信息: IE10 +完全不支持以下方法。其他人已经完成了工作并实现了跨浏览器解决方案。这就是其中之一。
首先,将生成的数据URL添加到标签的href
属性中<a>
。但是,在某些浏览器上,仅此一项就不会触发下载。相反,它将在新页面中打开链接的图像。
<img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUg...." class="image" />
根据以上示例,将数据URL的MIME类型转换为此:
<a href="data:application/octet-stream;base64,iVBORw0KGgoAAAANSUhEUg....">Download</a>
通过告诉浏览器数据是application/octet-stream
,它将要求您将数据保存在硬盘上。
A)download
Google Crome引入的属性
<a download="image.png" href="...">
B)在数据URL中定义HTTP标头headers=Content-Disposition: attachment; filename=image.png
<a href="data:application/octet-stream;headers=Content-Disposition%3A%20attachment%3B%20filename=image.png;base64,iVBORw0KGgoAAAA">
这至少在某些较旧的Opera版本中有效。这里是一些讨论。
对主要浏览器的Bug /功能跟踪系统的研究表明,定义文件名是社区的一个很大愿望。也许我们会在不久的将来看到跨浏览器兼容的解决方案!;)
如果您不想膨胀访问者的浏览器的RAM,还可以动态生成数据URL:
<a id="dl" download="Canvas.png">Download Canvas</a>
function dlCanvas() {
var dt = canvas.toDataURL('image/png');
this.href = dt;
};
dl.addEventListener('click', dlCanvas, false);
这样,您的画布仍可能被浏览器显示为图像文件。如果要增加打开下载对话框的可能性,则应扩展上述功能,以便它进行替换,如上所示:
function dlCanvas() {
var dt = canvas.toDataURL('image/png');
this.href = dt.replace(/^data:image\/[^;]/, 'data:application/octet-stream');
};
dl.addEventListener('click', dlCanvas, false);
最后,添加HTTP标头以确保大多数浏览器为您提供有效的文件名!;)
var canvas = document.getElementById("cnv");
var ctx = canvas.getContext("2d");
/* FILL CANVAS WITH IMAGE DATA */
function r(ctx, x, y, w, h, c) {
ctx.beginPath();
ctx.rect(x, y, w, h);
ctx.strokeStyle = c;
ctx.stroke();
}
r(ctx, 0, 0, 32, 32, "black");
r(ctx, 4, 4, 16, 16, "red");
r(ctx, 8, 8, 16, 16, "green");
r(ctx, 12, 12, 16, 16, "blue");
/* REGISTER DOWNLOAD HANDLER */
/* Only convert the canvas to Data URL when the user clicks.
This saves RAM and cpu ressources in case this feature is not required. */
function dlCanvas() {
var dt = canvas.toDataURL('image/png');
/* Change MIME type to trick the browser to downlaod the file instead of displaying it */
dt = dt.replace(/^data:image\/[^;]*/, 'data:application/octet-stream');
/* In addition to <a>'s "download" attribute, you can define HTTP-style headers */
dt = dt.replace(/^data:application\/octet-stream/, 'data:application/octet-stream;headers=Content-Disposition%3A%20attachment%3B%20filename=Canvas.png');
this.href = dt;
};
document.getElementById("dl").addEventListener('click', dlCanvas, false);
<canvas id="cnv" width="32" height="32"></canvas>
<a id="dl" download="Canvas.png" href="#">Download Canvas</a>