<canvas id="canvas" width="400" height="400"></canvas>
<div><button id="save">保存</button>
</div>

var arr = [{locations:[[0,0],[200,200],[0,400]],color:"red"},{locations:[[0,0],[400,0],[200,200]],color:"orange"},{locations:[[0,400],[100,300],[200,400]],color:"yellow"},{locations:[[100,300],[200,200],[300,300],[200,400]],color:"green"},{locations:[[300,100],[200,200],[300,300]],color:"blue"},{locations:[[300,100],[400,0],[400,200],[300,300]],color:"indigo"},{locations:[[200,400],[400,400],[400,200]],color:"purple"}
];
var oCanvas = document.getElementById("canvas");
var ctx = oCanvas.getContext("2d");
for(let i=0;i<arr.length;i  ){draw(arr[i],ctx);
}function draw(item,ctx){ctx.beginPath();ctx.moveTo(item.locations[0][0],item.locations[0][1]);for(let i = 0;i<item.locations.length;i  ){let x = item.locations[i][0];let y = item.locations[i][1];ctx.lineTo(x,y);console.log(1234567)}ctx.closePath();ctx.fillStyle = item.color;ctx.fill();ctx.strokeStyle = "#000";ctx.lineWidth = 2;ctx.stroke();
}
var imgId = document.getElementById("imgId");
document.getElementById("save").onclick = function (){downLoad(saveAsPNG(canvas));
}// 保存成png格式的图片
function saveAsPNG(canvas) {return canvas.toDataURL("image/png");
}// 保存成jpg格式的图片
function saveAsJPG(canvas) {return canvas.toDataURL("image/jpeg");
}// 保存成bmp格式的图片  目前浏览器支持性不好
function saveAsBMP(canvas) {return canvas.toDataURL("image/bmp");
}/*** @author web得胜* @param {String} url 需要下载的文件地址* */
function downLoad(url){var oA = document.createElement("a");oA.download = '';// 设置下载的文件名，默认是'下载'oA.href = url;document.body.appendChild(oA);oA.click();oA.remove(); // 下载之后把创建的元素删除
}