diff --git a/docs/index.rst b/docs/index.rst
index 08abd78..75585ad 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -11,4 +11,5 @@ Documentation
    configuration
    album_information
    themes
+   plugins
    changelog
diff --git a/docs/plugins.rst b/docs/plugins.rst
new file mode 100644
index 0000000..95b7c12
--- /dev/null
+++ b/docs/plugins.rst
@@ -0,0 +1,86 @@
+=========
+ Plugins
+=========
+
+How to use plugins
+------------------
+
+Plugins must be specified with the ``plugins`` setting:
+
+.. code-block:: python
+
+   from sigal.plugins import copyright
+   plugins = ['sigal.plugins.adjust', copyright]
+
+You can either specify the name of the module which contains the plugin, or
+import the plugin before adding it to the list. The ``plugin_paths`` setting
+can be used to specify paths to search for plugins (if they are not in the
+python path).
+
+Write a new plugin
+------------------
+
+Plugins are based on signals with the blinker_ library. A plugin must
+subscribe to a signal (the list is given below). New signals can be added if
+need. See an example with the copyright plugin:
+
+.. _blinker: http://pythonhosted.org/blinker/
+
+.. literalinclude:: ../sigal/plugins/copyright.py
+   :language: python
+
+Signals
+-------
+
+.. function:: sigal.signals.album_initialized(album)
+   :noindex:
+
+   Called after the :class:`~sigal.gallery.Album` is initialized.
+
+   :param album: the :class:`~sigal.gallery.Album` object.
+
+.. data:: sigal.signals.gallery_initialized(gallery)
+   :noindex:
+
+   Called after the gallery is initialized.
+
+   :param gallery: the :class:`Gallery` object.
+
+.. data:: sigal.signals.media_initialized(media)
+   :noindex:
+
+   Called after the :class:`~sigal.gallery.Media`
+   (:class:`~sigal.gallery.Image` or :class:`~sigal.gallery.Video`) is
+   initialized.
+
+   :param media: the media object.
+
+.. data:: sigal.signals.gallery_build(gallery)
+   :noindex:
+
+   Called after the gallery is build (after media are resized and html files
+   are written).
+
+   :param gallery: the :class:`Gallery` object.
+
+.. data:: sigal.signals.img_resized(img, settings=settings)
+   :noindex:
+
+   Called after the image is resized. This signal work differently, the
+   modified image object must be returned by the registered funtion.
+
+   :param img: the PIL image object.
+   :param settings: the settings dict.
+
+List of plugins
+---------------
+
+Adjust plugin
+=============
+
+.. automodule:: sigal.plugins.adjust
+
+Copyright plugin
+================
+
+.. automodule:: sigal.plugins.copyright
diff --git a/requirements.txt b/requirements.txt
index adea3ff..67de39d 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,5 @@
 argh
+blinker
 Jinja2
 Markdown
 Pillow
diff --git a/setup.py b/setup.py
index 664373f..cc3277d 100644
--- a/setup.py
+++ b/setup.py
@@ -3,7 +3,7 @@
 import os
 from setuptools import setup
 
-requires = ['argh', 'jinja2', 'Markdown', 'Pillow', 'pilkit']
+requires = ['argh', 'blinker', 'jinja2', 'Markdown', 'Pillow', 'pilkit']
 
 entry_points = {
     'console_scripts': ['sigal = sigal:main']
diff --git a/sigal/__init__.py b/sigal/__init__.py
index 70030fe..d94d0ea 100644
--- a/sigal/__init__.py
+++ b/sigal/__init__.py
@@ -28,10 +28,12 @@ sigal is yet another python script to prepare a static gallery of images:
 
 * resize images, create thumbnails with some options (squared thumbs, ...).
 * generate html pages.
+
 """
 
 from __future__ import absolute_import, print_function
 
+import importlib
 import io
 import locale
 import logging
@@ -41,6 +43,7 @@ import time
 
 from argh import ArghParser, arg
 
+from .compat import server, socketserver, string_types
 from .gallery import Gallery
 from .log import init_logging
 from .pkgmeta import __version__
@@ -105,6 +108,8 @@ def build(source, destination, debug=False, verbose=False, force=False,
         sys.exit(1)
 
     locale.setlocale(locale.LC_ALL, settings['locale'])
+    init_plugins(settings)
+
     gal = Gallery(settings, theme=theme, ncpu=ncpu)
     gal.build(force=force)
 
@@ -120,14 +125,36 @@ def build(source, destination, debug=False, verbose=False, force=False,
            'seconds.').format(duration=time.time() - start_time, **gal.stats))
 
 
+def init_plugins(settings):
+    """Load plugins and call register()."""
+
+    logger = logging.getLogger(__name__)
+    logger.debug('Plugin paths: %s', settings['plugin_paths'])
+
+    for path in settings['plugin_paths']:
+        sys.path.insert(0, path)
+
+    for plugin in settings['plugins']:
+        try:
+            if isinstance(plugin, string_types):
+                mod = importlib.import_module(plugin)
+                mod.register(settings)
+            else:
+                plugin.register(settings)
+            logger.debug('Registered plugin %s', plugin)
+        except Exception as e:
+            logger.error('Failed to load plugin %s: %r', plugin, e)
+
+    for path in settings['plugin_paths']:
+        sys.path.remove(path)
+
+
 @arg('path', nargs='?', default='_build',
      help='Directory to serve (default: _build/)')
 def serve(path):
     """Run a simple web server."""
 
