Javascript 如何将画布保存为png图像？

how to save canvas as png image?

提问by sneaky

I have a canvas element with a drawing in it, and I want to create a button that when clicked on, it will save the image as a png file. So it should open up the save, open, close dialog box...

我有一个带有绘图的画布元素，我想创建一个按钮，单击该按钮时，它将图像保存为 png 文件。所以它应该打开保存，打开，关闭对话框......

I do it using this code

我使用此代码执行此操作

var canvas = document.getElementById("myCanvas");
window.open(canvas.toDataURL("image/png"));

But when I test it out in IE9, a new window opens up saying "the web page cannot be displayed" and the url of it is:

但是当我在 IE9 中测试它时，会打开一个新窗口，说“无法显示网页”，它的 url 是：

data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAmAAAABpCAYAAACd+58xAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAADRwSURBVHhe7V0HgBVF0q7ZJSlJwRxAPUFRD39RFLN34qGnnomoqIjhzBlFPROIgsoZzogR5AQEzJ4BPFAUEUwgJjgQkCQKooggaf/6el6/6ZnpSW/zUn237u5MdXX1172+z6rqaqeEG6VsJet+pDW/vkdrfx3H3yfT2tVzaP26X6hkw1q/BoeI/280/29JwznZxJPUyXtBQBAQBAQBQaBcECjefmi56BWlZYtAeqajx/WokfrJYEqOIikOFRfXoVq161PtOk2odu0t+ectqKiojnrntWhC46QhYOtXfUarl79Ivy9/ldau+h+tX/8b2SbjJ07pWFQy2Uqnp2yXSrQJAoKAICAICALJCAgBS8ao8iTi/UvpSZlBxiwqwWOKimsxCWtEdettR3XqbEfFtRonkrBYArZh3fe0+senadWyEbRm1UzasP53K45ZiFc84RKyVXkbVUYWBAQBQUAQyIqAELCsiFW2fDQpSyZk8UQMMysqKmaPWCOqt8mOVK/eTuQU1YuccCQBW7dyIq38/j5a/fN/ad3a5QGXmqsvLfGKJl0ZCFdONEOPyl5lGV8QEAQEAUGghiMgBKzqLHCeHqVOrILtduF4MpZExEqoVq167A3bmjap34J/bmoFqcj2dM3Pr9GK+b1p5bJXmXz9nEC+3FiorYF4hcmXlo+gUrk+um/+e+QoVWfxxRJBQBAQBAQBQUAQqBwE8uzCwiMiaEqOWYR5jJ2/6Hl58nYHk0Pr1v1Ov62cTytXfE5r1yyyc6RgDhjI16+L+tLqFZ9xnteGUKc0Xi876YpYkFDCfpqFEz9YGpRERhAQBAQBQaB8ERAPWPnim157JreX6/eK7eJ/Ge0RS8oPc9gT1pTqN2jFocltfdPxecBU2HHxgBTky+71CjPGCO+YyU4j0TU9ZcGf0y+JSAoCgoAgIAgIAoJATUcgG2dQ0jpKZ/Xp+PlLtEcs3huGQhO/r17K3rBvuGrEUt8i5HPAkHC/Yt6lKuwYKiuRM9TtGbY0rcerTBLwC/KY1fSNJ/MTBAQBQUAQqAwExANWGaiHx0z2aJl9CknET+MRc2XsVSKKaNP6O1CDhvtwYn5dJZf3gOG0IxLuS0e+LB4vw9sVhiwmHywmF6xqLLdYIQgIAoKAICAICAJVAQHTo2XmkNtzv6K5R7RXLOwRs3MaW+47SNkG9oRxZQmun6qbImCo84VSE+5pR3/zvFZJni/7e8tTHiCeqCkAqsKKig2CgCAgCAgCgoAgUG0RCBKzMLmwkzHdL4pk4XlUAn7Uu3XrVtPqVfO4lurPSq0KQa5cdAv9snBgqM5XFPlKSsSPM8o3mcxES2hZtf0rEMMFAUFAEKiBCEgIsqotavpk/OiwZViHPQk/LgHfHo5EnbCGjVpxeYo9yNmw9oeSn2YeTatWTPNzozzX8ZOeWPJlJVRJnrOoxUtJtmLEUmqoartH7BEEBAFBQBCoJggIASu/hUqkUokC2rZkwSSCBU12wpadhNXbpAk13vwwKlJ3O/L1QmYrxPNlDxuGyVtyIn6K8KSZHwY3XsRX+W0L0VyTEPjwM6KuFxN1uiB6Vkv48MpdjxLt9ieieQvscuvWE13eh2jnQ9zv+F2aICAICAKCQGEIRH22559H5IqnDTMGeU/SgUJ7WNLjOVH9g8/Xrv2Fa4P9SM6K7y4t+WXRw76sfVc42fPV936iJ5+LKrbqTU0P3rA+0dZbEh20L9HJHYj23I2oVrHFT5U5NFnY4m6svUA0Pvo8efbvjCBqtr0nN+IVot4Dkvv1v5aoy/HJcpUpsfI3olffdknV0uWuJfv9kWjkw55VIFAfM073PE4EkqZbEBf9HMTs8C6e3KhHiPbdqzJnKWMLAoJAeSMgHrDyRrj0+rOEGvVoYY9Y0inIeE+YqQ+cqGGj3dgDtvJjC/mKm7BHmG68lGjO+0T

