--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/core/images/utils.py	Tue Sep 22 20:23:50 2015 -0500
@@ -0,0 +1,118 @@
+"""
+This file contains common utility functions for manipulating images for
+the rest of the applications in the project.
+"""
+from PIL import ImageFile
+from PIL import Image
+
+
+def parse_image(file):
+    """
+    Returns a PIL Image from the supplied Django file object.
+    Throws IOError if the file does not parse as an image file or some other
+    I/O error occurred.
+
+    """
+    parser = ImageFile.Parser()
+    for chunk in file.chunks():
+        parser.feed(chunk)
+    image = parser.close()
+    return image
+
+
+def downscale_image_square(image, size):
+    """
+    Scale an image to the square dimensions given by size (in pixels).
+    The new image is returned.
+    If the image is already smaller than (size, size) then no scaling
+    is performed and the image is returned unchanged.
+
+    """
+    # don't upscale
+    if (size, size) >= image.size:
+        return image
+
+    (w, h) = image.size
+    if w > h:
+        diff = (w - h) / 2
+        image = image.crop((diff, 0, w - diff, h))
+    elif h > w:
+        diff = (h - w) / 2
+        image = image.crop((0, diff, w, h - diff))
+    image = image.resize((size, size), Image.ANTIALIAS)
+    return image
+
+
+# Various image transformation functions:
+def flip_horizontal(im):
+    return im.transpose(Image.FLIP_LEFT_RIGHT)
+
+def flip_vertical(im):
+    return im.transpose(Image.FLIP_TOP_BOTTOM)
+
+def rotate_180(im):
+    return im.transpose(Image.ROTATE_180)
+
+def rotate_90(im):
+    return im.transpose(Image.ROTATE_90)
+
+def rotate_270(im):
+    return im.transpose(Image.ROTATE_270)
+
+def transpose(im):
+    return rotate_90(flip_horizontal(im))
+
+def transverse(im):
+    return rotate_90(flip_vertical(im))
+
+# From http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/EXIF.html
+# EXIF Orientation tag values:
+# 1 = Horizontal (normal)
+# 2 = Mirror horizontal
+# 3 = Rotate 180
+# 4 = Mirror vertical
+# 5 = Mirror horizontal and rotate 270 CW
+# 6 = Rotate 90 CW
+# 7 = Mirror horizontal and rotate 90 CW
+# 8 = Rotate 270 CW
+
+ORIENT_FUNCS = {
+    2: flip_horizontal,
+    3: rotate_180,
+    4: flip_vertical,
+    5: transpose,
+    6: rotate_270,
+    7: transverse,
+    8: rotate_90,
+}
+
+ORIENT_TAG = 0x112
+
+
+def orient_image(im):
+    """Transforms the given image according to embedded EXIF data.
+
+    The image instance, im, should be a PIL Image.
+    If there is EXIF information for the image, and the orientation tag
+    indicates that the image should be transformed, perform the transformation.
+
+    Returns a tuple of the form (flag, image) where flag is True if the image
+    was oriented and False otherwise. image is either a new transformed image or
+    the original image instance.
+
+    """
+    if hasattr(im, '_getexif'):
+        try:
+            exif = im._getexif()
+        except IndexError:
+            # Work around issue seen in Pillow
+            # https://github.com/python-pillow/Pillow/issues/518
+            exif = None
+
+        if exif and ORIENT_TAG in exif:
+            orientation = exif[ORIENT_TAG]
+            func = ORIENT_FUNCS.get(orientation)
+            if func:
+                return (True, func(im))
+
+    return (False, im)