     if os.path.exists(path):
-        from .compat import server, socketserver
-
         os.chdir(path)
         PORT = 8000
         Handler = server.SimpleHTTPRequestHandler
diff --git a/sigal/gallery.py b/sigal/gallery.py
index a729642..6047a94 100644
--- a/sigal/gallery.py
+++ b/sigal/gallery.py
@@ -37,7 +37,7 @@ from datetime import datetime
 from os.path import isfile, join, splitext
 from PIL import Image as PILImage
 
-from . import image, video
+from . import image, video, signals
 from .compat import UnicodeMixin, strxfrm, url_quote
 from .image import process_image, get_exif_tags
 from .log import colored, BLUE
@@ -80,6 +80,7 @@ class Media(UnicodeMixin):
         self.raw_exif = None
         self.exif = None
         self.date = None
+        signals.media_initialized.send(self)
 
     def __repr__(self):
         return "<%s>(%r)" % (self.__class__.__name__, str(self))
@@ -221,6 +222,8 @@ class Album(UnicodeMixin):
 
             medias.sort(key=key, reverse=settings['medias_sort_reverse'])
 
+        signals.album_initialized.send(self)
+
     def __repr__(self):
         return "<%s>(path=%r, title=%r)" % (self.__class__.__name__, self.path,
                                             self.title)
@@ -458,6 +461,7 @@ class Gallery(object):
                 albums[relpath] = album
 
         self.logger.debug('Albums:\n%r', albums.values())
+        signals.gallery_initialized.send(self)
 
     def init_pool(self, ncpu):
         try:
@@ -527,6 +531,8 @@ class Gallery(object):
             for album in self.albums.values():
                 self.writer.write(album)
 
+        signals.gallery_build.send(self)
+
     def process_dir(self, album, force=False):
         """Process a list of images in a directory."""
 
diff --git a/sigal/image.py b/sigal/image.py
index 8404eb9..a5bf1cc 100644
--- a/sigal/image.py
+++ b/sigal/image.py
@@ -38,11 +38,11 @@ from copy import deepcopy
 from datetime import datetime
 from PIL.ExifTags import TAGS, GPSTAGS
 from PIL import Image as PILImage
-from PIL import ImageDraw, ImageOps
-from pilkit.processors import Transpose, Adjust
+from PIL import ImageOps
+from pilkit.processors import Transpose
 from pilkit.utils import save_image
 
-from . import compat
+from . import compat, signals
 from .settings import get_thumb
 
 
@@ -97,11 +97,10 @@ def generate_image(source, outname, settings, options=None):
         processor = processor_cls(*settings['img_size'], upscale=False)
         img = processor.process(img)
 
-    # Adjust the image after resizing
-    img = Adjust(**settings['adjust_options']).process(img)
-
-    if settings['copyright']:
-        add_copyright(img, settings['copyright'])
+    # signal.send() does not work here as plugins can modify the image, so we
+    # iterate other the receivers to call them with the image.
+    for receiver in signals.img_resized.receivers_for(img):
+        img = receiver(img, settings=settings)
 
     outformat = img.format or original_format or 'JPEG'
     logger.debug(u'Save resized image to {0} ({1})'.format(outname, outformat))
@@ -152,13 +151,6 @@ def process_image(filepath, outpath, settings):
                            fit=settings['thumb_fit'], options=options)
 
 
-def add_copyright(img, text):
-    """Add a copyright to the image."""
-
-    draw = ImageDraw.Draw(img)
-    draw.text((5, img.size[1] - 15), '\xa9 ' + text)
-
-
 def _get_exif_data(filename):
     """Return a dict with EXIF data."""
 
