微信小程序实现手写板

本文实例为大家分享了微信小程序实现手写板的具体代码，供大家参考，具体内容如下

<!-- wxml -->
<view class="hxt-flex-column"> ? ? ? ?
<view class="hxt-flex" style="font-size: 30rpx;padding: 30rpx;">
? ? ? ? ? <view>
? ? ? ? ? ? <text wx:if="{{!tempFilePath}}">尚未签名，请点击“签名”开始签字</text>
? ? ? ? ? ? <image wx:if="{{tempFilePath}}" src="{{tempFilePath}}"></image>
? ? ? ? ? </view>
? ? ? ? ? <view style="color: #319987;" bindtap="autograph">
? ? ? ? ? ? <van-icon name="edit" />签名
? ? ? ? ? </view>
? ? ? ? </view>
</view>
<page-container show="{{show}}" style="height: 100vh;width: 100vm;" position="center" bind:clickoverlay="closeSheet" bind:afterleave="closeSheet">
? <view class="wrapper">
? ? <view class="handBtn">
? ? ? <image catchtap="selectColorEvent" src="{{ selectColor === 'black' ? '//img.jbzj.com/file_images/article/202207/20227875050855.png' : '//img.jbzj.com/file_images/article/202207/20227875216713.png' }}" class="{{ selectColor === 'black' ? 'color_select' : '' }} black-select" data-color="black" data-color-value="#1A1A1A"></image>
? ? ? <image catchtap="selectColorEvent" src="{{ selectColor === 'red' ? '//img.jbzj.com/file_images/article/202207/20227875248330.png' : '//img.jbzj.com/file_images/article/202207/20227875312284.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="saveCanvasAsImg" 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>
</page-container>

js:

// index.js
var QQMapWX = require('utils/qqmap-wx-jssdk.js');
var qqmapsdk = new QQMapWX({
? key: 'H2RBZ-MGCC3-N4G3I-YCX6A-IKB5J-WIBTW' // 必填
});
Page({
? data: {
? ? show: false,
? ? 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.data.canvasName
? ? let 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();
? },
? // 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.currentLine
? ? currentLine.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.currentLine
? ? currentLine.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.chirography
? ? chirography.unshift(currentChirography);
? ? this.setData({
? ? ? chirography
? ? })
? ? var linePrack = this.data.linePrack
? ? linePrack.unshift(this.data.currentLine);
? ? this.setData({
? ? ? linePrack,
? ? ? currentLine: []
? ? })
? }, 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].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.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
? ? })
? },
? //保存到相册
? saveCanvasAsImg() {
? ? var _this = this;
? ? wx.canvasToTempFilePath({
? ? ? canvasId: 'handWriting',
? ? ? fileType: 'png',
? ? ? destWidth: 600,
? ? ? destHeight: 300,
? ? ? quality: 1, //图片质量
? ? ? success(res) {
? ? ? ? console.log(res.tempFilePath, 'canvas生成图片地址');
? ? ? ? _this.setData({ show: false,tempFilePath: res.tempFilePath});
? ? ? }
? ? })
? },
? , autograph: function (e) {
? ? this.setData({ show: true })
? }
? , closeSheet: function (e) {
? ? this.setData({ show: false })
? }
})

/*wxss*/
.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;
}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。

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