title: JavaScript BLOB coming out much larger than the input
body: <p>We receive a local file (typically a PDF, PNG or JPG) by drag and drop in a variable (using dropzone.js - at this stage it's base64 plus the characters to specify the file type).  We encrypt it (now it's binary) into a javascript variable.  We then create a Blob using that variable and upload it to a server running PHP.  (See <a href="https://stackoverflow.com/questions/29791961/how-to-send-javascript-variable-to-php-server-as-file">our finding out how to send a js variable to PHP $_FILE</a>.) </p>
  
  <p>We are finding that the .size of the blob is about 50% larger than the .length of the file we are uploading.  (We had been uploading by converting to base64 then uploading with JSON, but one reason we are looking to change is to hopefully avoid the 33% bump in size from using base64.)</p>
  
  <p>The blob is consistently about 50% larger from moderate sizes up to larger sizes.  As a small test, we created a Blob using 120 chars as input and found the Blob.size to be 210.  (We normally use the correct file.type; image/png was just to have it be interpreted as binary data that didn't need encoding.)  From actual use in our code:  we uploaded a 900K PDF file. Type was something like 'application/pdf'. The resultant blob was like 1,400K. Also tried with PNG. </p>
  
  <p>I would think that the Blob should be about the same size as the input,no? What might we be doing wrong?</p>
  
  <pre><code>new Blob(["123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890"], {type:"image/png"});
  </code></pre>