diff --git a/sigal/plugins/__init__.py b/sigal/plugins/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/sigal/plugins/adjust.py b/sigal/plugins/adjust.py
new file mode 100644
index 0000000..eb6b0f5
--- /dev/null
+++ b/sigal/plugins/adjust.py
@@ -0,0 +1,34 @@
+# -*- coding: utf-8 -*-
+
+"""Plugin which adjust the image after resizing.
+
+Based on pilkit's Adjust_ processor.
+
+.. _Adjust: https://github.com/matthewwithanm/pilkit/blob/master/pilkit/processors/base.py#L19
+
+Settings::
+
+    adjust_options = {'color': 1.0,
+                      'brightness': 1.0,
+                      'contrast': 1.0,
+                      'sharpness': 1.0}
+
+"""
+
+import logging
+from sigal import signals
+from pilkit.processors import Adjust
+
+logger = logging.getLogger(__name__)
+
+
+def adjust(img, settings=None):
+    logger.debug('Adjust image %r', img)
+    return Adjust(**settings['adjust_options']).process(img)
+
+
+def register(settings):
+    if settings.get('adjust_options'):
+        signals.img_resized.connect(adjust)
+    else:
+        logger.warning('Adjust options are not set')
diff --git a/sigal/plugins/copyright.py b/sigal/plugins/copyright.py
new file mode 100644
index 0000000..5da08d0
--- /dev/null
+++ b/sigal/plugins/copyright.py
@@ -0,0 +1,31 @@
+# -*- coding: utf-8 -*-
+
+"""Plugin which add a copyright to the image.
+
+Settings:
+
+- ``copyright``: the copyright text.
+
+TODO: Add more settings (font, size, ...)
+
+"""
+
+import logging
+from PIL import ImageDraw
+from sigal import signals
+
+logger = logging.getLogger(__name__)
+
+
+def add_copyright(img, settings=None):
+    logger.debug('Adding copyright to %r', img)
+    draw = ImageDraw.Draw(img)
+    draw.text((5, img.size[1] - 15), settings['copyright'])
+    return img
+
+
+def register(settings):
+    if settings.get('copyright'):
+        signals.img_resized.connect(add_copyright)
+    else:
+        logger.warning('Copyright text is not set')
diff --git a/sigal/settings.py b/sigal/settings.py
index f413d63..ea3cf09 100644
--- a/sigal/settings.py
+++ b/sigal/settings.py
@@ -31,13 +31,10 @@ from .compat import PY2
 
 
 _DEFAULT_CONFIG = {
-    'adjust_options': {'color': 1.0, 'brightness': 1.0,
-                       'contrast': 1.0, 'sharpness': 1.0},
     'albums_sort_reverse': False,
     'autorotate_images': True,
     'colorbox_column_size': 4,
     'copy_exif_data': False,
-    'copyright': '',
     'destination': '_build',
     'files_to_copy': (),
     'google_analytics': '',
@@ -55,6 +52,8 @@ _DEFAULT_CONFIG = {
     'make_thumbs': True,
     'orig_dir': 'original',
     'orig_link': False,
+    'plugins': [],
+    'plugin_paths': [],
     'source': '',
     'theme': 'colorbox',
     'thumb_dir': 'thumbnails',
diff --git a/sigal/signals.py b/sigal/signals.py
new file mode 100644
index 0000000..c175d33
--- /dev/null
+++ b/sigal/signals.py
@@ -0,0 +1,10 @@
+# -*- coding: utf-8 -*-
+
+from blinker import signal
+
+img_resized = signal('img_resized')
+
+album_initialized = signal('album_initialized')
+gallery_initialized = signal('gallery_initialized')
+gallery_build = signal('gallery_build')
+media_initialized = signal('media_initialized')
diff --git a/sigal/templates/sigal.conf.py b/sigal/templates/sigal.conf.py
index 364a3ce..9bf8956 100644
--- a/sigal/templates/sigal.conf.py
+++ b/sigal/templates/sigal.conf.py
@@ -27,13 +27,6 @@ img_size = (800, 600)
 # - None: don't resize
 # img_processor = 'ResizeToFit'
 
-# Adjust the image after resizing it. A default value of 1.0 leaves the images
-# untouched.
-# adjust_options = {'color': 1.0,
-#                   'brightness': 1.0,
-#                   'contrast': 1.0,
-#                   'sharpness': 1.0}
-
 # Generate thumbnails
 # make_thumbs = True
 
@@ -104,9 +97,6 @@ ignore_files = []
 # links = [('Example link', 'http://example.org'),
 #          ('Another link', 'http://example.org')]
 
-# Add a copyright text on the image (default: '')
-# copyright = "An example copyright message"
-
 # Google Analytics tracking code (UA-xxxx-x)
 # google_analytics = ''
 
@@ -138,3 +128,17 @@ ignore_files = []
 # Then the image size must be adapted to fit the column size.
 # The default is 4 columns which gives 220px. 3 columns gives 160px.
 # colorbox_column_size = 4
+
+# --------
+# Plugins
+# --------
+
+# Add a copyright text on the image (default: '')
+# copyright = "© An example copyright message"
+
+# Adjust the image after resizing it. A default value of 1.0 leaves the images
+# untouched.
+# adjust_options = {'color': 1.0,
+#                   'brightness': 1.0,
+#                   'contrast': 1.0,
+#                   'sharpness': 1.0}
diff --git a/tests/sample/sigal.conf.py b/tests/sample/sigal.conf.py
index 348d0d5..ec6a44a 100644
--- a/tests/sample/sigal.conf.py
+++ b/tests/sample/sigal.conf.py
@@ -8,7 +8,11 @@ keep_orig = True
 links = [('Example link', 'http://example.org'),
          ('Another link', 'http://example.org')]
 
-copyright = "An example copyright message"
+from sigal.plugins import copyright
+plugins = ['sigal.plugins.adjust', copyright]
+copyright = u"© An example copyright message"
+adjust_options = {'color': 0.0, 'brightness': 1.0,
+                  'contrast': 1.0, 'sharpness': 0.0}
 
 # theme = 'galleria'
 # thumb_size = (280, 210)