• canvas图片旋转扩展出原生JS实现移动端横竖屏手写签名示例

    前提知识

    canvas是提供了各种各样的接口去控制画布，比如旋转rotate方法。

    这里的旋转并不是真的把这个画布旋转了，例如ctx.rotate(90 * Math.PI / 180)顺时针旋转90°了，并不是说我们在页面上就会看到canvas旋转了90°。我们可以理解为其实canvas是有两个部分组成的，一个是肉眼看得到的画布，一个是用于操作的虚拟画布，我们所有在虚拟画布上的动作都会映射到真实画布中去。

    旋转画布的原点默认画布的左上角（0,0）点，如图：

    总结下，常用画布相关的知识点：

    • 1.旋转画布的原点默认画布的左上角（0,0）点，可以使用ctx.translate(x, y)方法移动画布原点；
    • 2.ctx.rotate(90 * Math.PI / 180)顺时针旋转90°，ctx.rotate(-90 * Math.PI / 180)逆时针旋转90°；
    • 3.context.drawImage方法的使用，如下：

    语法一-在画布上定位图像：

    context.drawImage(img,x,y);

    语法二-在画布上定位图像，并规定图像的宽度和高度：

    context.drawImage(img,x,y,width,height);

    语法三-剪切图像，并在画布上定位被剪切的部分：

    context.drawImage(img,sx,sy,swidth,sheight,x,y,width,height);

    参数值：

    参数描述
    img 规定要使用的图像、画布或视频。
    sx 可选。开始剪切的 x 坐标位置。
    sy 可选。开始剪切的 y 坐标位置。
    swidth 可选。被剪切图像的宽度。
    sheight 可选。被剪切图像的高度。
    x 在画布上放置图像的 x 坐标位置。
    y 在画布上放置图像的 y 坐标位置。
    width 可选。要使用的图像的宽度。（伸展或缩小图像）
    height 可选。要使用的图像的高度。（伸展或缩小图像）

    参考地址：《HTML5 canvas drawImage() 方法》。

    • 4.会使用canvas的save和restore方法。

    save：用来保存Canvas的状态。save之后，可以调用Canvas的平移、放缩、旋转、错切、裁剪等操作。 restore：用来恢复Canvas之前保存的状态。防止save后对Canvas执行的操作对后续的绘制有影响。

    示例：

    ar canvas = document.getElementById("canvas");  
var context = canvas.getContext('2d');  
context.lineWidth = "10";  
context.strokeStyle = "#fe9901";  
context.translate(canvas.width / 2, canvas.height / 2);  
context.rotate( 30 / 180 * Math.PI);  
context.beginPath();  
context.moveTo(0, -180);  
context.lineTo(0, -200);  
context.stroke();  
  
context.rotate( 30 / 180 * Math.PI);  
context.beginPath();  
context.moveTo(0, -140);  
context.lineTo(0, -160);  
context.stroke();

    没有使用save，restore，第一次绘制时画布旋转30度，然后按照坐标绘制直线，第二次绘制在第一次基础上继续绘制，旋转30度，实际上相对于起点，旋转了60. 所以画出来两条直线不在一条指线上。

    context.save();  
context.rotate( 30 / 180 * Math.PI);  
context.beginPath();  
context.moveTo(0, -180);  
context.lineTo(0, -200);  
context.stroke();  
context.restore();  
  
context.rotate( 30 / 180 * Math.PI);  
context.beginPath();  
context.moveTo(0, -140);  
context.lineTo(0, -160);  
context.stroke();

    第二次绘制加入save和restore， 再第一次绘制后，resore到起始状态，也就是现在画布又回到了0度位置，而不是30度，所以第二次绘制是从0度开始绘制，绘制出来应该和第一次的直线在一条指线上。

     canvas移动与旋转示例

    首先我们用如下图片绘制到canvas画布中，然后我们要保存旋转后的图片，如图所示。

    画布图片：

    旋转后保存的图片：

    demo代码：

    <!DOCTYPE html>
<html>
    <head>
        <title>canvas移动与旋转</title>
        <meta charset="utf-8">
        <meta name="viewport" content="width=device-width,initial-scale=1.0,minimum-scale=1.0,maximum-scale=1.0,user-scalable=no" />
        <style>
            html,body {
                padding:0;
                margin:0;
                width: 100%;
                height: 100%;
            }
            .canvasparent {
                width: 100px;
                height: 200px;
                margin: 100px auto 20px;
                border: 1px solid #cccccc;
                box-sizing: content-box;
                position: relative;
            }
            #canvas {
                position: absolute;
                top: 0;
                left: 0;
                width: 100px;
                height: 200px;
                border-top-left-radius: 30px;
            }
            
