From a63ebb3dd1f586f8d8bec85a31ec48a96d29ebc2 Mon Sep 17 00:00:00 2001
From: Nishida Daishiro <nishidadaishiro@team-lab.com>
Date: Wed, 28 May 2025 18:23:47 +0900
Subject: [PATCH] fix getUndistortRectangles to ignore corners

---
 modules/calib3d/src/calibration_base.cpp | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/modules/calib3d/src/calibration_base.cpp b/modules/calib3d/src/calibration_base.cpp
index f90a85a064..71836367e3 100644
--- a/modules/calib3d/src/calibration_base.cpp
+++ b/modules/calib3d/src/calibration_base.cpp
@@ -1527,7 +1527,7 @@ void cv::getUndistortRectangles(InputArray _cameraMatrix, InputArray _distCoeffs
 {
     const int N = 9;
     int x, y, k;
-    Mat _pts(1, 4*(N-1), CV_64FC2);
+    Mat _pts(1, 4*(N-2), CV_64FC2);
     Point2d* pts = _pts.ptr<Point2d>();
 
     // generate a grid of points across the image to estimate the distortion deformation
@@ -1543,6 +1543,12 @@ void cv::getUndistortRectangles(InputArray _cameraMatrix, InputArray _distCoeffs
                 // have no influence on the two deformation rectangles that are calculated below
                 continue;
             }
+            if ((x == 0 || x == N - 1) && (y == 0 || y == N - 1))
+            {
+                // skip corners, because undistortPoints is likely to fail and return the same
+                // value
+                continue;
+            }
             pts[k++] = Point2d(x * stepX, y * stepY);
         }
     }
@@ -1561,6 +1567,10 @@ void cv::getUndistortRectangles(InputArray _cameraMatrix, InputArray _distCoeffs
             {
                 continue;
             }
+            if ((x == 0 || x == N - 1) && (y == 0 || y == N - 1))
+            {
+                continue;
+            }
 
             Point2d p = pts[k++];
             oX0 = MIN(oX0, p.x);