diff --git a/.gitignore b/.gitignore
index 5e7ab46..8fa8d01 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,4 @@
 node_modules/
+npm-debug.log
 *.actual.css
+*.sublime-*
diff --git a/README.md b/README.md
index e612b87..c08f539 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,29 @@
 PostCSS Assets
 ==============
 
-An asset manager for CSS.
+PostCSS Assets is an asset manager for CSS. It isolates stylesheets from environmental changes, gets image sizes and inlines files.
+
+Table of contents
+-----------------
+
+* [Installation](#installation)
+* [Usage](#usage)
+* [URL resolution](#url-resolution)
+  * [Load paths](#load-paths)
+  * [Base path](#base-path)
+  * [Base URL](#base-url)
+  * [Relative paths](#relative-paths)
+* [Image dimensions](#image-dimensions)
+* [Inlining files](#inlining-files)
+* [Full list of options](#full-list-of-options)
+* [Full list of modifiers](#full-list-of-modifiers)
+
+Installation
+------------
+
+```bash
+npm install postcss-assets --save-dev
+```
 
 Usage
 -----
@@ -14,7 +36,9 @@ gulp.task('assets', function () {
   var assets  = require('postcss-assets');
 
   return gulp.src('source/*.css')
-    .pipe(postcss([ assets() ]))
+    .pipe(postcss([assets({
+      loadPaths: ['images/']
+    })]))
     .pipe(gulp.dest('build/'));
 });
 ```
@@ -28,10 +52,123 @@ grunt.initConfig({
   postcss: {
     options: {
       processors: [
-        assets().postcss
+        assets({
+          loadPaths: ['images/']
+        })
       ]
     },
     dist: { src: 'build/*.css' }
   },
 });
 ```
+
+URL resolution
+--------------
+
+These options isolate stylesheets from environmental changes.
+
+### Load paths
+
+To make PostCSS Assets search for files in specific directories, define load paths:
+
+```js
+var options = {
+  loadPaths: ['fonts/', 'media/patterns/', 'images/']
+};
+```
+
+Example:
+
+```css
+body {
+  background: url('foobar.jpg');
+  background: url('icons/baz.png');
+}
+```
+
+PostCSS Assets would look for the files in load paths, then in the base path. If it succeed, it would resolve a true URL:
+
+```css
+body {
+  background: url('/media/patterns/foobar.jpg');
+  background: url('/images/icons/baz.png');
+}
+```
+
+### Base path
+
+If the root directory of your site is not where you execute PostCSS Assets, correct it:
+
+```js
+var options = {
+  basePath: 'source/'
+};
+```
+
+PostCSS Assets would treat `source` directory as `/` for all URLs and load paths would be relative to it.
+
+### Base URL
+
+If the URL of your base path is not `/`, correct it:
+
+```js
+var options = {
+  baseUrl: 'http://example.com/wp-content/themes/'
+};
+```
+
+### Relative paths
+
+To make resolved paths relative, define a directory to relate to:
+
+```js
+var options = {
+  relativeTo: 'assets/css'
+};
+```
+
+Image dimensions
+----------------
+
+PostCSS Assets calculates dimensions of PNG, JPEG, GIF, SVG and WebP images:
+
+```css
+body {
+  width: width('images/foobar.png'); /* 320px */
+  height: height('images/foobar.png'); /* 240px */
+  background-size: size('images/foobar.png'); /* 320px 240px */
+}
+```
+
+To correct the dimensions for images with a high density, pass it as a second parameter:
+
+```css
+body {
+  width: width('images/foobar.png', 2); /* 160px */
+  height: height('images/foobar.png', 2); /* 120px */
+  background-size: size('images/foobar.png', 2); /* 160px 120px */
+}
+```
+
+Inlining files
+--------------
+
+PostCSS inlines files to a stylesheet in Base64 encoding:
+
+```css
+body {
+  background: inline('images/foobar.png');
+}
+```
+
+SVG files would be inlined unencoded, because [then they benefit in size](http://css-tricks.com/probably-dont-base64-svg/).
+
+Full list of options
+--------------------
+
+| Option           | Description                                                                     | Default |
+|:-----------------|:--------------------------------------------------------------------------------|:--------|
+| `basePath`       | Root directory of the project.                                                  | `.`     |
+| `baseUrl`        | URL of the project when running the web server.                                 | `/`     |
+| `loadPaths`      | Specific directories to look for the files.                                     | `[]`    |
+| `relativeTo`     | Directory to relate to when resolving URLs. If `false`, disables relative URLs. | `false` |
diff --git a/index.js b/index.js
index 0630e2b..9871c3d 100644
--- a/index.js
+++ b/index.js
@@ -13,17 +13,6 @@ var cssesc = require('cssesc');
 var mime = require('mime');
 var sizeOf = require('image-size');
 
