I'm encountering problems when attempting to display the image/png response from an xmlHTTPRequest. Instead of the correct data, I

Question

I'm encountering problems when attempting to display the image/png response from an xmlHTTPRequest. Instead of the correct data, I

I have implemented the following code to integrate a captcha generating web service. The response data is successfully obtained, but when I attempt to display the result within a div element, the image appears as distorted text.

var xmlHttp = new XMLHttpRequest();
          xmlHttp.onreadystatechange = function() { 
              if (xmlHttp.readyState == 4 && xmlHttp.status == 200)
               { 
              window.alert(xmlHttp.getAllResponseHeaders()); 
                 document.getElementById("captchaDiv2").innerHTML = "<img src=\"data:image/png;base64," + xmlHttp.responseText + "\"/>";
               }
          }
          xmlHttp.open("GET", captchaSrc, true); // true for asynchronous 
          xmlHttp.send(null);

The response header indicates that the type is image/png:

https://i.stack.imgur.com/HG4gK.png However, upon attempting to insert it into the HTML, the output looks like this: https://i.stack.imgur.com/vR8Vp.png

Could you please provide insights on what might be causing this issue? I have already attempted using btoa() with and without encoding, but it did not yield any positive results.

javascript html image css xmlhttprequest

Answer 1

Answer №1

This response references valuable information from a discussion on Stack Overflow (https://stackoverflow.com/a/11562550/266561). In summary, the conversion of XHR strings to base64 encoding can be challenging due to potential corruption when converted to UTF-8, rendering the base64 string invalid. Attempting to use btoa(xmlHttp.responseText) may result in errors in Chrome, particularly with non-ASCII characters present.

However, there is a workaround available. Begin by creating an empty <img id="captchaImg" /> element for easier embedding of the new source. Then,

var xmlHttp = new XMLHttpRequest();
xmlHttp.responseType = "arraybuffer";
xmlHttp.onreadystatechange = function() { 
  if (xmlHttp.readyState == 4 && xmlHttp.status == 200) { 
    document.getElementById("captchaImg").setAttribute('src', 'data:image/png;base64,' + btoa(String.fromCharCode.apply(null, new Uint8Array(xmlHttp.response))));
  }
}
xmlHttp.open("GET", captchaSrc, true); // true for asynchronous
xmlHttp.send(null);

The crucial aspect here is setting

xmlHttp.responseType = "arraybuffer"

to maintain data integrity and prevent corruption. In terms of compatibility, typed arrays are supported from Internet Explorer 10 onwards and even in older versions like Safari 5.1 (the last version for Windows).

Answer 2

This response references valuable information from a discussion on Stack Overflow (https://stackoverflow.com/a/11562550/266561). In summary, the conversion of XHR strings to base64 encoding can be challenging due to potential corruption when converted to UTF-8, rendering the base64 string invalid. Attempting to use btoa(xmlHttp.responseText) may result in errors in Chrome, particularly with non-ASCII characters present.

However, there is a workaround available. Begin by creating an empty <img id="captchaImg" /> element for easier embedding of the new source. Then,

var xmlHttp = new XMLHttpRequest();
xmlHttp.responseType = "arraybuffer";
xmlHttp.onreadystatechange = function() { 
  if (xmlHttp.readyState == 4 && xmlHttp.status == 200) { 
    document.getElementById("captchaImg").setAttribute('src', 'data:image/png;base64,' + btoa(String.fromCharCode.apply(null, new Uint8Array(xmlHttp.response))));
  }
}
xmlHttp.open("GET", captchaSrc, true); // true for asynchronous
xmlHttp.send(null);

The crucial aspect here is setting

xmlHttp.responseType = "arraybuffer"

to maintain data integrity and prevent corruption. In terms of compatibility, typed arrays are supported from Internet Explorer 10 onwards and even in older versions like Safari 5.1 (the last version for Windows).

I'm encountering problems when attempting to display the image/png response from an xmlHTTPRequest. Instead of the correct data, I

Answer №1

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