浏览器/ HTML强制从src =“ data：image / jpeg; base64…”下载图像

我在客户端生成图像，并使用HTML显示如下：

<img src="data:image/jpeg;base64,/9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAAMCAgICAgM...."/>

我想提供下载生成的图像的可能性。

我怎么能知道浏览器正在打开文件保存对话框（或者只是将chrome或firefox这样的图像下载到下载文件夹即可），从而允许用户保存图像而无需右键单击并另存为图像？

我希望没有服务器交互的解决方案。因此，我知道如果我先上传图像然后开始下载，那将是可能的。

非常感谢！

只需替换image/jpeg为application/octet-stream。客户端不会将URL识别为可内联资源，并提示下载对话框。

一个简单的JavaScript解决方案是：

//var img = reference to image
var url = img.src.replace(/^data:image\/[^;]+/, 'data:application/octet-stream');
window.open(url);
// Or perhaps: location.href = url;
// Or even setting the location of an <iframe> element, 

另一种方法是使用blob:URI：

var img = document.images[0];
img.onclick = function() {
    // atob to base64_decode the data-URI
    var image_data = atob(img.src.split(',')[1]);
    // Use typed arrays to convert the binary data to a Blob
    var arraybuffer = new ArrayBuffer(image_data.length);
    var view = new Uint8Array(arraybuffer);
    for (var i=0; i<image_data.length; i++) {
        view[i] = image_data.charCodeAt(i) & 0xff;
    }
    try {
        // This is the recommended method:
        var blob = new Blob([arraybuffer], {type: 'application/octet-stream'});
    } catch (e) {
        // The BlobBuilder API has been deprecated in favour of Blob, but older
        // browsers don't know about the Blob constructor
        // IE10 also supports BlobBuilder, but since the `Blob` constructor
        //  also works, there's no need to add `MSBlobBuilder`.
        var bb = new (window.WebKitBlobBuilder || window.MozBlobBuilder);
        bb.append(arraybuffer);
        var blob = bb.getBlob('application/octet-stream'); // <-- Here's the Blob
    }

    // Use the URL object to create a temporary URL
    var url = (window.webkitURL || window.URL).createObjectURL(blob);
    location.href = url; // <-- Download!
};

Relevant documentation

• atob
• Typed arrays
• URL.createObjectURL
• Blob and BlobBuilder

you can use the download attribute on an a tag ...

<a href="data:image/jpeg;base64,/9j/4AAQSkZ..." download="filename.jpg"></a>

see more: https://developer.mozilla.org/en/HTML/element/a#attr-download

I guess an img tag is needed as a child of an a tag, the following way:

<a download="YourFileName.jpeg" href="data:image/jpeg;base64,iVBO...CYII=">
    <img src="data:image/jpeg;base64,iVBO...CYII="></img>
</a>

or

<a download="YourFileName.jpeg" href="/path/to/OtherFile.jpg">
    <img src="/path/to/OtherFile.jpg"></img>
</a>

Only using the a tag as explained in #15 didn't worked for me with the latest version of Firefox and Chrome, but putting the same image data in both a.href and img.src tags worked for me.

From JavaScript it could be generated like this:

var data = canvas.toDataURL("image/jpeg");

var img = document.createElement('img');
img.src = data;

var a = document.createElement('a');
a.setAttribute("download", "YourFileName.jpeg");
a.setAttribute("href", data);
a.appendChild(img);

var w = open();
w.document.title = 'Export Image';
w.document.body.innerHTML = 'Left-click on the image to save it.';
w.document.body.appendChild(a);

Take a look at FileSaver.js. It provides a handy saveAs function which takes care of most browser specific quirks.