        </style>
    </head>
    <body>
        <div class="canvasparent" id="canvasparent">
            <canvas id="canvas"></canvas>
        </div>
        <img src="" id="img" style="border: 1px solid #ccc"/>
    <script>
        var canvas = document.getElementById('canvas');
        var ctx = canvas.getContext('2d');
        canvas.width = 100;
        canvas.height = 200;
        var img = new Image();
        img.src = './images/1.jpg';
        img.onload = function() {
            ctx.drawImage(img,0,0,100,200);
            var imgSRC = canvas.toDataURL('image/png', 1);
            var img2 = new Image();
            img2.src = imgSRC;
            img2.onload = function() {
                var clipCanvas = document.createElement("canvas");
                var ctx2 = clipCanvas.getContext('2d');
                clipCanvas.width = 200;
                clipCanvas.height = 100;
                ctx2.translate(0,100);
                ctx2.rotate(-90 * Math.PI / 180);
                ctx2.drawImage(img2,0,0,100,200);
                var imgSRC2 = clipCanvas.toDataURL('image/png', 1);
                document.getElementById('img').src = imgSRC2;
            }    
        }
    </script>
</html>

    当然上面使用了translate和rotate，我们只有rotate和drawImage也是可以的，修改的JS代码如下：

    var canvas = document.getElementById('canvas');
        var ctx = canvas.getContext('2d');
        canvas.width = 100;
        canvas.height = 200;
        var img = new Image();
        img.src = './images/1.jpg';
        img.onload = function() {
            ctx.drawImage(img,0,0,100,200);
            var imgSRC = canvas.toDataURL('image/png', 1);
            var img2 = new Image();
            img2.src = imgSRC;
            img2.onload = function() {
                var clipCanvas = document.createElement("canvas");
                var ctx2 = clipCanvas.getContext('2d');
                clipCanvas.width = 200;
                clipCanvas.height = 100;
                ctx2.rotate(-90 * Math.PI / 180);
                ctx2.drawImage(img2,-100,0,100,200);
                var imgSRC2 = clipCanvas.toDataURL('image/png', 1);
                document.getElementById('img').src = imgSRC2;
            }    
        }

     手写签名demo

    html代码：

    <body>
        <div class="app-container" style="padding-top: 100px;">
            <button id="signature-button">开始手写签名</button>
            <div class="signature-result__img">
                <img src="" id="signature-img" alt="手写签名图片预览"/>
            </div>
        </div>
        <div id="signature-pop">
            <div id="signature-container">
                <div class="demo-top-info" id="rotate-container">
                    <div class="return" id="return">返回</div>
                    <div class="signature-title text-center">手写签名</div>
                </div>
                <div class="canvas-container">
                    <div class="canvas-parent">
                        <canvas id="canvas"></canvas>
                    </div>
                </div>
                <div class="demo-bottom-info">
                    <div id="clean_canvas">清空</div>
                    <div id="sure_canvas">确认</div>
                </div>
            </div>
            <canvas id="canvas2"></canvas>
        </div>
        
