improve transformation: vertical points is better than corners

lines.cpp

@@ -256,8 +256,9 @@ BookShape get_book_shape(cv::Mat img)
 	cv::Point middle2 = further_point_from_line(get_line(corn_3, corn_4), points1);
 
 	BookShape bs = BookShape(
-			corn_1, middle1, corn_2,
-			corn_4, middle2, corn_3);
+			vertical_points[1][vertical_points[1].size()-1], middle1, vertical_points[0][0],
+			vertical_points[1][0], middle2, vertical_points[0][vertical_points[0].size()-1]
+			);
 	return bs;
 }