-const AUTO_SIZE   = ['background-size', 'border-image-width', 'border-width',
-                     'margin', 'padding'];
-const AUTO_WIDTH  = ['border-left', 'border-left-width', 'border-right',
-                     'border-right-width', 'left', 'margin-left',
-                     'margin-right', 'max-width', 'min-width', 'padding-left',
-                     'padding-right', 'width'];
-const AUTO_HEIGHT = ['border-bottom', 'border-bottom-width', 'border-top',
-                     'border-top-width', 'bottom', 'height', 'margin-bottom',
-                     'margin-top', 'max-height', 'min-height',
-                     'padding-bottom', 'padding-top'];
-
 module.exports = function (options) {
 
   options = options || {};
@@ -50,6 +39,25 @@ module.exports = function (options) {
     options.relativeTo = false;
   }
 
+  function getImageSize(assetStr, density) {
+    var assetPath = resolvePath(assetStr.value);
+    var size;
+    try {
+      size = sizeOf(assetPath);
+      if (typeof density !== 'undefined') {
+        density = parseFloat(density.value, 10);
+        console.log(density);
+        size.width  = +(size.width  / density).toFixed(4);
+        size.height = +(size.height / density).toFixed(4);
+      }
+      return size;
+    } catch (exception) {
+      var err = new Error("Image corrupted: " + assetPath);
+      err.name = 'ECORRUPT';
+      throw err;
+    }
+  }
+
   function matchPath(assetPath) {
     var exception, matchingPath;
     var isFound = options.loadPaths.some(function (loadPath) {
@@ -95,50 +103,45 @@ module.exports = function (options) {
     return cssesc(url.format(assetUrl));
   }
 