数据：图像/png；base64，iVBORw0KGgoAAAANSUhEUgAAAmAAAABpCAYAAACd + 58xAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAADRwSURBVHhe7V0HgBVF0q7ZJSlJwRxAPUFRD39RFLN34qGnnomoqIjhzBlFPROIgsoZzogR5AQEzJ4BPFAUEUwgJjgQkCQKooggaf / 6el6 / 6ZnpSW / zUn237u5MdXX1172 + z6rqaqeEG6VsJet + PDW / vkdrfx3H3yfT2tVzaP26X6hkw1q / BoeI / 280 / 29JwznZxJPUyXtBQBAQBAQBQaBcECjefmi56BWlZYtAeqajx / WokfrJYEqOIikOFRfXoVq161PtOk2odu0t + ectqKiojnrntWhC46QhYOtXfUarl79Ivy9 / ldau + H + TX / 8b2SbjJ07pWFQy2Uqnp2yXSrQJAoKAICAICALJCAgBS8ao8iTi / UvpSZlBxiwqwWOKimsxCWtEdettR3XqbEfFtRonkrBYArZh3fe0 + senadWyEbRm1UzasP53K45ZiFc84RKyVXkbVUYWBAQBQUAQyIqAELCsiFW2fDQpSyZk8UQMMysqKmaPWCOqt8mOVK / eTuQU1YuccCQBW7dyIq38 / J5A / fN的/ ad3a5QGXmqsvLfGKJl0ZCFdONEOPyl5lGV8QEAQEAUGghiMgBKzqLHCeHqVOrILtduF4MpZExEqoVq167A3bmjap34J / bmoFqcj2dM3Pr9GK + b1p5bJXmXz9nEC + 3FiorYF4hcmXlo+gUrk+um/+e+QoVWfxxRJBQBAQBAQBQUAQqBwE8uzCwiMiaEqOWYR5jJ2/6Hl58nYHk0Pr1v1Ov62cTytXfE5r1yyyc6RgDhjI16 + L + tLqFZ9xnteGUKc0Xi876YpYkFDCfpqFEz9YGpRERhAQBAQBQaB8ERAPWPnim157JreX6 / eK7eJ / Ge0RS8oPc9gT1pTqN2jFocltfdPxecBU2HHxgBTky + 71CjPGCO + YyU4j0TU9ZcGf0y + JSAoCgoAgIAgIAoJATUcgG2dQ0jpKZ / XP + PlLtEcs3huGQhO / r17K3rBvuGrEUt8i5HPAkHC / Yt6lKuwYKiuRM9TtGbY0rcerTBLwC / KY1fSNJ / MTBAQBQUAQqAwExANWGaiHx0z2aJl9CknET + MRc2XsVSKKaNP6O1CDhvtwYn5dJZf3gOG0IxLuS0e + LB4vw9sVhiwmHywmF6xqLLdYIQgIAoKAICAICAJVAQHTo2XmkNtzv6K5R7RXLOwRs3MaW + 47SNkG9oRxZQmun6qbImCo84VSE + 5pR3 / zvFZJni / 7e8tTHiCeqCkAqsKKig2CgCAgCAgCgoAgUG0RCBKzMLmwkzHdL4pk4XlUAn7Uu3XrVtPqVfO4lurPSq0KQa5cdAv9snBgqM5XFPlKSsSPM8o3mcxES2hZtf0rEMMFAUFAEKiBCEgIsqotavpk / OiwZViHPQk / LgHfHo5EnbCGjVpxeYo9yNmw9oeSn2YeTatWTPNzozzX8ZOeWPJlJVRJnrOoxUtJtmLEUmqoartH7BEEBAFBQBCoJggIASu / hUqkUokC2rZkwSSCBU12wpadhNXbpAk13vwwKlJ3O / L1QmYrxPNlDxuGyVtyIn6K8KSZHwY3XsRX + W0L0VyTEPjwM6KuFxN1uiB6Vkv48MpdjxLt9ieieQvscuvWE13eh2jnQ9zv + F2aICAICAKCQGEIRH22559H5IqnDTMGeU / SgUJ7WNLjOVH9g8 / Xrv2Fa4P9SM6K7y4t + WXRw76sfVc42fPV936iJ5 + LKrbqTU0P3rA + 0dZbEh20L9HJHYj23I2oVrHFT5U5NFnY4m6svUA0Pvo8efbvjCBqtr0nN + IVot4Dkvv1v5aoy / HJcpUpsfI3olffdknV0uWuJfv9kWjkw55VIFAfM073PE4EkqZbEBf9HMTs8C6e3KhHiPbdqzJnKWMLAoJAeSMgHrDyRrj0 + rOEGvVoYY9Y0inIeE + YQQ + cqGGj3dgDtvJjC / mKm7BHmG68lGjO + 0T