    </body>

    CSS代码：

    html,body {
                padding:0;
                margin:0;
                width: 100%;
                height: 100%;
            }
            .text-center {
                text-align: center;
            }
            #signature-button {
                display: block;
                margin: 0 auto;
            }
            #signature-img {
                width: 200px;
                height: 100px;
                margin: 10px auto;
                display: none;
            }
            #signature-pop {
                position: fixed;
                background-color: #fff;
                top:0;
                left:0;
                bottom:0;
                right:0;
                width: 100%;
                height: 100%;
                display: none;
            }
            #signature-container {
                width: 100%;
                height: 100%;
            }
            .demo-top-info {
                position: absolute;
                top: 0;
                left: 0;
                width: 100%;
                height: 40px;
                background: #cccccc;
                box-sizing: border-box;
                text-align: center;
            }
            .demo-top-info .return {
                padding-left: 5px;
                height: 40px;
                line-height: 40px;
                position: absolute;
                left: 10px;
                display: inline-block;
            }
            .signature-title {
                height: 40px;
                line-height: 40px;
                display: inline-block;
            }
            .canvas-container {
                width: 100%;
                height: 100%;
                background-color: #ffffff;
                box-sizing: border-box;
                padding: 40px 0 40px 0;
            }
            .canvas-parent {
                width: 100%;
                height: 100%;
            }
            .demo-bottom-info {
                position: absolute;
                bottom:0;
                left:0;
                width: 100%;
                height: 40px;
                background: #cccccc;
                padding: 0 2%;
                box-sizing: border-box;
                overflow: hidden;
            }
            #clean_canvas {
                float: left;
                font-size: 18px;
                margin-top: 2px;
                background: #f8f8f8;
                border: 1px solid #ddd;
                padding: 5px 10px;
                border-radius: 4px;
            }
            #sure_canvas {
                float: right;
                padding: 3px 0;
                background: #00005F;
                padding: 5px 10px;
                border: 1px solid #00005F;
                border-radius: 4px;
                color: #fff;
                margin-top: 3px;
            }    
            #canvas2 {
                position: absolute;
                top: 0;
                left:0;
                z-index: 999;
                margin-left: 40px;
            }

    JS代码：

    // 手绘签名类
        var SignatureClass = (function(){
            //获取当前位置(返回px)
            function getStyle(obj, attr) {
                if (obj.currentStyle) {
                    return obj.currentStyle[attr];
                } else {
                    return getComputedStyle(obj, false)[attr];
                }
            }
            
            function Signatrue(options) {
                this.cavnas = null;
                this.ctx = null;
                this.maxparams = {};
                this.minparams = {};
                this.entershuping = true; //是否是竖屏 true=是
                this.firstTouch = true; // 第一次点击或touch
                this.allowSubmit = false; // 是否手写了内容 是=才能提交 否=不能提交
                if(options === void 0) {
                    options = {};
                }
                this.options = options;
            }
            
            // 初始化
            Signatrue.prototype.init = function() {
                var self = this;
                console.log(getStyle(document.getElementById("rotate-container"), "height")); // 不知道为什么加，否则有些Apple出问题
                this.hengshuping();
                this.clear();
                this.submit();
                
                window.addEventListener('resize',function() {
                    self.hengshuping();
                },false);
            }
            
            // 判断横竖屏
            Signatrue.prototype.hengshuping = function() {
                if (window.orientation == 90 || window.orientation == -90) {
                    this.entershuping = false; // 横屏
                    document.getElementById("canvas2").style.display = "none";
                    document.getElementById("canvas").style.display = "block";
                    this.canvas = document.getElementById("canvas");
                    this.ctx = this.canvas.getContext("2d");
                    this.ctx.lineWidth = 1;
                    this.ctx.strokeStyle = "#000000";
                    this.drawEvent();
                    document.querySelector("#signature-container").style.width = window.innerWidth + "px";
                    document.querySelector("#signature-container").style.height = window.innerHeight + "px";
                    this.canvas.height = parseInt(getStyle(document.getElementById("canvas").parentNode, 'height'));
                    this.canvas.width = parseInt(getStyle(document.getElementById("canvas").parentNode, 'width'));
                    document.querySelector("#signature-container").style.transform = "rotate(0deg)";
                    document.querySelector("#signature-container").style.transformOrigin = "0 0";
                    document.querySelector("#signature-container").style.marginLeft = "0px";
                } else { // 竖屏
                    this.entershuping = true;
                    document.getElementById("canvas").style.display = "none";
                    document.getElementById("canvas2").style.display = "block";
                    this.canvas = document.getElementById("canvas2");
                    this.ctx = this.canvas.getContext("2d");
                    this.canvas.height = window.innerHeight;
                    this.canvas.width = window.innerWidth - 40 - 40;
                    this.ctx.lineWidth = 1;
                    this.ctx.strokeStyle = "#000000";
                    this.drawEvent();
                    document.querySelector("#signature-container").style.width = window.innerHeight + "px";
                    document.querySelector("#signature-container").style.height = window.innerWidth + "px";
                    document.querySelector("#signature-container").style.transform = "rotate(90deg)";
                    document.querySelector("#signature-container").style.transformOrigin = "0 0";
                    document.querySelector("#signature-container").style.marginLeft = window.innerWidth + "px";
                }
            }
            