-  function shouldBeInline(assetPath) {
-    if (options.inline && options.inline.maxSize) {
-      var size = fs.statSync(assetPath).size;
-      return (size <= parseBytes(options.inline.maxSize));
-    }
-    return false;
-  }
-
   return function (cssTree) {
     cssTree.eachDecl(function (decl) {
-
-      decl.value = mapFunctions(decl.value, function (before, quote, assetStr, modifier, after) {
-
-        try {
-
-          var assetPath = resolvePath(assetStr);
-          var prop = vendor.unprefixed(decl.prop);
-
-          if (modifier === 'width' || AUTO_WIDTH.indexOf(prop) !== -1) {
-            return sizeOf(assetPath).width + 'px';
-          }
-
-          if (modifier === 'height' || AUTO_HEIGHT.indexOf(prop) !== -1) {
-            return sizeOf(assetPath).height + 'px';
-          }
-
-          if (modifier === 'size' || AUTO_SIZE.indexOf(prop) !== -1) {
-            var size = sizeOf(assetPath);
+      try {
+        decl.value = mapFunctions(decl.value, {
+          'url': function (assetStr) {
+            assetStr.value = resolveUrl(assetStr.value);
+            return 'url(' + assetStr + ')';
+          },
+
+          'inline': function (assetStr) {
+            assetStr.value = resolveDataUrl(assetStr.value);
+            return 'url(' + assetStr + ')';
+          },
+
+          'width': function (assetStr, density) {
+            return getImageSize(assetStr, density).width  + 'px';
+          },
+
+          'height': function (assetStr, density) {
+            return getImageSize(assetStr, density).height + 'px';
+          },
+
+          'size': function (assetStr, density) {
+            var size = getImageSize(assetStr, density);
             return size.width + 'px ' + size.height + 'px';
           }
-
-          if (shouldBeInline(assetPath)) {
-            return 'url(' + before + quote + resolveDataUrl(assetStr) + quote + after + ')';
-          }
-
-          return 'url(' + before + quote + resolveUrl(assetStr) + quote + after + ')';
-
-        } catch (exception) {
-          if (exception.name !== 'ENOENT') {
-            throw exception;
-          }
+        });
+      } catch (exception) {
+        switch (exception.name) {
+        case 'ECORRUPT':
+          console.warn(exception.message);
+          break;
+        case 'ENOENT':
           console.warn('%s\nLoad paths:\n  %s', exception.message, options.loadPaths.join('\n  '));
+          break;
+        default:
+          throw exception;
         }
-      });
+      }
     });
   };
 };
diff --git a/lib/mapFunctions.js b/lib/mapFunctions.js
index 6450912..e87f07e 100644
--- a/lib/mapFunctions.js
+++ b/lib/mapFunctions.js
@@ -1,12 +1,56 @@
-const R_FUNC = /url\((\s*)((['"]?).*?\3.*?)(\s*)\)/gi;
-const R_PARAMS = /^(['"]?)(.+?)\1(?:\s+(.+))?$/;
-
-module.exports = function mapFunctions(cssValue, callback) {
-  return cssValue.replace(R_FUNC, function (matches, before, params, quote, after) {
-    params = params.match(R_PARAMS);
-    var assetStr = params[2];
-    var modifier = params[3];
-    var result = callback(before, quote, assetStr, modifier, after);
-    return result || matches;
-  });
+var gonzales = require('gonzales');
+var list = require('postcss/lib/list');
+
+function CSSString (str) {
+  this.quotes = str[0];
+
+  if (this.quotes === "'" || this.quotes === '"') {
+    this.value = str.slice(1, -1);
+  } else {
+    this.value = str;
+    this.quotes = '';
+  }
+}
+
+CSSString.prototype.toString = function () {
+  return this.quotes + this.value + this.quotes;
+};
+
+module.exports = function mapFunctions(cssValue, map) {
+  var ast = gonzales.srcToCSSP(cssValue, 'value');
+
+  var traverse = function (node) {
+    var type = node[0];
+    var children = node.slice(1);
+
+    if (type === 'uri') {
+      node = gonzales.srcToCSSP(gonzales.csspToSrc(node), 'funktion');
+      return traverse(node);
+    }
+
+    if (type === 'funktion') {
+      var name = children[0][1];
+      var body = children[1].slice(1).map(function (x) {
+        return gonzales.csspToSrc(traverse(x));;
+      }).join('');
+
+      var process = map[name];
+
+      if (typeof process === 'function') {
+        return ['raw', process.apply(this, list.comma(body).map(function (param) {
+          return new CSSString(param);
+        }))];
+      }
+    }
+
+    return [type].concat(children.map(function (child) {
+      if (Array.isArray(child)) {
+        return traverse(child);
+      }
+
+      return child;
+    }));
+  };
+
+  return gonzales.csspToSrc(traverse(ast));
 };
diff --git a/package.json b/package.json
index 0bc6c07..d0d5297 100644
--- a/package.json
+++ b/package.json
@@ -1,22 +1,23 @@
 {
   "name": "postcss-assets",
-  "version": "0.9.1",
+  "version": "1.0.0",
   "description": "PostCSS plugin to manage assets",
   "author": "Vadim Borodean <borodean@gmail.com>",
   "license": "MIT",
   "repository": {
     "type": "git",
-    "url":  "https://github.com/borodean/postcss-assets"
+    "url": "https://github.com/borodean/postcss-assets"
   },
   "dependencies": {
     "cssesc": "^0.1.0",
-    "image-size": "^0.3.3",
+    "gonzales": "^1.0.7",
+    "image-size": "^0.3.5",
     "js-base64": "^2.1.5",
     "mime": "^1.2.11",
-    "postcss": "^2.2.5"
+    "postcss": "^3.0.7"
   },
   "devDependencies": {
-    "tape": "^3.0.0"
+    "tape": "^3.0.3"
   },
   "scripts": {
     "test": "tape test"
diff --git a/test/fixtures/alpha/invalid.jpg b/test/fixtures/alpha/invalid.jpg
new file mode 100644
index 0000000..e40413f
--- /dev/null
+++ b/test/fixtures/alpha/invalid.jpg
@@ -0,0 +1 @@
+Wishmaster
diff --git a/test/fixtures/dimensions.css b/test/fixtures/dimensions.css
index 947bf6a..09c7aab 100644
--- a/test/fixtures/dimensions.css
+++ b/test/fixtures/dimensions.css
@@ -1,43 +1,12 @@
 body {
-  width: url('beta/maria.jpg' width);
-  height: url('beta/maria.jpg' height);
-  height: url('beta/maria.jpg?foo=bar#baz' height);
-  width: url('beta/maria.jpg');
-  height: url('beta/maria.jpg');
-  background-size: url('beta/maria.jpg' size);
-  -webkit-background-size: url('beta/maria.jpg');
-     -moz-background-size: url('beta/maria.jpg');
-          background-size: url('beta/maria.jpg');
+  background-size: size('beta/maria.jpg');
+  width: width('beta/maria.jpg');
+  height: height('beta/maria.jpg');
 
