From bbd345ce0b34fc255a8c09e30f8fe83b398ee3ec Mon Sep 17 00:00:00 2001
From: Stephan Jaekel <steph@rdev.info>
Date: Mon, 13 Mar 2017 14:14:05 +0100
Subject: [PATCH] Refactor thumbnail tag, moved logic from tag to new
 ThumbnailSet class. Fixes #6.

---
 .../templatetags/ultimatethumb_tags.py        | 35 ++-----------
 ultimatethumb/thumbnail.py                    | 51 ++++++++++++++++++-
 2 files changed, 53 insertions(+), 33 deletions(-)

diff --git a/ultimatethumb/templatetags/ultimatethumb_tags.py b/ultimatethumb/templatetags/ultimatethumb_tags.py
index 7d0ae22..aae6ca8 100644
--- a/ultimatethumb/templatetags/ultimatethumb_tags.py
+++ b/ultimatethumb/templatetags/ultimatethumb_tags.py
@@ -2,8 +2,8 @@
 
 from django.template import Library
 
-from ..thumbnail import Thumbnail
-from ..utils import get_size_for_path, parse_sizes, parse_source
+from ..thumbnail import ThumbnailSet
+from ..utils import parse_source
 
 
 VALID_IMAGE_FILE_EXTENSIONS = ('jpg', 'jpeg', 'png', 'gif', 'ico')
@@ -34,7 +34,7 @@ def ultimatethumb(
         context[as_var] = None
         return ''
 
-    thumbnail_options = {'upscale': upscale}
+    thumbnail_options = {'upscale': upscale, 'factor2x': retina}
 
     if crop is not None:
         thumbnail_options['crop'] = crop
@@ -45,31 +45,4 @@ def ultimatethumb(
     if pngquant is not None:
         thumbnail_options['pngquant'] = pngquant
 
-    source_size = get_size_for_path(source)
-
-    # If retina option is enabled, pretend that the source is half as large as
-    # it is. We do this to ensure that we have "retina" images which effectively
-    # are doubled in size. Doing this, we never have to upscale the image.
-    if retina:
-        source_size = (int(source_size[0] / 2), int(source_size[1] / 2))
-    else:
-        thumbnail_options['factor2x'] = False
-
-    thumbnails = []
-
-    oversize = False
-    for size in parse_sizes(sizes):
-        if '%' not in size[0] and not upscale:
-            if int(size[0]) > source_size[0] or int(size[1]) > source_size[1]:
-                size = [str(source_size[0]), str(source_size[1])]
-                oversize = True
-
-        options = {'size': size}
-        options.update(thumbnail_options)
-        thumbnails.append(Thumbnail(source, options))
-
-        if oversize:
-            break
-
-    context[as_var] = thumbnails
-    return ''
+    context[as_var] = ThumbnailSet(source, sizes, thumbnail_options).thumbnails
diff --git a/ultimatethumb/thumbnail.py b/ultimatethumb/thumbnail.py
index b2e09cd..48382e8 100644
--- a/ultimatethumb/thumbnail.py
+++ b/ultimatethumb/thumbnail.py
@@ -4,10 +4,12 @@
 from barbeque.commands.imaging import GmConvertCommand
 from barbeque.files import MoveableNamedTemporaryFile
 from django.conf import settings
+from django.utils.functional import cached_property
 
 from .commands import PngquantCommand
 from .storage import thumbnail_storage
-from .utils import build_url, factor_size, get_size_for_path, get_thumb_data, get_thumb_name
+from .utils import (
+    build_url, factor_size, get_size_for_path, get_thumb_data, get_thumb_name, parse_sizes)
 
 
 CROP_GRAVITY = {
@@ -37,6 +39,51 @@
 Size = namedtuple('Size', ('width', 'height'))
 
 
+class ThumbnailSet(object):
+
+    def __init__(self, source, sizes, options):
+        self.source = source
+        self.sizes = sizes
+        self.options = options
+
+    @cached_property
+    def thumbnails(self):
+        return self.get_thumbnails()
+
+    def get_source_size(self):
+        # If retina option is enabled, pretend that the source is half as large as
+        # it is. We do this to ensure that we have "retina" images which effectively
+        # are doubled in size. Doing this, we never have to upscale the image.
+        source_size = get_size_for_path(self.source)
+        if self.options.get('factor2x', True):
+            source_size = int(source_size[0] / 2), int(source_size[1] / 2)
+
+        return source_size
+
+    def get_sizes(self):
+        return parse_sizes(self.sizes)
+
+    def get_thumbnails(self):
+        thumbnails = []
+        source_size = self.get_source_size()
+
+        oversize = False
+        for size in self.get_sizes():
+            if '%' not in size[0] and not self.options.get('upscale', False):
+                if int(size[0]) > source_size[0] or int(size[1]) > source_size[1]:
+                    size = [str(source_size[0]), str(source_size[1])]
+                    oversize = True
+
+            options = {'size': size}
+            options.update(self.options)
+            thumbnails.append(Thumbnail(self.source, options))
+
+            if oversize:
+                break
+
+        return thumbnails
+
+
 class Thumbnail(object):
 
     def __init__(self, source, opts):
@@ -67,7 +114,7 @@ def from_name(cls, name):
     def get_name(self):
         return get_thumb_name(self.source, **self.options)
 
-    @property
+    @cached_property
     def size(self):
         return self.get_estimated_size()