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HartleySan

Filereader Api'S Readasdataurl Method For External Urls

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I've been playing with the FileReader API recently, and the most interesting method to me is the readAsDataURL method, which allows you to turn a File object into a Base64 string for directly placing image data, etc. into your HTML.

 

This is all well and good for files that I have saved locally, but I'm wondering if there's any way to use this method on external URLs. For example, if I know the URL of an image on the Internet, I'd like to somehow feed that URL to the readAsDataURL method and get back a Base64 string. Is there any way to do this that you all know of?

 

Related to the above, I'm thinking that maybe there's a way to do something similar using PHP, but I don't know off the top of my head. The main thing is that I want to be able to turn images with external URLs into Base64 strings.

 

Thank you.

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Well, after a little more research, I was able to answer my own question.

As it turns out, PHP has all the tools you need to Base64-encode an external image that you have the URL for, and then directly embed that image data into your HTML.

In the event that you want to Base64-encode a local image on your computer though, you're better off using the new HTML5 File and FileReader APIs.

 

Anyway, the following is a sample script I wrote for Base64-encoding any image available via an external URL, and then directly placing that image data in an HTML page:

 

<!DOCTYPE html>

<html lang="en">

 <head>

   <meta charset="UTF-8">

   <title>Directly embedding Base64 images</title>

 </head>

 <body>

   <?php

     $url = 'http://upload.wikimedia.org/wikipedia/en/thumb/8/83/Dark_knight_rises_poster.jpg/220px-Dark_knight_rises_poster.jpg'; // URL to some random Dark Knight Rises movie poster

     $ch = curl_init($url); // I used cURL to get the binary image data. You can also use fopen/fread or file_get_contents, but some sites may block such requests. cURL is better at getting around all this.

     curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

     $img_data = curl_exec($ch); // The binary image data is now in the $img_data variable.

     curl_close($ch);

     $size = getimagesize($url); // In order to display an image using Base64 encoding, you also need the MIME type of the image, which you can get from the getimagesize function.

     echo '<img src="data:' . $size['mime'] . ';base64,' . base64_encode($img_data) . '">'; // This actually displays the image. The 'mime' index contains the MIME type needed. The base64_encode function must be run on the binary image data to make the long Base64 string required to directly embed an image. There is a set format you must use for displaying an image using Base64 encoding. You can get the details on the following page: http://en.wikipedia.org/wiki/Data_URI_scheme

   ?>

 </body>

</html>

 

I hope that helps in the event that anyone else is interested.

Thanks.

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