【微信小程序canvas】实现小程序手写板用户签名(附代码)测试有效

工作中公司业务需要的微信小程序用户签字功能

先看效果图：

wxml：

<view class="wrapper"><view class="handBtn"><image catchtap="selectColorEvent" src="{{ selectColor === 'black' ? '../../images/color_black_selected.png' : '../../images/color_black.png' }}" class="{{ selectColor === 'black' ? 'color_select' : '' }} black-select" data-color="black"data-color-value="#1A1A1A"></image><image catchtap="selectColorEvent" src="{{ selectColor === 'red' ? '../../images/color_red_selected.png' : '../../images/color_red.png' }}" class="{{ selectColor === 'red' ? 'color_select' : '' }} red-select" data-color="red"data-color-value="#ca262a"></image><button catchtap="retDraw" class="delBtn">重写</button><!-- <button catchtap="subCanvas" class="subBtn">完成</button> --></view><view class="handCenter"><canvas class="handWriting" disable-scroll="true" bindtouchstart="uploadScaleStart" bindtouchmove="uploadScaleMove"bindtouchend="uploadScaleEnd" bindtap="mouseDown" canvas-id="handWriting"></canvas></view><view class="handRight"><view class="handTitle">手写板</view></view>
</view>

上面代码中所用的图片资源：

color_black.png

color_black_selected.png

color_red.png

color_red_selected.png

js:放在page里面

data: {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},

初始化:

onLoad () {let canvasName = this.data.canvasNamelet ctx = wx.createCanvasContext(canvasName)this.setData({ctx: ctx})var query = wx.createSelectorQuery();query.select('.handCenter').boundingClientRect(rect => {this.setData({canvasWidth: rect.width,canvasHeight: rect.height})}).exec();},

事件函数

// 笔迹开始uploadScaleStart (e) {if (e.type != 'touchstart') return false;let ctx = this.data.ctx;ctx.setFillStyle(this.data.lineColor);  // 初始线条设置颜色ctx.setGlobalAlpha(this.data.transparent);  // 设置半透明let currentPoint = {x: e.touches[0].x,y: e.touches[0].y}let currentLine = this.data.currentLine;currentLine.unshift({time: new Date().getTime(),dis: 0,x: currentPoint.x,y: currentPoint.y})this.setData({currentPoint,// currentLine})if (this.data.firstTouch) {this.setData({cutArea: { top: currentPoint.y, right: currentPoint.x, bottom: currentPoint.y, left: currentPoint.x },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.data.cutArea.top) {this.data.cutArea.top = point.y;}if (point.y < 0) this.data.cutArea.top = 0;if (point.x > this.data.cutArea.right) {this.data.cutArea.right = point.x;}if (this.data.canvasWidth - point.x <= 0) {this.data.cutArea.right = this.data.canvasWidth;}if (point.y > this.data.cutArea.bottom) {this.data.cutArea.bottom = point.y;}if (this.data.canvasHeight - point.y <= 0) {this.data.cutArea.bottom = this.data.canvasHeight;}if (point.x < this.data.cutArea.left) {this.data.cutArea.left = point.x;}if (point.x < 0) this.data.cutArea.left = 0;this.setData({lastPoint: this.data.currentPoint,currentPoint: point})let currentLine = this.data.currentLinecurrentLine.unshift({time: new Date().getTime(),dis: this.distance(this.data.currentPoint, this.data.lastPoint),x: point.x,y: point.y})// this.setData({//   currentLine// })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.setData({lastPoint: this.data.currentPoint,currentPoint: point})let currentLine = this.data.currentLinecurrentLine.unshift({time: new Date().getTime(),dis: this.distance(this.data.currentPoint, this.data.lastPoint),x: point.x,y: point.y})// this.setData({//   currentLine// })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.data.lineSize,lineColor: this.data.lineColor};var chirography = this.data.chirographychirography.unshift(currentChirography);this.setData({chirography})var linePrack = this.data.linePracklinePrack.unshift(this.data.currentLine);this.setData({linePrack,currentLine: []})},

其他函数：

retDraw () {this.data.ctx.clearRect(0, 0, 700, 730)this.data.ctx.draw()},//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.data.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].xy0 = line[1].yx2 = 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.data.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.data.smoothness) break;}this.setData({radius: Math.min(time / len * this.data.pressure + this.data.lineMin, this.data.lineMax) * this.data.lineSize});line[0].r = this.data.radius;//计算笔迹半径；if (line.length <= 2) {r0 = (lastRadius + this.data.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.data.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.data.lineColor;// let bethelPoint = this.data.bethelPoint;// console.log(a)// console.log(this.data.bethelPoint)// bethelPoint = bethelPoint.push(a);this.bethelDraw(a, 1);point = [{ x: x, y: y, r: r }];}}this.setData({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.data.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.setData({selectColor: colorSelected,lineColor: color})},

设置背景函数：

//设置canvas背景色  不设置  导出的canvas的背景为透明 //@params：字符串  colorsetCanvasBg(color){console.log(999);/* 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.data.ctx.rect(0, 0, this.data.canvasWidth, this.data.canvasHeight - 4);  // ctx.setFillStyle('red')this.data.ctx.setFillStyle( color )this.data.ctx.fill()  //设置填充this.data.ctx.draw()    //开画},

修改上面其他函数中的：

retDraw函数为（给canvas设置个白色的背景，不然导出的是透明的，根据自己的情况选择是否用）：

retDraw() {this.data.ctx.clearRect(0, 0, 700, 730)this.data.ctx.draw();//设置canvas背景this.setCanvasBg("#fff");},

初始化onload钩子函数中也，给canvas添加白色背景：

onLoad: function (options) {let canvasName = this.data.canvasNamelet ctx = wx.createCanvasContext(canvasName)this.setData({ctx: ctx})var query = wx.createSelectorQuery();query.select('.handCenter').boundingClientRect( rect => {this.setData({canvasWidth: rect.width,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();},

在原代码中增加保存、预览、上传等功能：

保存到相册：

//保存到相册saveCanvasAsImg(){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:

//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})}})},

上传：

//上传uploadCanvasImg() {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');//上传wx.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}})}})},

wxss:

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;
}.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;
}

实现微信小程序手写板用户签名(附代码)预览、保存、上传均有，三种手写板方法_下载https://download.csdn.net/download/qq_41211900/11166644

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