diff --git a/libheif/box.h b/libheif/box.h
index 8a510525fc..3fcc8e3da2 100644
--- a/libheif/box.h
+++ b/libheif/box.h
@@ -1059,16 +1059,16 @@ class Box_cmin : public FullBox
       principal_point_y -= clap->top(image_height);
     }
 
-    void apply_imir(const Box_imir* imir) {
+    void apply_imir(const Box_imir* imir, int image_width, int image_height) {
       switch (imir->get_mirror_direction()) {
         case heif_transform_mirror_direction_horizontal:
           focal_length_x *= -1;
           skew *= -1;
-          principal_point_x *= -1;
+          principal_point_x = image_width - 1 - principal_point_x;
           break;
         case heif_transform_mirror_direction_vertical:
           focal_length_y *= -1;
-          principal_point_y *= -1;
+          principal_point_y = image_height - 1 - principal_point_y;
           break;
         case heif_transform_mirror_direction_invalid:
           break;
diff --git a/libheif/context.cc b/libheif/context.cc
index 8ab3fa6330..3eadfa12d5 100644
--- a/libheif/context.cc
+++ b/libheif/context.cc
@@ -650,7 +650,7 @@ Error HeifContext::interpret_heif_file()
 
       auto imir = std::dynamic_pointer_cast<Box_imir>(prop);
       if (imir) {
-        image->get_intrinsic_matrix().apply_imir(imir.get());
+        image->get_intrinsic_matrix().apply_imir(imir.get(), image->get_width(), image->get_height());
       }
 
       auto irot = std::dynamic_pointer_cast<Box_irot>(prop);