url 转图片流 / url转base64 / base64 转图片流 / base64转url

1.url 转图片流

// url 转 图片流
const urlToFile = (url, imageName) => {
  return new Promise((resolve, reject) => {
    let blob = null;
    const xhr = new XMLHttpRequest();
    xhr.open("GET", url);
    xhr.setRequestHeader('Accept', 'image/png');
    xhr.responseType = "blob";
    xhr.onload = () => {
      blob = xhr.response;
      let imgFile = new File([blob], imageName, { type: 'image/png' });
      resolve(imgFile);
    };
    xhr.onerror = (e) => {
      reject(e);
    };
    xhr.send();
  });
};
(async () => {
  const baseurl = 'https://img1.baidu.com/it/u=3622442929,3246643478&fm=253&fmt=auto&app=138&f=JPEG?w=889&h=500';
  const file = await urlToFile(baseurl);
  console.log('file', file);
})()

2. url转base64

// url 转 base64
const urlToBase64 =  (url) => {
  return new Promise((resolve, reject) => {
    const image = new Image();  
    image.setAttribute('crossOrigin', 'anonymous');
    image.src = url;  
    image.onload = function(){  
      const canvas = document.createElement("canvas");  
      canvas.width = image.width;  
      canvas.height = image.height;  
      const ctx = canvas.getContext("2d");  
      ctx.drawImage(image, 0, 0, image.width, image.height);  
      const ext = image.src.substring(image.src.lastIndexOf(".")+1).toLowerCase();
      const base64 = canvas.toDataURL("image/"+ext);  
      resolve(base64);
    }
    image.onerror = (e) => {
      reject(e);
    };
  });
}
(async () => {
  const baseurl = 'https://img1.baidu.com/it/u=3622442929,3246643478&fm=253&fmt=auto&app=138&f=JPEG?w=889&h=500';
  const base64 = await urlToBase64(baseurl);
  console.log('base64', base64);
})()

3.base64 转图片流

// base64 转 图片流
const base64ToFile = (base64, filename = 'file') => {
  const arr = base64.split(',');
  const mime = arr[0].match(/:(.*?);/)[1];
  const suffix = mime.split('/')[1];
  const bstr = atob(arr[1]);
  let n = bstr.length;
  const u8arr = new Uint8Array(n);
  while (n--) {
    u8arr[n] = bstr.charCodeAt(n);
  };
  const file = new File([u8arr], `${filename}.${suffix}`, {
    type: mime
  });
  return file;
}

(async () => {
  const baseurl = 'https://img1.baidu.com/it/u=3622442929,3246643478&fm=253&fmt=auto&app=138&f=JPEG?w=889&h=500';
  const base64 = await urlToBase64(baseurl);
  console.log('base64', base64);

  const file = await base64ToFile(base64);
  console.log('file', file);

})()

4.base64转url

// base64 转 图片url
const base64ToUrl = (base64, filename = 'file') => {
  const arr = base64.split(',');
  const mime = arr[0].match(/:(.*?);/)[1];
  const suffix = mime.split('/')[1];
  const bstr = atob(arr[1]);
  let n = bstr.length;
  const u8arr = new Uint8Array(n);
  while (n--) {
    u8arr[n] = bstr.charCodeAt(n);
  };
  const file = new File([u8arr], `${filename}.${suffix}`, {
    type: mime
  });
  return URL.createObjectURL(file);
}

(async () => {
  const baseurl = 'https://img1.baidu.com/it/u=3622442929,3246643478&fm=253&fmt=auto&app=138&f=JPEG?w=889&h=500';
 
  const base64 = await urlToBase64(baseurl);
  console.log('base64', base64);

  const url = await base64ToUrl(base64);
  console.log('url', url);
})()