diff --git a/shard.lock b/shard.lock
index 10cf827..3476d56 100644
--- a/shard.lock
+++ b/shard.lock
@@ -32,6 +32,10 @@ shards:
     github: mamantoha/http_proxy
     version: 0.7.1
 
+  image_size:
+    github: hkalexling/image_size.cr
+    version: 0.1.1
+
   kemal:
     github: kemalcr/kemal
     version: 0.26.1
diff --git a/shard.yml b/shard.yml
index 3563d7a..8e9dd71 100644
--- a/shard.yml
+++ b/shard.yml
@@ -34,3 +34,5 @@ dependencies:
     github: kostya/myhtml
   http_proxy:
     github: mamantoha/http_proxy
+  image_size:
+   github: hkalexling/image_size.cr
diff --git a/src/library/entry.cr b/src/library/entry.cr
index ba4b84a..1f06e70 100644
--- a/src/library/entry.cr
+++ b/src/library/entry.cr
@@ -1,3 +1,5 @@
+require "image_size"
+
 class Entry
   property zip_path : String, book : Title, title : String,
     size : String, pages : Int32, id : String, encoded_path : String,
@@ -99,6 +101,31 @@ class Entry
     img
   end
 
+  def page_aspect_ratios
+    ratios = [] of Float64
+    ArchiveFile.open @zip_path do |file|
+      file.entries
+        .select { |e|
+          SUPPORTED_IMG_TYPES.includes? \
+            MIME.from_filename? e.filename
+        }
+        .sort { |a, b|
+          compare_numerically a.filename, b.filename
+        }
+        .each_with_index do |e, i|
+          begin
+            data = file.read_entry(e).not_nil!
+            size = ImageSize.get data
+            ratios << size.height / size.width
+          rescue
+            Logger.warn "Failed to read page #{i} of entry #{@id}"
+            ratios << 1_f64
+          end
+        end
+    end
+    ratios
+  end
+
   def next_entry(username)
     entries = @book.sorted_entries username
     idx = entries.index self
diff --git a/src/routes/api.cr b/src/routes/api.cr
index a6fb51a..b8bd5db 100644
--- a/src/routes/api.cr
+++ b/src/routes/api.cr
@@ -332,5 +332,28 @@ class APIRouter < Router
         }.to_json
       end
     end
+
+    get "/api/ratios/:tid/:eid" do |env|
+      begin
+        tid = env.params.url["tid"]
+        eid = env.params.url["eid"]
+
+        title = @context.library.get_title tid
+        raise "Title ID `#{tid}` not found" if title.nil?
+        entry = title.get_entry eid
+        raise "Entry ID `#{eid}` of `#{title.title}` not found" if entry.nil?
+
+        ratios = entry.page_aspect_ratios
+        send_json env, {
+          "success" => true,
+          "ratios"  => ratios,
+        }.to_json
+      rescue e
+        send_json env, {
+          "success" => false,
+          "error"   => e.message,
+        }.to_json
+      end
+    end
   end
 end