            // 绘画事件
            Signatrue.prototype.drawEvent = function() {
                var self = this;
                this.canvas.addEventListener("touchstart", function(evt) {
                    var oEvent = evt || event;
                    oEvent.preventDefault();
                    var position = self.pos(oEvent);
                    self.ctx.beginPath();
                    self.ctx.moveTo(position.x, position.y);
                    if (self.firstTouch) {
                        self.minparams = {
                            x: position.x,
                            y: position.y
                        };
                        self.maxparams = {
                            x: position.x,
                            y: position.y
                        };
                        self.firstTouch = false;
                    } else {
                        self.judgeSize(position);
                    }
                    self.canvas.addEventListener("touchmove", touchmove, false)
                
                    function touchmove(evt) {
                        var oEvent = evt || event;
                        oEvent.preventDefault();
                        var position = self.pos(oEvent);
                        self.ctx.lineTo(position.x, position.y);
                        self.judgeSize(position);
                        self.ctx.stroke();
                    }
                    document.addEventListener("touchend", touchend, false)
                
                    function touchend(evt) {
                        var oEvent = evt || event;
                        oEvent.preventDefault();
                        self.allowSubmit = true;
                        self.canvas.removeEventListener("touchmove", touchmove);
                        document.removeEventListener("touchend", touchend);
                    }
                })
            }
            
            // 清空画笔
            Signatrue.prototype.clear = function() {
                var self = this;
                document.getElementById("clean_canvas").addEventListener("click", function() {
                    self.ctx.clearRect(0, 0, self.canvas.width, self.canvas.height);
                    self.allowSubmit = false;
                })
            }
            
            // 提交画笔内容
            Signatrue.prototype.submit = function() {
                var self = this;
                document.getElementById("sure_canvas").addEventListener("click", function() {
                    if (self.allowSubmit) {
                        var imgSRC = self.canvas.toDataURL('image/png', 1);
                        var img = new Image();
                        img.src = imgSRC;
                        self.ctx.clearRect(0, 0, self.canvas.width, self.canvas.height);
                        img.onload = function() {
                            var width = self.maxparams.x - self.minparams.x;
                            var height = self.maxparams.y - self.minparams.y;
                            var targetWidth = 200;
                            var targetHeight = 100;
                            var clipCanvas = document.createElement("canvas");
                            clipCanvas.width = targetWidth;
                            clipCanvas.height = targetHeight;
                            var ctx2 = clipCanvas.getContext("2d");
                            if (self.entershuping) {
                                ctx2.translate(0, targetHeight);
                                ctx2.rotate(-90 * Math.PI / 180);
                                ctx2.drawImage(img, self.minparams.x, self.minparams.y, width, height, 0, 0, targetHeight, targetWidth);
                            } else {
                                ctx2.drawImage(img, self.minparams.x, self.minparams.y, width, height, 0, 0, targetWidth, targetHeight);
                            }
                            var imgSRC2 = clipCanvas.toDataURL('image/png', 1);
                            if(self.options && self.options.callback && typeof self.options.callback == 'function') {
                                self.options.callback(imgSRC2);
                            }
                            self.canvas = null;
                            self.ctx = null;
                            ctx2 = null;
                            clipCanvas = null;
                            
                        }
                    } else {
                        alert("没有手写签名，不能提交!")
                    }
                })
            }
            
            
            // 获取当前位置
            Signatrue.prototype.pos = function(event) {
                var x = event.touches[0].pageX - event.target.offsetLeft;
                var y = event.touches[0].pageY - event.target.offsetTop;
                return {
                    x: x,
                    y: y
                };
            }
            