-  background-size: url('beta/maria.jpg');
-  border-image-width: url('beta/maria.jpg');
-  border-width: url('beta/maria.jpg');
-  margin: url('beta/maria.jpg');
-  padding: url('beta/maria.jpg');
+  width: width('beta/maria.jpg', 2);
+  height: height('beta/maria.jpg', 2);
 
-  border-left: url('beta/maria.jpg') solid red;
-  border-left-width: url('beta/maria.jpg');
-  border-right: dashed url('beta/maria.jpg') blue;
-  border-right-width: url('beta/maria.jpg');
-  left: url('beta/maria.jpg');
-  margin-left: url('beta/maria.jpg');
-  margin-right: url('beta/maria.jpg');
-  max-width: url('beta/maria.jpg');
-  min-width: url('beta/maria.jpg');
-  padding-left: url('beta/maria.jpg');
-  padding-right: url('beta/maria.jpg');
-  width: url('beta/maria.jpg');
+  width: width('beta/maria.jpg', 1.3);
 
-  border-bottom: double green url('beta/maria.jpg');
-  border-bottom-width: url('beta/maria.jpg');
-  border-top: black url('beta/maria.jpg') solid;
-  border-top-width: url('beta/maria.jpg');
-  bottom: url('beta/maria.jpg');
-  height: url('beta/maria.jpg');
-  margin-bottom: url('beta/maria.jpg');
-  margin-top: url('beta/maria.jpg');
-  max-height: url('beta/maria.jpg');
-  min-height: url('beta/maria.jpg');
-  padding-bottom: url('beta/maria.jpg');
-  padding-top: url('beta/maria.jpg');
+  width: width('alpha/invalid.jpg');
 }
diff --git a/test/fixtures/dimensions.expected.css b/test/fixtures/dimensions.expected.css
index 85cab24..7622a19 100644
--- a/test/fixtures/dimensions.expected.css
+++ b/test/fixtures/dimensions.expected.css
@@ -1,43 +1,12 @@
 body {
+  background-size: 45px 60px;
   width: 45px;
   height: 60px;
-  height: 60px;
-  width: 45px;
-  height: 60px;
-  background-size: 45px 60px;
-  -webkit-background-size: 45px 60px;
-     -moz-background-size: 45px 60px;
-          background-size: 45px 60px;
 
-  background-size: 45px 60px;
-  border-image-width: 45px 60px;
-  border-width: 45px 60px;
-  margin: 45px 60px;
-  padding: 45px 60px;
+  width: 22.5px;
+  height: 30px;
 
