px solid #000;
    /* flex: 5; */
    overflow: hidden;
    box-sizing: border-box;
  }

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

  .handBtn button {
    font-size: 28rpx;
    border-radius: 0;
    margin: 30rpx 0 0 30rpx;
  }

  .handBtn button:after {
    border-radius: 0;
    border: none
  }

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

  .delBtn {
    /* position: absolute;
    top: 250rpx;
    left: 0rpx;*/
    /* transform: rotate(90deg); */
    color: #000;
    background-color: #fff;
    border: 1px solid #000;
  }

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

  .subBtn {
    /* position: absolute;
    bottom: 52rpx;
    left: -3rpx;*/
    /* display: inline-flex; */
    /* transform: rotate(90deg); */
    background: #000;
    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; */
    /* top: 375rpx;
    left: 0rpx; */
    /* transform: rotate(90deg); */
    color: #666;
    display: none;
  }

  .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: 30rpx;
    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; */
  }

附带第二版代码

时间稍微有点久了，找不到借鉴原素材的地址了！如有冒犯，还望海涵！有原文地址的童鞋可以留言一下 会添加超链