Add a plugin system with blinker, and make plugins for copyright and adjust.

docs/index.rst

@@ -11,4 +11,5 @@ Documentation
    configuration
    album_information
    themes
+   plugins
    changelog

docs/plugins.rst

@@ -0,0 +1,29 @@
+=========
+ Plugins
+=========
+
+Signals
+-------
+
+.. data:: sigal.signals.img_resized
+   :noindex:
+
+   Called after the image is resized.
+
+Write a new plugin
+------------------
+
+See an example with the copyright plugin:
+
+.. literalinclude:: ../sigal/plugins/copyright.py
+   :language: python
+
+Adjust plugin
+-------------
+
+.. automodule:: sigal.plugins.adjust
+
+Copyright plugin
+----------------
+
+.. automodule:: sigal.plugins.copyright

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

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."""
 

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')

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')

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',

sigal/signals.py

@@ -0,0 +1,5 @@
+# -*- coding: utf-8 -*-
+
+from blinker import signal
+
+img_resized = signal('img_resized')