            // 优化画笔界限，去掉空白区域
            Signatrue.prototype.judgeSize = function(value) {
                if (this.minparams.x > value.x) {
                    this.minparams.x = value.x;
                }
                if (this.maxparams.x < value.x) {
                    this.maxparams.x = value.x;
                }
                if (this.minparams.y > value.y) {
                    this.minparams.y = value.y;
                }
                if (this.maxparams.y < value.y) {
                    this.maxparams.y = value.y;
                }
            }
            
            return Signatrue;
        })();
        
        
        // 点击去手写签名-展示手写签名弹框
        document.getElementById('signature-button').addEventListener('click',function(){
            document.getElementById('signature-pop').style.display = 'block';
            var signatrueDraw = new SignatureClass({
                callback: function(base64) {
                    document.getElementById('signature-img').src = base64;
                    document.getElementById('signature-pop').style.display = 'none';
                    document.getElementById('signature-img').style.display = 'block';
                }
            });
            signatrueDraw.init();

        },false);
        
        // 点击弹框返回
        document.getElementById('return').addEventListener('click',function(){
            document.getElementById('signature-pop').style.display = 'none';
        },false);

    完整的demo代码：

    <!DOCTYPE html>
<html>
    <head>
        <title>手写签名demo</title>
        <meta charset="utf-8">
        <meta name="viewport" content="width=device-width,initial-scale=1.0,minimum-scale=1.0,maximum-scale=1.0,user-scalable=no" />
        <style>
            html,body {
                padding:0;
                margin:0;
                width: 100%;
                height: 100%;
            }
            .text-center {
                text-align: center;
            }
            #signature-button {
                display: block;
                margin: 0 auto;
            }
            #signature-img {
                width: 200px;
                height: 100px;
                margin: 10px auto;
                display: none;
            }
            #signature-pop {
                position: fixed;
                background-color: #fff;
                top:0;
                left:0;
                bottom:0;
                right:0;
                width: 100%;
                height: 100%;
                display: none;
            }
            #signature-container {
                width: 100%;
                height: 100%;
            }
            .demo-top-info {
                position: absolute;
                top: 0;
                left: 0;
                width: 100%;
                height: 40px;
                background: #cccccc;
                box-sizing: border-box;
                text-align: center;
            }
            .demo-top-info .return {
                padding-left: 5px;
                height: 40px;
                line-height: 40px;
                position: absolute;
                left: 10px;
                display: inline-block;
            }
            .signature-title {
                height: 40px;
                line-height: 40px;
                display: inline-block;
            }
            .canvas-container {
                width: 100%;
                height: 100%;
                background-color: #ffffff;
                box-sizing: border-box;
                padding: 40px 0 40px 0;
            }
            .canvas-parent {
                width: 100%;
                height: 100%;
            }
            .demo-bottom-info {
                position: absolute;
                bottom:0;
                left:0;
                width: 100%;
                height: 40px;
                background: #cccccc;
                padding: 0 2%;
                box-sizing: border-box;
                overflow: hidden;
            }
            #clean_canvas {
                float: left;
                font-size: 18px;
                margin-top: 2px;
                background: #f8f8f8;
                border: 1px solid #ddd;
                padding: 5px 10px;
                border-radius: 4px;
            }
            #sure_canvas {
                float: right;
                padding: 3px 0;
                background: #00005F;
                padding: 5px 10px;
                border: 1px solid #00005F;
                border-radius: 4px;
                color: #fff;
                margin-top: 3px;
            }    
            #canvas2 {
                position: absolute;
                top: 0;
                left:0;
                z-index: 999;
                margin-left: 40px;
            }
        </style>
    </head>
    <body>
        <div class="app-container" style="padding-top: 100px;">
            <button id="signature-button">开始手写签名</button>
            <div class="signature-result__img">
                <img src="" id="signature-img" alt="手写签名图片预览"/>
            </div>
        </div>
        <div id="signature-pop">
            <div id="signature-container">
                <div class="demo-top-info" id="rotate-container">
                    <div class="return" id="return">返回</div>
                    <div class="signature-title text-center">手写签名</div>
                </div>
                <div class="canvas-container">
                    <div class="canvas-parent">
                        <canvas id="canvas"></canvas>
                    </div>
                </div>
                <div class="demo-bottom-info">
                    <div id="clean_canvas">清空</div>
                    <div id="sure_canvas">确认</div>
                </div>
            </div>
            <canvas id="canvas2"></canvas>
        </div>
        