Anyone know how to fix this?

有人知道怎么修这个东西吗？

回答by TheVillageIdiot

try this:

尝试这个：

var c=document.getElementById("alpha");
var d=c.toDataURL("image/png");
var w=window.open('about:blank','image from canvas');
w.document.write("<img src='"+d+"' alt='from canvas'/>");

This shows image from canvas on new page, but if you have open popup in new tabsetting it shows about:blankin address bar.

这会在新页面上显示画布中的图像，但如果您进行了open popup in new tab设置，它会显示about:blank在地址栏中。

EDIT:- though window.open("<img src='"+ c.toDataURL('image/png') +"'/>")does not work in FF or Chrome, following works though rendering is somewhat different from what is shown on canvas, I think transparency is the issue:

编辑：-虽然window.open("<img src='"+ c.toDataURL('image/png') +"'/>")在 FF 或 Chrome 中不起作用，但后续工作虽然渲染与画布上显示的有所不同，但我认为透明度是问题：

window.open(c.toDataURL('image/png'));

回答by Maurice

FileSaver.jsshould be able to help you here.

FileSaver.js应该能够帮助你。

var canvas = document.getElementById("my-canvas");
// draw to canvas...
canvas.toBlob(function(blob) {
    saveAs(blob, "pretty image.png");
});

回答by Tovask

I used this solution to set the file name:

我使用此解决方案来设置文件名：

HTML:

HTML：

<a href="#" id="downloader" onclick="download()" download="image.png">Download!</a>
<canvas id="canvas"></canvas>

JavaScript:

JavaScript：

function download(){
    document.getElementById("downloader").download = "image.png";
    document.getElementById("downloader").href = document.getElementById("canvas").toDataURL("image/png").replace(/^data:image\/[^;]/, 'data:application/octet-stream');
}

回答by Plcode

I had this problem and this is the best solution without any external or additional script libraries: In Javascript tags or file create this function: We assume here that canvas is your canvas:

我遇到了这个问题，这是最好的解决方案，没有任何外部或额外的脚本库：在 Javascript 标签或文件中创建这个函数：我们在这里假设画布是你的画布：

function download(){
        var download = document.getElementById("download");
        var image = document.getElementById("canvas").toDataURL("image/png")
                    .replace("image/png", "image/octet-stream");
        download.setAttribute("href", image);

    }

In the body part of your HTML specify the button:

在 HTML 的正文部分指定按钮：

<a id="download" download="image.png"><button type="button" onClick="download()">Download</button></a>

This is working and download link looks like a button. Tested in Firefox and Chrome.

这是有效的，下载链接看起来像一个按钮。在 Firefox 和 Chrome 中测试。

回答by Bill Bronson

I maybe discovered a better way for not forcing the user to right click and "save image as". Live draw the canvas base64 code into the hrefof the link and modify it so the download will start automatically. I don't know if it's universally browser compatible, but it should work with the main/new browsers.

