js图片下载方式

/**
 * 创建 <a> 标签下载文件流格式图片
 * @param file 
 * @param fileName 
 */
export const downloadFile = (file: string, fileName?: string) => {
  const blob = new Blob([file]);
  const fileReader = new FileReader();
  fileReader.readAsDataURL(blob);
  fileReader.onload = (e) => {
    const a = document.createElement("a");
    a.download = fileName || '0123456.PNG';
    a.href = e.target?.result as string;
    document.body.appendChild(a);
    a.click();
    document.body.removeChild(a);
  };
}

export const downloadFileUrl = (file: Blob) => {
  const blob = new Blob([file]);
  const fileReader = new FileReader();
  fileReader.readAsDataURL(blob);
  fileReader.onload = (e) => {
    const url = e.target?.result as string;
    downloadImage(`data:image/png;Base64,${url}`, 'testefd')
  };
}

/**
 * 根据图片路径下载
 * @param imgsrc 图片路径
 * @param name 下载图片名称
 * @param type 格式图片，可选，默认png ，可选 png/jpeg
 */
export const downloadImage = (imgsrc: string, name: string, type: string = 'png') => {
  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/${type}`); //得到图片的base64编码数据
    let a = document.createElement("a"); // 生成一个a元素
    let event = new MouseEvent("click"); // 创建一个单击事件
    a.download = name || "pic"; // 设置图片名称
    a.href = url; // 将生成的URL设置为a.href属性
    a.dispatchEvent(event); // 触发a的单击事件
  }
  //将资源链接赋值过去，才能触发image.onload 事件
  image.src = imgsrc
}