将页面中的canvas导出为图片

const canvasDom = this.$refs[canvas]; //获取canvas DOM对象
const imageData = canvasDom.toDataURL('image/png'); //返回base64的URL
const elink = document.createElement('a');
elink.download = '图片';
elink.style.display = 'none';
elink.href = imageData;
document.body.appendChild(elink);
elink.click();
URL.revokeObjectURL(elink.href); //释放URL对象
document.body.removeChild(elink);