    </body>
    <script type="text/javascript">
        
        // 手绘签名类
        var SignatureClass = (function(){
            //获取当前位置(返回px)
            function getStyle(obj, attr) {
                if (obj.currentStyle) {
                    return obj.currentStyle[attr];
                } else {
                    return getComputedStyle(obj, false)[attr];
                }
            }
            
            function Signatrue(options) {
                this.cavnas = null;
                this.ctx = null;
                this.maxparams = {};
                this.minparams = {};
                this.entershuping = true; //是否是竖屏 true=是
                this.firstTouch = true; // 第一次点击或touch
                this.allowSubmit = false; // 是否手写了内容 是=才能提交 否=不能提交
                if(options === void 0) {
                    options = {};
                }
                this.options = options;
            }
            
            // 初始化
            Signatrue.prototype.init = function() {
                var self = this;
                console.log(getStyle(document.getElementById("rotate-container"), "height")); // 不知道为什么加，否则有些Apple出问题
                this.hengshuping();
                this.clear();
                this.submit();
                
                window.addEventListener('resize',function() {
                    self.hengshuping();
                },false);
            }
            
            // 判断横竖屏
            Signatrue.prototype.hengshuping = function() {
                if (window.orientation == 90 || window.orientation == -90) {
                    this.entershuping = false; // 横屏
                    document.getElementById("canvas2").style.display = "none";
                    document.getElementById("canvas").style.display = "block";
                    this.canvas = document.getElementById("canvas");
                    this.ctx = this.canvas.getContext("2d");
                    this.ctx.lineWidth = 1;
                    this.ctx.strokeStyle = "#000000";
                    this.drawEvent();
                    document.querySelector("#signature-container").style.width = window.innerWidth + "px";
                    document.querySelector("#signature-container").style.height = window.innerHeight + "px";
                    this.canvas.height = parseInt(getStyle(document.getElementById("canvas").parentNode, 'height'));
                    this.canvas.width = parseInt(getStyle(document.getElementById("canvas").parentNode, 'width'));
                    document.querySelector("#signature-container").style.transform = "rotate(0deg)";
                    document.querySelector("#signature-container").style.transformOrigin = "0 0";
                    document.querySelector("#signature-container").style.marginLeft = "0px";
                } else { // 竖屏
                    this.entershuping = true;
                    document.getElementById("canvas").style.display = "none";
                    document.getElementById("canvas2").style.display = "block";
                    this.canvas = document.getElementById("canvas2");
                    this.ctx = this.canvas.getContext("2d");
                    this.canvas.height = window.innerHeight;
                    this.canvas.width = window.innerWidth - 40 - 40;
                    this.ctx.lineWidth = 1;
                    this.ctx.strokeStyle = "#000000";
                    this.drawEvent();
                    document.querySelector("#signature-container").style.width = window.innerHeight + "px";
                    document.querySelector("#signature-container").style.height = window.innerWidth + "px";
                    document.querySelector("#signature-container").style.transform = "rotate(90deg)";
                    document.querySelector("#signature-container").style.transformOrigin = "0 0";
                    document.querySelector("#signature-container").style.marginLeft = window.innerWidth + "px";
                }
            }
            
            // 绘画事件
            Signatrue.prototype.drawEvent = function() {
                var self = this;
                this.canvas.addEventListener("touchstart", function(evt) {
                    var oEvent = evt || event;
                    oEvent.preventDefault();
                    var position = self.pos(oEvent);
                    self.ctx.beginPath();
                    self.ctx.moveTo(position.x, position.y);
                    if (self.firstTouch) {
                        self.minparams = {
                            x: position.x,
                            y: position.y
                        };
                        self.maxparams = {
                            x: position.x,
                            y: position.y
                        };
                        self.firstTouch = false;
                    } else {
                        self.judgeSize(position);
                    }
                    self.canvas.addEventListener("touchmove", touchmove, false)
                
                    function touchmove(evt) {
                        var oEvent = evt || event;
                        oEvent.preventDefault();
                        var position = self.pos(oEvent);
                        self.ctx.lineTo(position.x, position.y);
                        self.judgeSize(position);
                        self.ctx.stroke();
                    }
                    document.addEventListener("touchend", touchend, false)
                
                    function touchend(evt) {
                        var oEvent = evt || event;
                        oEvent.preventDefault();
                        self.allowSubmit = true;
                        self.canvas.removeEventListener("touchmove", touchmove);
                        document.removeEventListener("touchend", touchend);
                    }
                })
            }
            
