记录一个uniapp写的小程序的手写板，横屏，用于签名，也可竖屏

今天需要在小程序增加一个手写板的功能，但是得横向的手写纵向的保存，直接上代码，竖屏的时候不需要旋转图片

<template>
    <view class="wrapper">

        <cu-custom bgColor="bg-white" :isBack="true">
            <block slot="backText">返回</block>
            <block slot="content">{{headerTitle}}</block>
        </cu-custom>

        <view class="handBtn">
            <!-- <image catchtap="selectColorEvent" src="{{ selectColor === 'black' ? '../../public/image/index/sign/color_black_selected.png' : '../../public/image/index/sign/color_black.png' }}" class="{{ selectColor === 'black' ? 'color_select' : '' }} black-select" data-color="black"
          data-color-value="#1A1A1A"></image>
        <image catchtap="selectColorEvent" src="{{ selectColor === 'red' ? '../../public/image/index/sign/color_red_selected.png' : '../../public/image/index/sign/color_red.png' }}" class="{{ selectColor === 'red' ? 'color_select' : '' }} red-select" data-color="red"
          data-color-value="#ca262a"></image> -->
            <button @click="retDraw" class="delBtn">重写</button>
            <!-- <button @click="previewCanvasImg" class="previewBtn">预览</button> -->
            <button @click="subCanvas" class="subBtn">完成</button>
        </view>
        <view class="handCenter">
            <canvas class="handWriting" disable-scroll="true" @touchstart="uploadScaleStart"
                @touchmove="uploadScaleMove" @touchend="uploadScaleEnd" @tap="mouseDown" canvas-id="handWriting">
            </canvas>
        </view>
        <view class="handRight">
            <view class="handTitle">手写板</view>
        </view>

<canvas canvas-id="camCacnvs" class="handWriting1" :style="{position:'absolute',top:'-9999px',left:'-9999px'}"></canvas>

    </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
                　　signImg: 'signImg',
                 linePrack: [] //划线轨迹 , 生成线条的实际点
            }

        },
        onLoad() {
            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: {

            // 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;
                        // let bethelPoint = this.bethelPoint;
                        // console.log(a)
                        // console.log(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(event) {
                console.log(event)
                var color = event.currentTarget.dataset.colorValue;
                var colorSelected = event.currentTarget.dataset.color;
                this.selectColor = colorSelected,
                    this.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  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

            },
            //保存到相册
            saveCanvasAsImg() {
                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() {

                let that=this
                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');

                        // 旋转

                        that.roateImg(res.tempFilePath)
                        // uni.previewImage({
                        //     urls: [res.tempFilePath], //预览图片 数组
                        // })
                    }
                })

            },
            // 旋转图片
            roateImg(path) {
            const that =this

            const ctx = uni.createCanvasContext('camCacnvs',this);

                ctx.translate(0, this.canvasWidth);

                ctx.rotate(-90 * Math.PI / 180)

                ctx.drawImage(path, 0, 0, this.canvasWidth, this.canvasHeight)

                ctx.draw()

            setTimeout(()=> {

             uni.canvasToTempFilePath({

                  canvasId: 'camCacnvs',

                  success: function (res) {

                      var tempFilePath = res.tempFilePath;

            //           that.$emit('sumbit', res,that.Strokes)
                     // console.log(tempFilePath,999999)
                     that.base64(tempFilePath, 'jpg').then(res => {
                         console.log(res)
                     })

                      },

              fail: (err) => {

               console.log('fail', err)

              }

            },this)

            }, 200);

            },
            //上传
            uploadCanvasImg() {
                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');
                        //上传流程

                    }
                })
            },
            // 完成  导出图片
            base64(url, type) {
                return new Promise((resolve, reject) => {
                    uni.getFileSystemManager().readFile({
                        filePath: url,
                        encoding: 'base64',
                        success(res) {
                            resolve('data:image/' + type.toLocaleLowerCase() + ';base64,' + res.data)
                        },
                        fail() {
                            reject()
                        }
                    })
                })
            },
            subCanvas() {
                const that = this;
                this.ctx.draw(false, uni.canvasToTempFilePath({
                    canvasId: 'handWriting',
                    fileType: 'jpg',
                    quality: 1, //图片质量
                    success(res) {
                        let url = res.tempFilePath
                        that.roateImg(url)
                    },
                    fail() {
                        uni.showToast({
                            title: '导出失败',
                            icon: 'none',
                            duration: 2000
                        })
                    }
                }))
            }

        }

    }
</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;
    }
    .handWriting1 {
        background: #fff;
        width:95vh;
        height:calc(100vw / 7 *5);
    }

    .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;
        align-items: center;
        flex: 1;
    }

    .delBtn,
    .saveBtn,
    .previewBtn,
    .uploadBtn,
    .subBtn {
        width: 20vh !important;
        height: 70rpx;
        border: 2rpx solid #eeeeee;
        transform: rotate(90deg);
        color: #666;
    }

    .delBtn {

        position: absolute;
        bottom: 60vh;
    }

    .subBtn {
        position: absolute;
        /* bottom: 52rpx; */
        bottom: 30vh;
        display: inline-flex;
        transform: rotate(90deg);
        background: #218FFC;
        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;
    }
</style>