js 图片转换base64 base64转换为file对象 base64转图片

将图片转换为Base64

function getImgToBase64(url,callback){
  var canvas = document.createElement('canvas'),
    ctx = canvas.getContext('2d'),
    img = new Image;
  img.crossOrigin = 'Anonymous';
  img.onload = function(){
    canvas.height = img.height;
    canvas.width = img.width;
    ctx.drawImage(img,0,0);
    var dataURL = canvas.toDataURL('image/png');
    callback(dataURL);
    canvas = null;
  };
  img.src = url;
}

将base64转换为file类型

 function dataURLtoFile(dataurl, filename) {
     var arr = dataurl.split(','), mime = arr[0].match(/:(.*?);/)[1],
     bstr = atob(arr[1]), n = bstr.length, u8arr = new Uint8Array(n);
     while(n--){
       u8arr[n] = bstr.charCodeAt(n);
    }
    return new File([u8arr], filename, {type:mime});
 }

可以将图片转换为base64

getImgToBase64('img/test.png',function(data){
　　var myFile = dataURLtoFile(data,'testimgtestimgtestimg');
　　console.log(myFile);
});

Base64 转化成图片格式

      function dataURLtoFile(dataurl, filename = 'file') {
          let arr = dataurl.split(',')
          let mime = arr[0].match(/:(.*?);/)[1]
          let suffix = mime.split('/')[1]
          let bstr = atob(arr[1])
          let n = bstr.length
          let u8arr = new Uint8Array(n)
          while (n--) {
              u8arr[n] = bstr.charCodeAt(n)
          }
          return new File([u8arr], `${filename}.${suffix}`, {
              type: mime
          })
      }
      var base64Img = imgDataUrl // base64编码的图片
      var imgFile = dataURLtoFile(base64Img)
      console.log('imgFile====>', imgFile)