Working entirely on the client side, I intend to use an HTTP service that responds to a POST request by sending a BMP file with the response type set to image/bmp.

How can I draw this image to an HTML canvas object using JavaScirpt?

Here's a piece of code that results in a gibberish image (due to an incorrect processing of raw binary data?):

 function refresh() {
     var request = new XMLHttpRequest();
     request.open('POST', 'imgview');
     request.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
     request.setRequestHeader('Response-Type', 'image/bmp');
     request.onload = function(event) {
         if (request.status >= 200 && request.status < 300) {
             var blob = new Blob([request.response], {type: 'image/bmp'});
             var imageURL = window.URL.createObjectURL(blob); 
             var image = new Image;
             image.crossOrigin = "Anonymous";
             image.onload = function() {
                 console.log(image.width)
                 document.body.appendChild(image);
                 var canvas = document.getElementById("canvas");
                 var context = canvas.getContext('2d');
                 context.drawImage(image, 0, 0);
             }
             image.src = imageURL;
         } else {
             // [...]
         }
     };

// [...]
request.send(requestText);