一.直接使用canvas实现

原文地址：//www.greatytc.com/p/800fecd63094

<template>
    <view >
        <view class="title">请在下面输入签名：</view>
        <canvas class="mycanvas" canvas-id="mycanvas" @touchstart="touchstart" @touchmove="touchmove" @touchend="touchend"></canvas>
        <view class="footer">
            <view class="left" @click="finish">完成</view>
            <view class="right" @click="clear">清除</view>
        </view>
    </view>
</template>
 
<script>
    var x = 20;
    var y =20;
    export default{
        data(){
            return {
                ctx:'',         //绘图图像
                points:[]       //路径点集合
            }
        },
        onLoad() {
            this.ctx = uni.createCanvasContext("mycanvas",this);   //创建绘图对象
             
            //设置画笔样式
            this.ctx.lineWidth = 4;
            this.ctx.lineCap = "round"
            this.ctx.lineJoin = "round"
        },
        methods:{
            //触摸开始，获取到起点
            touchstart:function(e){
                let startX = e.changedTouches[0].x;
                let startY = e.changedTouches[0].y;
                let startPoint = {X:startX,Y:startY};
                 
                /* **************************************************
                    #由于uni对canvas的实现有所不同，这里需要把起点存起来
                 * **************************************************/
                this.points.push(startPoint);
                 
                //每次触摸开始，开启新的路径
                this.ctx.beginPath();
            },
             
            //触摸移动，获取到路径点
            touchmove:function(e){
                let moveX = e.changedTouches[0].x;
                let moveY = e.changedTouches[0].y;
                let movePoint = {X:moveX,Y:moveY};
                this.points.push(movePoint);       //存点
                let len = this.points.length;
                if(len>=2){
                    this.draw();                   //绘制路径
                }
                 
            },
             
            // 触摸结束，将未绘制的点清空防止对后续路径产生干扰
            touchend:function(){                  
                this.points=[];
            },
             
            /* ***********************************************
            #   绘制笔迹
            #   1.为保证笔迹实时显示，必须在移动的同时绘制笔迹
            #   2.为保证笔迹连续，每次从路径集合中区两个点作为起点（moveTo）和终点(lineTo)
            #   3.将上一次的终点作为下一次绘制的起点（即清除第一个点）
            ************************************************ */
            draw: function() {
                let point1 = this.points[0]
                let point2 = this.points[1]
                this.points.shift()
                this.ctx.moveTo(point1.X, point1.Y)
                this.ctx.lineTo(point2.X, point2.Y)
                this.ctx.stroke()
                this.ctx.draw(true)
            },
             
            //清空画布
            clear:function(){
                let that = this;
                uni.getSystemInfo({
                    success: function(res) {
                        let canvasw = res.windowWidth;
                        let canvash = res.windowHeight;
                        that.ctx.clearRect(0, 0, canvasw, canvash);
                        that.ctx.draw(true);
                    },
                })
            },
             
            //完成绘画并保存到本地
            finish:function(){
                uni.canvasToTempFilePath({
                  canvasId: 'mycanvas',
                  success: function(res) {
                    //如果是h5页面，res.tempFilePath为base64
                    let path = res.tempFilePath;
                    uni.saveImageToPhotosAlbum({
                        filePath:path
                    })
                  }
                })
            }
        },
    }
</script>
 
<style>
    .title{
        height:50upx;
        line-height: 50upx;
        font-size: 16px;
    }
    .mycanvas{
        width: 100%;
        height: calc(100vh - 200upx);
        background-color: #ECECEC;
    }
    .footer{
        font-size: 16px;
        height: 150upx;
        display: flex;
        justify-content: space-around;
        align-items: center;
    }
    .left,.right{
        line-height: 100upx;
        height: 100upx;
        width: 250upx;
        text-align: center;
        font-weight: bold;
        color: white;
        border-radius: 5upx;
    }
    .left{
        background: #007AFF;
    }
    .right{
        background:orange;
    }
</style>

二.zwp-draw-pad插件使用

插件地址：https://ext.dcloud.net.cn/plugin?id=4329

<template>
    <view class="pageCss">
        <zwp-draw-pad ref="zwpDrawPad" :width="500" :height="500" style="background-color: #fff;"/>
        <u-button type="primary" @click="clearBtn">清除</u-button>
        <u-button type="primary" @click="backoutBtn">撤销</u-button>
        <u-button type="primary" @click="saveBtn">保存</u-button>
    </view>
</template>

<script>
    // 插件地址:https://ext.dcloud.net.cn/plugin?id=4329
    export default {
        data() {
            return {
                
            };
        },
        methods:{
            clearBtn(){
                this.$refs.zwpDrawPad.init();
            },
            backoutBtn(){
                this.$refs.zwpDrawPad.back();
            },
            saveBtn(){
                this.$refs.zwpDrawPad.save().then(res=>{
                    console.log('保存图片的地址', res.tempFilePath)
                })
            },
        },
    }
</script>

<style lang="scss">
page{
    background: #F7F8F9FF;
}
</style>

三. l-signature插件使用

插件地址：https://test-ext.dcloud.net.cn/plugin?id=4354
演示地址：http://liangei.gitee.io/limeui/#/signature

<template>
    <view>
        <view class="topBtnBox">
            <u-button type="primary" shape="circle" @click="onClick('clear')" class="btnCss btnCssClear">清除</u-button>
            <u-button type="primary" shape="circle" @click="onClick('undo')" class="btnCss btnCssBackout">撤消</u-button>
        </view>
        <view class="signatureCss" style="margin: 0 30rpx;background-color: #fff;border-radius: 20rpx;">
            <l-signature 
                disableScroll 
                ref="signatureRef" 
                :penColor="penColor" 
                :penSize="penSize" 
                :maxLineWidth="20" 
                :openSmooth="openSmooth" 
            ></l-signature>
        </view>
        <view>
            <u-button type="primary" shape="circle" @click="onClick('save')"  class="btnCss btnCssSave">保存</u-button>
            <!-- <u-button type="primary" shape="circle" @click="onClick('openSmooth')">压感关</u-button> -->
        </view>
    </view>

</template>

<script>
    // 插件地址:https://test-ext.dcloud.net.cn/plugin?id=4354
export default {
    data() {
        return {
            penColor: '#454545',
            penSize: 5,
            url: '',
            openSmooth: true
        }
    },
    methods: {
        onClick(type) {
             if(type == 'openSmooth') {
                 this.openSmooth = !this.openSmooth
                 return
             }
            if (type == 'save') {
                this.$refs.signatureRef.canvasToTempFilePath({
                    success: (res) => {
                        this.url = res.tempFilePath;
                        console.log('url',this.url);
                    }
                })
                return
            }
            if (this.$refs.signatureRef)
                this.$refs.signatureRef[type]()
        }
    }
}

</script>

<style lang="scss">
page{
    background: #F7F8F9FF;
}
.btnCss{
    font-size: 32rpx;
    width: 150rpx;
}
.topBtnBox{
    display: flex;
    margin: 32rpx;
}
.btnCssSave{
    width: 200rpx;
    margin: 80rpx auto 0;
}
.signatureCss{
    height: 750rpx;
}
</style>

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