modernizr/feature-detects/url/data-uri.js

Modernizr is a JavaScript library that detects HTML5 and CSS3 features in the user’s browser.

/*!
{
  "name": "Data URI",
  "property": "datauri",
  "caniuse": "datauri",
  "tags": ["url"],
  "builderAliases": ["url_data_uri"],
  "async": true,
  "notes": [{
    "name": "Wikipedia article",
    "href": "https://en.wikipedia.org/wiki/Data_URI_scheme"
  }],
  "warnings": ["Support in Internet Explorer 8 is limited to images and linked resources like CSS files, not HTML files"]
}
!*/
/* DOC
Detects support for data URIs. Provides a subproperty to report support for data URIs over 32kb in size:

```javascript
Modernizr.datauri           // true
Modernizr.datauri.over32kb  // false in IE8
```
*/
define(['Modernizr', 'addTest'], function(Modernizr, addTest) {
  // https://github.com/Modernizr/Modernizr/issues/14
  Modernizr.addAsyncTest(function() {

    // IE7 throw a mixed content warning on HTTPS for this test, so we'll
    // just blacklist it (we know it doesn't support data URIs anyway)
    // https://github.com/Modernizr/Modernizr/issues/362
    if (navigator.userAgent.indexOf('MSIE 7.') !== -1) {
      // Keep the test async
      setTimeout(function() {
        addTest('datauri', false);
      }, 10);
    }

    var datauri = new Image();

    datauri.onerror = function() {
      addTest('datauri', false);
    };
    datauri.onload = function() {
      if (datauri.width == 1 && datauri.height == 1) {
        testOver32kb();
      }
      else {
        addTest('datauri', false);
      }
    };

    datauri.src = 'data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///ywAAAAAAQABAAACAUwAOw==';

    // Once we have datauri, let's check to see if we can use data URIs over
    // 32kb (IE8 can't). https://github.com/Modernizr/Modernizr/issues/321
    function testOver32kb() {

      var datauriBig = new Image();

      datauriBig.onerror = function() {
        addTest('datauri', true);
        Modernizr.datauri = new Boolean(true);
        Modernizr.datauri.over32kb = false;
      };
      datauriBig.onload = function() {
        addTest('datauri', true);
        Modernizr.datauri = new Boolean(true);
        Modernizr.datauri.over32kb = (datauriBig.width == 1 && datauriBig.height == 1);
      };

      var base64str = 'R0lGODlhAQABAIAAAAAAAP///ywAAAAAAQABAAACAUwAOw==';
      while (base64str.length < 33000) {
        base64str = '\r\n' + base64str;
      }
      datauriBig.src = 'data:image/gif;base64,' + base64str;
    }

  });
});