Only load Image once when creating all three Thumbnail sizes.

django_images/utils.py

@@ -1,13 +1,45 @@
+from contextlib import contextmanager
+from io import BytesIO
+import PIL
 from PIL import Image
 
 
+@contextmanager
+def open_django_file(fieldfile):
+    fieldfile.open()
+    try:
+        yield fieldfile
+    finally:
+        fieldfile.close()
+
+
+def scale_and_crop_iter(image, options):
+    """
+    Generator which will yield several variations on the input image.
+    Resize, crop and/or change quality of image.
+
+    :param image: Source image file
+    :param type: :class:`django.core.files.images.ImageFile
+
+    :param`options: List of option dictionaries, See scale_and_crop_single
+    argument names for available keys.
+    :type options: list of dict
+    """
+    with open_django_file(image) as img:
+        im = Image.open(img)
+        im.load()
+        for opts in options:
+            # Use already-loaded file when cropping.
+            yield scale_and_crop_single(im, **opts)
+
+
 # this neat function is based on easy-thumbnails
-def scale_and_crop(image, size, crop=False, upscale=False, quality=None):
+def scale_and_crop_single(image, size, crop=False, upscale=False, quality=None):
     """
     Resize, crop and/or change quality of an image.
 
     :param image: Source image file
-    :param type: :class:`django.core.files.images.ImageFile`
+    :param type: :class:`PIL.Image`
 
     :param size: Size as width & height, zero as either means unrestricted
     :type size: tuple of two int
@@ -24,15 +56,7 @@ def scale_and_crop(image, size, crop=False, upscale=False, quality=None):
     :return: Handled image
     :rtype: class:`PIL.Image`
     """
-    # Open image and store format/metadata.
-    image.open()
-    im = Image.open(image)
-    im_format, im_info = im.format, im.info
-    if quality:
-        im_info['quality'] = quality
-
-    # Force PIL to load image data.
-    im.load()
+    im = image
 
     source_x, source_y = [float(v) for v in im.size]
     target_x, target_y = [float(v) for v in size]
@@ -68,6 +92,31 @@ def scale_and_crop(image, size, crop=False, upscale=False, quality=None):
             im = im.crop(box)
 
     # Close image and replace format/metadata, as PIL blows this away.
-    im.format, im.info = im_format, im_info
-    image.close()
+    # We mutate the quality, but needs to passed into save() to actually
+    # do anything.
+    info = image.info
+    if quality is not None:
+        info['quality'] = quality
+    im.format, im.info = image.format, info
     return im
+
+
+def write_image_in_memory(img):
+    # save to memory
+    buf = BytesIO()
+    try:
+        img.save(buf, img.format, **img.info)
+    except IOError:
+        if img.info.get('progression'):
+            orig_MAXBLOCK = PIL.ImageFile.MAXBLOCK
+            temp_MAXBLOCK = 1048576
+            if orig_MAXBLOCK >= temp_MAXBLOCK:
+                raise
+            PIL.ImageFile.MAXBLOCK = temp_MAXBLOCK
+            try:
+                img.save(buf, img.format, **img.info)
+            finally:
+                PIL.ImageFile.MAXBLOCK = orig_MAXBLOCK
+        else:
+            raise
+    return buf