base64图片大小计算

字节数转化为kb,MB,GB

  function change(limit) {
    var size = "";
    if (limit < 0.1 * 1024) { //小于0.1KB，则转化成B
      size = limit.toFixed(2) + "B"
    } else if (limit < 0.1 * 1024 * 1024) { //小于0.1MB，则转化成KB
      size = (limit / 1024).toFixed(2) + "KB"
    } else if (limit < 0.1 * 1024 * 1024 * 1024) { //小于0.1GB，则转化成MB
      size = (limit / (1024 * 1024)).toFixed(2) + "MB"
    } else { //其他转化成GB
      size = (limit / (1024 * 1024 * 1024)).toFixed(2) + "GB"
    }

    var sizeStr = size + ""; //转成字符串
    var index = sizeStr.indexOf("."); //获取小数点处的索引
    var dou = sizeStr.substr(index + 1, 2) //获取小数点后两位的值
    if (dou == "00") { //判断后两位是否为00，如果是则删除00                
      return sizeStr.substring(0, index) + sizeStr.substr(index + 3, 2)
    }
    return size;
  }

base64图片大小计算(kb)

  //获取base64图片大小，返回kb数字
  function showSize(base64url) {
    //把头部去掉
    var str = base64url.replace('data:image/png;base64,', '');
    // 找到等号，把等号也去掉
    var equalIndex = str.indexOf('=');
    if(str.indexOf('=')>0) {
        str=str.substring(0, equalIndex);
    }
    // 原来的字符流大小，单位为字节
    var strLength=str.length;
    // 计算后得到的文件流大小，单位为字节
    var fileLength=parseInt(strLength-(strLength/8)*2);
    // 由字节转换为kb
    var size = "";
    size = (fileLength / 1024).toFixed(2);
    var sizeStr = size + ""; //转成字符串
    var index = sizeStr.indexOf("."); //获取小数点处的索引
    var dou = sizeStr.substr(index + 1, 2) //获取小数点后两位的值
    if (dou == "00") { //判断后两位是否为00，如果是则删除00                
      return sizeStr.substring(0, index) + sizeStr.substr(index + 3, 2)
    }
    return size;
  }
  var size = showSize(imagebase64)

 var imagebase64 = 'data:image/png;base64,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'