-  border-left: 45px solid red;
-  border-left-width: 45px;
-  border-right: dashed 45px blue;
-  border-right-width: 45px;
-  left: 45px;
-  margin-left: 45px;
-  margin-right: 45px;
-  max-width: 45px;
-  min-width: 45px;
-  padding-left: 45px;
-  padding-right: 45px;
-  width: 45px;
+  width: 34.6154px;
 
-  border-bottom: double green 60px;
-  border-bottom-width: 60px;
-  border-top: black 60px solid;
-  border-top-width: 60px;
-  bottom: 60px;
-  height: 60px;
-  margin-bottom: 60px;
-  margin-top: 60px;
-  max-height: 60px;
-  min-height: 60px;
-  padding-bottom: 60px;
-  padding-top: 60px;
+  width: width('alpha/invalid.jpg');
 }
diff --git a/test/fixtures/inline.css b/test/fixtures/inline.css
index f188033..f80d95f 100644
--- a/test/fixtures/inline.css
+++ b/test/fixtures/inline.css
@@ -1,7 +1,6 @@
 body {
-  background: url('alpha/blank.gif');
-  background: url(  'alpha/blank.gif' );
-  background: url('alpha/kateryna.jpg');
-  background: url('alpha/trapezium.svg');
-  background: url('alpha/trapezium-single-quotes.svg');
+  background: inline('alpha/blank.gif');
+  background: inline(  'alpha/blank.gif' );
+  background: inline('alpha/trapezium.svg');
+  background: inline('alpha/trapezium-single-quotes.svg');
 }
diff --git a/test/fixtures/inline.expected.css b/test/fixtures/inline.expected.css
index 0bdff64..a3e32aa 100644
--- a/test/fixtures/inline.expected.css
+++ b/test/fixtures/inline.expected.css
@@ -1,7 +1,6 @@
 body {
   background: url('data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACH5BAAAAAAALAAAAAABAAEAAAICRAEAOw==');
-  background: url(  'data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACH5BAAAAAAALAAAAAABAAEAAAICRAEAOw==' );
-  background: url('/alpha/kateryna.jpg');
+  background: url('data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACH5BAAAAAAALAAAAAABAAEAAAICRAEAOw==');
   background: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" width="160" height="120">\D\A   <path fill="#4D4D4D" d="M160 120h-160l40-120h80z"/>\D\A</svg>\D\A');
   background: url('data:image/svg+xml;utf8,<svg xmlns=\'http://www.w3.org/2000/svg\' width=\'160\' height=\'120\'>\D\A   <path fill=\'#4D4D4D\' d=\'M160 120h-160l40-120h80z\'/>\D\A</svg>\D\A');
 }
diff --git a/test/fixtures/resolve-spelling.expected.css b/test/fixtures/resolve-spelling.expected.css
index 3214a4e..3c5ee51 100644
--- a/test/fixtures/resolve-spelling.expected.css
+++ b/test/fixtures/resolve-spelling.expected.css
@@ -1,7 +1,7 @@
 body {
   color: red;
   background: url(/alpha/kateryna.jpg);
-  background: url(  /alpha/kateryna.jpg );
+  background: url(/alpha/kateryna.jpg);
   background: no-repeat url(/alpha/kateryna.jpg) #000;
   background:
     url('/alpha/kateryna.jpg'),
diff --git a/test/index.js b/test/index.js
index 49d52a7..40311dd 100644
--- a/test/index.js
+++ b/test/index.js
@@ -72,14 +72,7 @@ test('path resolving', function (t) {
 });
 
 test('path inlining', function (t) {
-
-  compareFixtures(t, 'inline', 'base64-encodes matching assets', {
-    basePath: 'test/fixtures/',
-    inline: {
-      maxSize: '2K'
-    }
-  });
-
+  compareFixtures(t, 'inline', 'base64-encodes assets', { basePath: 'test/fixtures/' });
   t.end();
 });
 
diff --git a/test/lib/mapFunctions.js b/test/lib/mapFunctions.js
index 2735bc1..003b183 100644
--- a/test/lib/mapFunctions.js
+++ b/test/lib/mapFunctions.js
@@ -2,36 +2,70 @@ var test = require('tape');
 
 var mapFunctions = require('../../lib/mapFunctions');
 