我可能发现了一种更好的方法来不强迫用户右键单击并“将图像另存为”。将画布 base64 代码实时绘制到href链接中并进行修改，以便自动开始下载。我不知道它是否普遍兼容浏览器，但它应该适用于主要/新浏览器。

var canvas = document.getElementById('your-canvas');
    if (canvas.getContext) {
        var C = canvas.getContext('2d');
    }

$('#your-canvas').mousedown(function(event) {
    // feel free to choose your event ;) 

    // just for example
    // var OFFSET = $(this).offset();
    // var x = event.pageX - OFFSET.left;
    // var y = event.pageY - OFFSET.top;

    // standard data to url
    var imgdata = canvas.toDataURL('image/png');
    // modify the dataUrl so the browser starts downloading it instead of just showing it
    var newdata = imgdata.replace(/^data:image\/png/,'data:application/octet-stream');
    // give the link the values it needs
    $('a.linkwithnewattr').attr('download','your_pic_name.png').attr('href',newdata);

});

You can wrap the <a>around anything you want.

你可以环绕<a>任何你想要的东西。

回答by noontz

To accomodate all three points:

为了满足所有三点：

• button
• save the image as a png file
• open up the save, open, close dialog box

• 按钮
• 将图像保存为 png 文件
• 打开保存、打开、关闭对话框

The file dialog is a setting in the browser.

文件对话框是浏览器中的一个设置。

For the button/save part assign the following function, boiled down from other answers, to your buttons onclick:

对于按钮/保存部分，将从其他答案归结为以下功能分配给您的按钮 onclick：

function DownloadCanvasAsImage(){
    let downloadLink = document.createElement('a');
    downloadLink.setAttribute('download', 'CanvasAsImage.png');
    let canvas = document.getElementById('myCanvas');
    let dataURL = canvas.toDataURL('image/png');
    let url = dataURL.replace(/^data:image\/png/,'data:application/octet-stream');
    downloadLink.setAttribute('href', url);
    downloadLink.click();
}

Example on Codepen

Codepen 上的示例

Another, somewhat cleaner, approach is using Canvas.toBlob():

另一种更简洁的方法是使用Canvas.toBlob()：

function DownloadCanvasAsImage(){
    let downloadLink = document.createElement('a');
    downloadLink.setAttribute('download', 'CanvasAsImage.png');
    let canvas = document.getElementById('myCanvas');
    canvas.toBlob(function(blob) {
      let url = URL.createObjectURL(blob);
      downloadLink.setAttribute('href', url);
      downloadLink.click();
    });
}

Example on Codepen

Codepen 上的示例

Neither solution is 100% cross browser compatible, so check the client

这两种解决方案都不是 100% 跨浏览器兼容的，因此请检查客户端

回答by J.M.I. MADISON

Full Working HTML Code. Cut+Paste into new .HTML file:

完整的工作 HTML 代码。剪切+粘贴到新的 .HTML 文件中：

Contains Two Examples:

包含两个例子：

1. Canvas in HTML file.
2. Canvas dynamically created with Javascript.

1. HTML 文件中的画布。
2. 使用 Javascript 动态创建的画布。

Tested In:

测试：

1. Chrome
2. Internet Explorer
3. *Edge (title name does not show up)
4. Firefox
5. Opera

1. 铬合金
2. IE浏览器
3. *Edge（标题名称不显示）
4. 火狐
5. 歌剧

---

---

<!DOCTYPE HTML >
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title> #SAVE_CANVAS_TEST# </title>
    <meta 
        name   ="author" 
        content="John Mark Isaac Madison"
    >
    <!-- EMAIL: J4M4I5M7 -[ＡＴ]- Hotmail.com -->
</head>
<body>

<div id="about_the_code">
    Illustrates:
    <ol>
    <li>How to save a canvas from HTML page.     </li>
    <li>How to save a dynamically created canvas.</li>
    </ol>
</div>

<canvas id="DOM_CANVAS" 
        width ="300" 
        height="300"
></canvas>

<div id="controls">
    <button type="button" style="width:300px;"
            onclick="obj.SAVE_CANVAS()">
        SAVE_CANVAS ( Dynamically Made Canvas )
    </button>

    <button type="button" style="width:300px;"
            onclick="obj.SAVE_CANVAS('DOM_CANVAS')">
        SAVE_CANVAS ( Canvas In HTML Code )
    </button>
</div>

<script>
var obj = new MyTestCodeClass();
function MyTestCodeClass(){

    //Publically exposed functions:
    this.SAVE_CANVAS = SAVE_CANVAS;

    //:Private:
    var _canvas;
    var _canvas_id = "ID_OF_DYNAMIC_CANVAS";
    var _name_hash_counter = 0;

    //:Create Canvas:
    (function _constructor(){
        var D   = document;
        var CE  = D.createElement.bind(D);
        _canvas = CE("canvas");
        _canvas.width = 300;
        _canvas.height= 300;
        _canvas.id    = _canvas_id;
    })();

