FEATURE: new 'min ratio to crop' site setting

config/locales/server.en.yml

@@ -1342,6 +1342,8 @@ en:
 
     strip_image_metadata: "Strip image metadata."
 
+    min_ratio_to_crop: "Ratio used to crop tall images. Enter the result of width / height."
+
     enable_flash_video_onebox: "Enable embedding of swf and flv (Adobe Flash) links in oneboxes. WARNING: may introduce security risks."
 
     default_invitee_trust_level: "Default trust level (0-4) for invited users."

config/site_settings.yml

@@ -941,6 +941,11 @@ files:
     default: true
     client: true
   strip_image_metadata: true
+  min_ratio_to_crop:
+    type: float
+    default: 0.45 # 90% of 18:9
+    min: 0
+    max: 1
 
 trust:
   default_trust_level:

lib/cooked_post_processor.rb

@@ -267,10 +267,6 @@ class CookedPostProcessor
   rescue URI::InvalidURIError
   end
 
-  # only crop when the image is taller than 18:9
-  # we only use 90% of that to allow for a small margin
-  MIN_RATIO_TO_CROP ||= (9.0 / 18.0) * 0.9
-
   def convert_to_link!(img)
     src = img["src"]
     return if src.blank? || is_a_hyperlink?(img)
@@ -288,7 +284,10 @@ class CookedPostProcessor
     return if original_width <= width && original_height <= height
     return if original_width <= SiteSetting.max_image_width && original_height <= SiteSetting.max_image_height
 
-    if crop = (original_width.to_f / original_height.to_f < MIN_RATIO_TO_CROP)
+    crop   = SiteSetting.min_ratio_to_crop > 0
+    crop &&= original_width.to_f / original_height.to_f < SiteSetting.min_ratio_to_crop
+
+    if crop
       width, height = ImageSizer.crop(original_width, original_height)
       img["width"] = width
       img["height"] = height