guess the mimetype, and properly encode non-base64 uris

lib/less/functions.js

@@ -351,18 +351,34 @@ tree.functions = {
             throw new Error('data-uri() is not supported in the browser.');
         }
 
-        var fs = require('fs');
-
-        var data = fs.readFileSync(path.value);
         mimetype = mimetype.value;
+        path = (path && path.value);
 
-        if (/;base64$/.test(mimetype)) {
-          data = (new Buffer(data)).toString('base64');
+        var fs = require('fs');
+        var useBase64 = false;
+
+        // detect the mimetype if not given
+        if (arguments.length < 2) {
+            var mime = require('mime');
+            path = mimetype;
+            mimetype = mime.lookup(path);
+
+            // use base 64 unless it's an ASCII or UTF-8 format
+            var charset = mime.charsets.lookup(mimetype);
+            useBase64 = ['US-ASCII', 'UTF-8'].indexOf(charset) < 0;
+            if (useBase64) mimetype += ';base64';
+        }
+        else {
+            useBase64 = /;base64$/.test(mimetype)
         }
 
-        var contents = new(tree.Anonymous)('data:'+mimetype+','+data);
+        var buf = fs.readFileSync(path);
 
-        return new(tree.URL)(contents);
+        buf = useBase64 ? buf.toString('base64')
+                        : encodeURIComponent(buf);
+
+        var uri = "'data:"+mimetype+','+buf+"'";
+        return new(tree.URL)(new(tree.Anonymous)(uri));
     }
 };
 

package.json

@@ -10,7 +10,7 @@
   "main"          : "./lib/less/index",
   "directories"   : { "test": "./test" },
   "engines"       : { "node": ">=0.4.2" },
-  "optionalDependencies" : { "ycssmin": ">=1.0.1" },
+  "optionalDependencies" : { "ycssmin": ">=1.0.1", "mime": "1.2.x" },
   "devDependencies" : { "diff": "~1.0" },
   "scripts": {
    "test": "make test"

test/css/functions.css

@@ -100,5 +100,12 @@
   negation: #d73131;
 }
 #data-uri {
-  background-image: url(data:image/jpeg;base64,bm90IGFjdHVhbGx5IGEganBlZyBmaWxlCg==);
+  uri: url('data:image/jpeg;base64,bm90IGFjdHVhbGx5IGEganBlZyBmaWxlCg==');
+}
+#data-uri-guess {
+  uri: url('data:image/jpeg;base64,bm90IGFjdHVhbGx5IGEganBlZyBmaWxlCg==');
+}
+#data-uri-ascii {
+  uri-1: url('data:text/html,%3Ch1%3EThis%20page%20is%20100%25%20Awesome.%3C%2Fh1%3E%0A');
+  uri-2: url('data:text/html,%3Ch1%3EThis%20page%20is%20100%25%20Awesome.%3C%2Fh1%3E%0A');
 }

test/data/page.html

@@ -0,0 +1 @@
+<h1>This page is 100% Awesome.</h1>

test/less/functions.less

@@ -112,5 +112,14 @@
 }
 
 #data-uri {
-  background-image: data-uri('image/jpeg;base64', 'test/data/image.jpg');
+  uri: data-uri('image/jpeg;base64', 'test/data/image.jpg');
+}
+
+#data-uri-guess {
+  uri: data-uri('test/data/image.jpg');
+}
+
+#data-uri-ascii {
+  uri-1: data-uri('text/html', 'test/data/page.html');
+  uri-2: data-uri('test/data/page.html');
 }