我有多个画布，这些画布用作图层。
canvas c1 = background image. canvas c2 = charactor image. canvas c3 = item image.
我的源代码如下。
在同一位置设置三个画布。
<div canvas="canvas-wrap">
<canvas class="canvas" id="c1">
<canvas class="canvas" id="c2">
<canvas class="canvas" id="c3">
</div>
.canvas-wrap{
width: 600px;
height:500px;
max-width: 100%;
position: relative;
padding: 0;
box-sizing: content-box;
}
.canvas{
position: absolute;
left:0;
top:0;
border: 0;
max-width:100%;
box-sizing: content-box;
padding: 0;
margin: 0;
}
现在，我想将这些画布导出为一张 jpg。
我有可以导出一张画布的源代码，但我想从三张画布中导出一张jpg。
function saveCanvas(canvas_id)
{
var canvas = document.getElementById("c1");
var a = document.createElement('a');
a.href = canvas.toDataURL('image/jpeg', 0.85);
a.download = 'download.jpg';
a.click();
} 
这是可能的，但更好的方法是使用 1 个画布并将所有内容绘制到那里。
在这里，我们创建一个虚拟画布，循环遍历所有画布以将数据绘制到其上，然后保存该画布生成的图像。
//store all canvasses in array so we can loop through them later const canvasses = []; ['c1','c2','c3'].forEach(canvasId => { canvasses.push(document.getElementById(canvasId)); }); function save(){ //create one canvas to draw everything to const canvas = document.createElement("canvas"); canvas.width = canvasses[0].width; canvas.height = canvasses[0].height; //draw other canvases here const ctx = canvas.getContext('2d'); canvasses.forEach(data => { ctx.drawImage(data, 0, 0); }); //original saving code, using the fake canvas we created var a = document.createElement('a'); a.href = canvas.toDataURL('image/jpeg', 0.85); a.download = 'download.jpg'; a.click(); }