-function compact(arr) {
-  return Array.prototype.filter.call(arr, function (i) { return i; });
-}
+const MAP = {
+  'decrease': function (params) {
+    return parseFloat(params, 10) - 1 + 'px';
+  },
+  'increase': function (params) {
+    return parseFloat(params, 10) + 1 + 'px';
+  },
+  'double': function (params) {
+    return parseFloat(params, 10) * 2 + 'px';
+  },
+  'url': function (params) {
+    return 'url(https://github.com/' + params + ')';
+  },
+  'combine': function (a, b) {
+    return parseFloat(a, 10) + parseFloat(b, 10) + 'px';
+  }
+};
 
-function checkArgs(t, input, expected, msg) {
-  var actual = [];
-  mapFunctions(input, function () {
-    actual = actual.concat(compact(arguments));
-  });
-  t.deepEqual(actual, expected, msg);
+function checkMapping (t, source, expectedResult, msg) {
+  t.equal(mapFunctions(source, MAP), expectedResult, msg);
 }
 
 test('mapFunctions', function (t) {
+  checkMapping(t,
+    'increase(100px)',
+    '101px',
+    'maps functions'
+  );
+
+  checkMapping(t,
+    'increase(100px), decrease(100px)',
+    '101px, 99px',
+    'maps sibling functions'
+  );
 
-  checkArgs(t, 'url(kateryna.jpg)', ['kateryna.jpg'], 'parses unquoted param');
-  checkArgs(t, 'url(\'kateryna.jpg\')', ['\'', 'kateryna.jpg'], 'parses single-quoted param');
-  checkArgs(t, 'url("kateryna.jpg")', ['"', 'kateryna.jpg'], 'parses double-quoted param');
-  checkArgs(t, 'url("kateryna_(shevchenko).jpg")', ['"', 'kateryna_(shevchenko).jpg'], 'parses param with parentheses');
+  checkMapping(t,
+    'double(increase(100px))',
+    '202px',
+    'maps nested functions'
+  );
 
-  checkArgs(t, 'url("Gupsy Fortuneteller.jpg")', ['"', 'Gupsy Fortuneteller.jpg'], 'parses param with spaces');
-  checkArgs(t, 'url(\'Baba O\\\'Riley.jpg\')', ['\'', 'Baba O\\\'Riley.jpg'], 'parses param escaped quotes');
+  checkMapping(t,
+    'unknown(100px)',
+    'unknown(100px)',
+    'skips unknown functions'
+  );
 
-  checkArgs(t, 'url(kateryna.jpg width)', ['kateryna.jpg', 'width'], 'parses unquoted param with modifier');
-  checkArgs(t, 'url(kateryna.jpg  width)', ['kateryna.jpg', 'width'], 'parses unquoted param with modifier with extra space');
-  checkArgs(t, 'url("kateryna.jpg" width)', ['"', 'kateryna.jpg', 'width'], 'parses quoted param with modifier');
+  checkMapping(t,
+    'unknown(increase(100px))',
+    'unknown(101px)',
+    'maps inside unknown functions'
+  );
 
-  checkArgs(t, 'url(  kateryna.jpg )', ['  ', 'kateryna.jpg', ' '], 'parses extra space');
+  checkMapping(t,
+    'url(borodean)',
+    'url(https://github.com/borodean)',
+    'maps urls as functions'
+  );
 
-  checkArgs(t, '#000 url(kateryna.jpg) no-repeat', ['kateryna.jpg'], 'parses complex values');
-  checkArgs(t, 'url(kateryna.jpg), url(odalisque.jpg)', ['kateryna.jpg', 'odalisque.jpg'], 'parses multiple values');
+  checkMapping(t,
+    'combine(20px, 15px)',
+    '35px',
+    'accepts multiple parameters'
+  );
 
   t.end();
 });