多图下载并打包压缩

原文

1、jszip.js 压缩并保存图片
2、FileSaver.js 保存压缩文件

/**
 * 将图片转换成base64 并返回路径
 * @param img
 * @param {number} width 调用时传入具体像素值，控制大小 ,不传则默认图像大小
 * @param {number} height
 * @returns {string}
 */
function getBase64Image(img,width = 0,height = 0) {
  const canvas = document.createElement('canvas');
  canvas.width = width ? width : img.width;
  canvas.height = height ? height : img.height;
  const ctx = canvas.getContext('2d');
  ctx.drawImage(img, 0, 0, canvas.width, canvas.height);
  const dataURL = canvas.toDataURL();
  return dataURL;
}
/**
 * 检查是不是Base64
 * @param img
 * @returns {boolean}
 */
function IsBase64(img) {
  // jpg jpeg png gif
  const _img = img.toLowerCase();
  if (_img.endsWith('jpg') || _img.endsWith('jpeg') || _img.endsWith('png') || _img.endsWith('gif') )  return false;
  return true;
}
/**
 * 加载图片 加载成功后经图片返回
 * @param img
 * @returns {Promise<any>}
 */
function getBase64(img){
  let url: string;
  if (IsBase64(img)) {
    // 有一些数据 后台没有返回前缀
    const _base64 = 'data:image/jpeg;base64,';
    if (img.startsWith(_base64)) {
      url = img;
    } else {
      url = _base64 + img;
    }
    return url;
  } else {
    url = img;
    const image = new Image();
    image.crossOrigin = '*';
    image.src = url;
    return new Promise(function (resolve, reject) {
      image.onload =function (){
        resolve(getBase64Image(image));//将base64传给done上传处理
      }
    });
  }
}
/**
 * 压缩图片
 */
function setBase64Img(zip, imgFolder, base64, imgArr, index, downloadName) {
  base64 = base64.split('base64,')[1];
  imgFolder.file(downloadName + '_' + index + '.png', base64, { base64: true });
  if (index === imgArr.length - 1) {
    zip.generateAsync({ type: 'blob' }).then((blob) => {
      saveAs(blob, downloadName + '.zip');
    });
  }
}
/**
 * 下载压缩图片
 * @param {any[]} imgArr  图片合集
 * @param {string} imgKey  如果不是单纯的图片路径 需要传入路径的key
 */
export function downloadZipImage (imgArr: any[], imgKey = '', downloadName = 'img') {
  if (!imgArr || !imgArr.length) {
    return;
  }
  const zip = new JSZip();
  // 创建images文件夹
  const imgFolder = zip.folder('images');
  // test
  // imgArr = ['assets/img/charts/return-upper-level.png',
  // 'assets/img/tree/arrow_right.png',
  // 'assets/img/tree/arrow_left.png',
  // 'assets/img/charts/map_ShadowMap.png'];
  let index = 0; //  判断加载了几张图片的标识
  for (let i = 0;i < imgArr.length;i++) {
    const itemImg = imgKey ? imgArr[i][imgKey] : imgArr[i];
    /**
     * 如果是Base64就不需要再做异步处理了
     */
    const Base64Img = getBase64(itemImg);
    if (Base64Img['then']) {
      Base64Img['then'](function(base64: string){
        setBase64Img(zip, imgFolder, base64, imgArr, index, downloadName);
        index++;
      },function(err){
        console.log(err);//打印异常信息
      });
    } else {
      setBase64Img(zip, imgFolder, Base64Img, imgArr, index, downloadName);
      index++;
    }
  }
}