下载图片到本地

/**
 * 下载图片到本地
 * @param {String} domId img标签的id
 * @param {String} name  下载图片名称
 */
function downloadCanvasIamge(domId, name){
  let image = new Image()
  // 解决跨域 Canvas 污染问题
  image.setAttribute('crossOrigin', 'anonymous')
  image.onload = function () {
    let canvas = document.createElement('canvas')
    canvas.width = image.width
    canvas.height = image.height
    let context = canvas.getContext('2d')
    context.drawImage(image, 0, 0, image.width, image.height)
    let url = canvas.toDataURL('image/png')
    let a = document.createElement('a')
    let event = new MouseEvent('click')
    a.download = name || '下载图片'
    a.href = url
    a.dispatchEvent(event)
  }
  image.src = document.getElementById(domId).src
}