            // 清空画笔
            Signatrue.prototype.clear = function() {
                var self = this;
                document.getElementById("clean_canvas").addEventListener("click", function() {
                    self.ctx.clearRect(0, 0, self.canvas.width, self.canvas.height);
                    self.allowSubmit = false;
                })
            }
            
            // 提交画笔内容
            Signatrue.prototype.submit = function() {
                var self = this;
                document.getElementById("sure_canvas").addEventListener("click", function() {
                    if (self.allowSubmit) {
                        var imgSRC = self.canvas.toDataURL('image/png', 1);
                        var img = new Image();
                        img.src = imgSRC;
                        self.ctx.clearRect(0, 0, self.canvas.width, self.canvas.height);
                        img.onload = function() {
                            var width = self.maxparams.x - self.minparams.x;
                            var height = self.maxparams.y - self.minparams.y;
                            var targetWidth = 200;
                            var targetHeight = 100;
                            var clipCanvas = document.createElement("canvas");
                            clipCanvas.width = targetWidth;
                            clipCanvas.height = targetHeight;
                            var ctx2 = clipCanvas.getContext("2d");
                            if (self.entershuping) {
                                ctx2.translate(0, targetHeight);
                                ctx2.rotate(-90 * Math.PI / 180);
                                ctx2.drawImage(img, self.minparams.x, self.minparams.y, width, height, 0, 0, targetHeight, targetWidth);
                            } else {
                                ctx2.drawImage(img, self.minparams.x, self.minparams.y, width, height, 0, 0, targetWidth, targetHeight);
                            }
                            var imgSRC2 = clipCanvas.toDataURL('image/png', 1);
                            if(self.options && self.options.callback && typeof self.options.callback == 'function') {
                                self.options.callback(imgSRC2);
                            }
                            self.canvas = null;
                            self.ctx = null;
                            ctx2 = null;
                            clipCanvas = null;
                            
                        }
                    } else {
                        alert("没有手写签名，不能提交!")
                    }
                })
            }
            
            
            // 获取当前位置
            Signatrue.prototype.pos = function(event) {
                var x = event.touches[0].pageX - event.target.offsetLeft;
                var y = event.touches[0].pageY - event.target.offsetTop;
                return {
                    x: x,
                    y: y
                };
            }
            
            // 优化画笔界限，去掉空白区域
            Signatrue.prototype.judgeSize = function(value) {
                if (this.minparams.x > value.x) {
                    this.minparams.x = value.x;
                }
                if (this.maxparams.x < value.x) {
                    this.maxparams.x = value.x;
                }
                if (this.minparams.y > value.y) {
                    this.minparams.y = value.y;
                }
                if (this.maxparams.y < value.y) {
                    this.maxparams.y = value.y;
                }
            }
            
            return Signatrue;
        })();
        
        
        // 点击去手写签名-展示手写签名弹框
        document.getElementById('signature-button').addEventListener('click',function(){
            document.getElementById('signature-pop').style.display = 'block';
            var signatrueDraw = new SignatureClass({
                callback: function(base64) {
                    document.getElementById('signature-img').src = base64;
                    document.getElementById('signature-pop').style.display = 'none';
                    document.getElementById('signature-img').style.display = 'block';
                }
            });
            signatrueDraw.init();

        },false);
        
        // 点击弹框返回
        document.getElementById('return').addEventListener('click',function(){
            document.getElementById('signature-pop').style.display = 'none';
        },false);
    </script>
</html>
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  • 原文地址：https://www.cnblogs.com/moqiutao/p/14439314.html
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