    //:Before saving the canvas, fill it so
    //:we can see it. For demonstration of code.
    function _fillCanvas(input_canvas, r,g,b){
        var ctx = input_canvas.getContext("2d");
        var c   = input_canvas;

        ctx.fillStyle = "rgb("+r+","+g+","+b+")";
        ctx.fillRect(0, 0, c.width, c.height);
    }

    //:Saves canvas. If optional_id supplied,
    //:will save canvas off the DOM. If not,
    //:will save the dynamically created canvas.
    function SAVE_CANVAS(optional_id){

        var c = _getCanvas( optional_id );

        //:Debug Code: Color canvas from DOM
        //:green, internal canvas red.
        if( optional_id ){
            _fillCanvas(c,0,255,0);
        }else{
            _fillCanvas(c,255,0,0);
        }

        _saveCanvas( c );
    }

    //:If optional_id supplied, get canvas
    //:from DOM. Else, get internal dynamically
    //:created canvas.
    function _getCanvas( optional_id ){
        var c = null; //:canvas.
        if( typeof optional_id == "string"){
            var id = optional_id;
            var  d = document;
            var c  = d.getElementById( id );
        }else{
            c = _canvas; 
        }
        return c;
    }

    function _saveCanvas( canvas ){
        if(!window){ alert("[WINDOW_IS_NULL]"); }

        //:We want to give the window a unique
        //:name so that we can save multiple times
        //:without having to close previous
        //:windows.
        _name_hash_counter++              ; 
        var NHC = _name_hash_counter      ;
        var URL = 'about:blank'           ;
        var name= 'UNIQUE_WINDOW_ID' + NHC;
        var w=window.open( URL, name )    ;

        if(!w){ alert("[W_IS_NULL]");}

        //:Create the page contents,
        //:THEN set the tile. Order Matters.
        var DW = ""                        ;
        DW += "<img src='"                 ;
        DW += canvas.toDataURL("image/png");
        DW += "' alt='from canvas'/>"      ;
        w.document.write(DW)               ;
        w.document.title = "NHC"+NHC       ;

    }

}//:end class

</script>

</body>
<!-- In IE: Script cannot be outside of body.  -->
</html>

回答by Kehinde Omotoso

Submit a form that contains an input with value of canvas toDataURL('image/png') e.g

提交一个表单，其中包含一个值为 canvas toDataURL('image/png') 的输入，例如

//JAVASCRIPT

//Java脚本

    var canvas = document.getElementById("canvas");
    var url = canvas.toDataUrl('image/png');

Insert the value of the url to your hidden input on form element.

将 url 的值插入到表单元素上的隐藏输入中。

//PHP

//PHP

    $data = $_POST['photo'];
    $data = str_replace('data:image/png;base64,', '', $data);
    $data = base64_decode($data);
    file_put_contents("i".  rand(0, 50).".png", $data);

回答by chintan kotadiya

Try this:

尝试这个：

jQuery('body').after('<a id="Download" target="_blank">Click Here</a>');

var canvas = document.getElementById('canvasID');
var ctx = canvas.getContext('2d');

document.getElementById('Download').addEventListener('click', function() {
    downloadCanvas(this, 'canvas', 'test.png');
}, false);

function downloadCanvas(link, canvasId, filename) {
    link.href = document.getElementById(canvasId).toDataURL();
    link.Download = filename;
}

You can just put this code in console in firefox or chrom and after changed your canvas tag ID in this above script and run this script in console.

您可以将此代码放在 firefox 或 chrom 的控制台中，然后在上面的脚本中更改画布标签 ID 并在控制台中运行此脚本。

After the execute this code you will see the link as text "click here" at bottom of the html page. click on this link and open the canvas drawing as a PNG image in new window save the image.

执行此代码后，您将在 html 页面底部看到链接为文本“单击此处”。单击此链接并在新窗口中以 PNG 图像的形式打开画布绘图并保存图像。

回答by V? Duy Thành

var canvasId = chart.id + '-canvas';
var canvasDownloadId = chart.id + '-download-canvas';
var canvasHtml = Ext.String.format('<canvas id="{0}" width="{1}" height="{2}"></canvas><a id="{3}"/>',
canvasId,
chart.getWidth(),
chart.getHeight(),
canvasDownloadId);
var canvasElement = reportBuilder.add({ html: canvasHtml });

var canvas = document.getElementById(canvasId);

var canvasDownload = document.getElementById(canvasDownloadId);
canvasDownload.href = chart.getImage().data;
canvasDownload.download = 'chart';

canvasDownload.click();