Add in ability to validate images and image paths (urls)

common/lib/xmodule/xmodule/open_ended_image_submission.py

 from PIL import Image
+import urlparse
 
 TRUSTED_IMAGE_DOMAINS = [
     'wikipedia.com',
@@ -6,6 +7,12 @@ TRUSTED_IMAGE_DOMAINS = [
     'wikipedia.org'
 ]
 
+ALLOWABLE_IMAGE_SUFFIXES = [
+    'jpg',
+    'png',
+    'gif'
+]
+
 MAX_IMAGE_DIM = 150
 MAX_COLORS_TO_COUNT = 16
 MAX_COLORS = 5
@@ -25,5 +32,56 @@ class ImageProperties(object):
         else:
             colors = len(colors)
 
-        
+        return colors <= MAX_COLORS
+
+    def get_skin_ratio(self):
+        im = self.image
+        skin = sum([count for count, rgb in im.getcolors(im.size[0]*im.size[1]) if rgb[0]>60 and rgb[1]<(rgb[0]*0.85) and rgb[2]<(rgb[0]*0.7) and rgb[1]>(rgb[0]*0.4) and rgb[2]>(rgb[0]*0.2)])
+        bad_color_val =  float(skin)/float(im.size[0]*im.size[1])
+        if bad_color_val > .4:
+            is_okay = False
+        else:
+            is_okay = True
+        return is_okay
+
+    def run_tests(self):
+        image_is_okay = self.count_colors() and self.get_skin_ratio()
+        return image_is_okay
+
+class URLProperties(object):
+    def __init__(self, url_string):
+        self.url_string = url_string
+
+    def check_if_parses(self):
+        success = False
+        try:
+            self.parsed_url = urlparse.urlparse(url_string)
+            success = True
+        except:
+            pass
+
+        return success
+
+    def check_suffix(self):
+        good_suffix = False
+        for suffix in ALLOWABLE_IMAGE_SUFFIXES:
+            if self.url_string.endswith(suffix)
+            good_suffix = True
+            break
+        return good_suffix
+
+    def run_tests(self):
+        url_is_okay = self.check_suffix() and self.check_if_parses()
+        return url_is_okay
+
+def run_url_tests(url_string):
+    url_properties = URLProperties(url_string)
+    return url_properties.run_tests()
+
+def run_image_tests(image):
+    image_properties = ImageProperties(image)
+    return image_properties.run_tests()
+
+
+