Add config option for tweaking how thumbnails should be cropped

sigal/image.py

@@ -131,15 +131,15 @@ def generate_image(source, outname, settings, options=None):
     save_image(img, outname, outformat, options=options, autoconvert=True)
 
 
-def generate_thumbnail(source, outname, box, delay, fit=True, options=None):
+def generate_thumbnail(source, outname, box, delay, fit=True, options=None, thumb_fit_centering=(0.5, 0.5)):
     """Create a thumbnail image."""
 
     logger = logging.getLogger(__name__)
     img = _read_image(source)
     original_format = img.format
 
     if fit:
-        img = ImageOps.fit(img, box, PILImage.ANTIALIAS)
+        img = ImageOps.fit(img, box, PILImage.ANTIALIAS, centering=thumb_fit_centering)
     else:
         img.thumbnail(box, PILImage.ANTIALIAS)
 
@@ -171,7 +171,8 @@ def process_image(filepath, outpath, settings):
             thumb_name = os.path.join(outpath, get_thumb(settings, filename))
             generate_thumbnail(outname, thumb_name, settings['thumb_size'],
                                settings['thumb_video_delay'],
-                               fit=settings['thumb_fit'], options=options)
+                               fit=settings['thumb_fit'], options=options,
+                               thumb_fit_centering=settings["thumb_fit_centering"])
     except Exception as e:
         logger.info('Failed to process: %r', e)
         if logger.getEffectiveLevel() == logging.DEBUG:

sigal/settings.py

@@ -66,6 +66,7 @@
     'theme': 'colorbox',
     'thumb_dir': 'thumbnails',
     'thumb_fit': True,
+    'thumb_fit_centering': (0.5, 0.5),
     'thumb_prefix': '',
     'thumb_size': (200, 150),
     'thumb_suffix': '',

sigal/templates/sigal.conf.py

@@ -93,6 +93,11 @@
 # Crop the image to fill the box
 # thumb_fit = True
 
+# When using thumb_fit, specifies what we should crop
+# for usage see
+# http://pillow.readthedocs.io/en/3.1.x/reference/ImageOps.html#PIL.ImageOps.fit
+# thumb_fit_centering = (0.5, 0.5)
+
 # Delay in seconds to avoid black thumbnails in videos with fade-in
 # thumb_video_delay = '0'