Add custom dimension picture function

lib/facebook.ex

@@ -318,6 +318,26 @@ defmodule Facebook do
       |> ResponseFormatter.format_response
   end
 
+  @doc """
+  A Picture for a Facebook User with custom dimensions
+
+  ## Example
+      iex> Facebook.picture("<Some Id>", 480, 480, "<Access Token>")
+      {:ok, %{"data": "..."}}
+
+  See: https://developers.facebook.com/docs/graph-api/reference/user/picture/
+  """
+  @spec picture(page_id, width :: integer, height :: integer, access_token) :: resp
+  def picture(page_id, width, height, access_token) do
+    params = [width: width, height: height, redirect: false]
+             |> add_app_secret(access_token)
+             |> add_access_token(access_token)
+
+    ~s(/#{page_id}/picture)
+      |> GraphAPI.get([], params: params)
+      |> ResponseFormatter.format_response
+  end
+
   @doc """
   Likes of the currently logged in user specified by the `t:access_token/0`
 

test/facebook_test.exs

@@ -94,13 +94,36 @@ defmodule FacebookTest do
       end
     end
 
+    test "success with custom dimensions", %{id: id, access_token: access_token} do
+      with_mock :hackney, GraphMock.mock_options(
+        fn(_) -> GraphMock.picture(:success) end
+      ) do
+        {:ok, %{"data" => picture_data}} = Facebook.picture(
+          id,
+          320,
+          320,
+          access_token
+        )
+
+        assert(String.length(picture_data["url"]) > 0)
+      end
+    end
+
     test "error", %{id: id, invalid_access_token: invalid_access_token} do
       with_mock :hackney, GraphMock.mock_options(
         fn(_) -> GraphMock.error() end
       ) do
         assert {:error, _} = Facebook.picture(id, "small", invalid_access_token)
       end
     end
+
+    test "error with custom dimensions", %{id: id, invalid_access_token: invalid_access_token} do
+      with_mock :hackney, GraphMock.mock_options(
+        fn(_) -> GraphMock.error() end
+      ) do
+        assert {:error, _} = Facebook.picture(id, 320, 320, invalid_access_token)
+      end
+    end
   end
 
   describe "publish" do