使用 JavaScript 显示一个 Blob

Question

I am retrieving a Blob image from a database, and I'd like to be able to view that image using JavaScript. The following code produces a broken image icon on the page:

var image = document.createElement('image');
    image.src = 'data:image/bmp;base64,'+Base64.encode(blob);
    document.body.appendChild(image);

Here is a jsFiddle containing all the code required, including the blob. The completed code should properly display an image.

Answer 1

You can also get BLOB object directly from XMLHttpRequest. Setting responseType to blob makes the trick. Here is my code:

var xhr = new XMLHttpRequest();
xhr.open("GET", "http://localhost/image.jpg");
xhr.responseType = "blob";
xhr.onload = response;
xhr.send();

And the response function looks like this:

function response(e) {
   var urlCreator = window.URL || window.webkitURL;
   var imageUrl = urlCreator.createObjectURL(this.response);
   document.querySelector("#image").src = imageUrl;
}

We just have to make an empty image element in HTML:

<img id="image"/>

Answer 2

If you want to use fetch instead:

var myImage = document.querySelector('img');

fetch('flowers.jpg').then(function(response) {
  return response.blob();
}).then(function(myBlob) {
  var objectURL = URL.createObjectURL(myBlob);
  myImage.src = objectURL;
});

Source:

https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch

Answer 3

You can convert your string into a Uint8Array to get the raw data. Then create a Blob for that data and pass to URL.createObjectURL(blob) to convert the Blob into a URL that you pass to img.src .

var data = '424D5E070000000000003E00000028000000EF...';

// Convert the string to bytes
var bytes = new Uint8Array(data.length / 2);

for (var i = 0; i < data.length; i += 2) {
    bytes[i / 2] = parseInt(data.substring(i, i + 2), /* base = */ 16);
}

// Make a Blob from the bytes
var blob = new Blob([bytes], {type: 'image/bmp'});

// Use createObjectURL to make a URL for the blob
var image = new Image();
image.src = URL.createObjectURL(blob);
document.body.appendChild(image);

You can try the complete example at: http://jsfiddle.net/nj82y73d/

Answer 4

In your example, you should createElement('img') .

In your link, base64blob != Base64.encode(blob) .

This works, as long as your data is valid http://jsfiddle.net/SXFwP/ (I didn't have any BMP images so I had to use PNG).

Answer 5

I guess you had an error in the inline code of your image. Try this :

 var image = document.createElement('img'); image.src="data:image/gif;base64,R0lGODlhDwAPAKECAAAAzMzM/////wAAACwAAAAADwAPAAACIISPeQHsrZ5ModrLlN48CXF8m2iQ3YmmKqVlRtW4MLwWACH+H09wdGltaXplZCBieSBVbGVhZCBTbWFydFNhdmVyIQAAOw=="; image.width=100; image.height=100; image.alt="here should be some image"; document.body.appendChild(image);

Helpful link : http://dean.edwards.name/my/base64-ie.html

Answer 6

The problem was that I had hexadecimal data that needed to be converted to binary before being base64encoded.

in PHP:

base64_encode(pack("H*", $subvalue))

Answer 7

In the fiddle your blob isn't a blob, it's a string representation of hexadecimal data. Try this on a blob and your done

var image = document.createElement('img');
let reader=new FileReader()
reader.addEventListener('loadend',()=>{
  let contents=reader.result
  image.src = contents
  document.body.appendChild(image);
})
if(blob instanceof Blob) reader.readAsDataURL(blob)

readAsDataURL give you a base64 encoded image ready for you image element () source (src)

Answer 8

我也尝试在我的网站上给出答案： http : //bharatbaba.com/how-to-display-blob-image-in-html-using-javascript-and-php.htm