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【微信小程序canvas】实现小程序手写板用户签名(附代码)
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：
demo
wxml
<view class="wrapper"><view class="handBtn"><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>
js
data
page({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
page({onLoad () {let canvasName = this.data.canvasNamelet ctx = wx.createCanvasContext(canvasName)this.setData({ctx: ctx})var query = wx.createSelectorQuery();query.select('.handCenter').boundingClientRect(rect => {query.select('.handCenter').boundingClientRect(rect => {this.setData({this.setData({canvasWidth: rect.width,canvasWidth: rect.width,canvasHeight: rect.heightcanvasHeight: rect.height})})}).exec(); }).exec();}, },
})
事件函数
笔迹开始
// 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
// 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
// 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: []})},
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: 550rpx;left: 0rpx;transform: rotate(90deg);color: #666;
}.delBtn image {position: absolute;top: 13rpx;left: 25rpx;
}
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