Merge pull request #27001 from DanBmh/opt_newoptcm

asmorkalov · web-flow · commit 6fb082ae7f06 · 2025-03-11T12:47:35.000+03:00
Optimize camera matrix undistortion
diff --git a/modules/calib3d/src/calibration_base.cpp b/modules/calib3d/src/calibration_base.cpp
@@ -1527,12 +1527,25 @@ void cv::getUndistortRectangles(InputArray _cameraMatrix, InputArray _distCoeffs
 {
     const int N = 9;
     int x, y, k;
-    Mat _pts(1, N*N, CV_64FC2);
+    Mat _pts(1, 4*(N-1), CV_64FC2);
     Point2d* pts = _pts.ptr<Point2d>();
 
+    // generate a grid of points across the image to estimate the distortion deformation
+    double stepX = (imgSize.width - 1) / static_cast<double>(N - 1);
+    double stepY = (imgSize.height - 1) / static_cast<double>(N - 1);
     for( y = k = 0; y < N; y++ )
+    {
         for( x = 0; x < N; x++ )
-            pts[k++] = Point2d((double)x*(imgSize.width-1)/(N-1), (double)y*(imgSize.height-1)/(N-1));
+        {
+            if (x != 0 && x != N - 1 && y != 0 && y != N - 1)
+            {
+                // skip all points except those on the image border, because inner grid points
+                // have no influence on the two deformation rectangles that are calculated below
+                continue;
+            }
+            pts[k++] = Point2d(x * stepX, y * stepY);
+        }
+    }
 
     undistortPoints(_pts, _pts, _cameraMatrix, _distCoeffs, R, newCameraMatrix);
 
@@ -1541,8 +1554,14 @@ void cv::getUndistortRectangles(InputArray _cameraMatrix, InputArray _distCoeffs
     // find the inscribed rectangle.
     // the code will likely not work with extreme rotation matrices (R) (>45%)
     for( y = k = 0; y < N; y++ )
+    {
         for( x = 0; x < N; x++ )
         {
+            if (x != 0 && x != N - 1 && y != 0 && y != N - 1)
+            {
+                continue;
+            }
+
             Point2d p = pts[k++];
             oX0 = MIN(oX0, p.x);
             oX1 = MAX(oX1, p.x);
@@ -1558,6 +1577,7 @@ void cv::getUndistortRectangles(InputArray _cameraMatrix, InputArray _distCoeffs
             if( y == N-1 )
                 iY1 = MIN(iY1, p.y);
         }
+    }
     inner = Rect_<double>(iX0, iY0, iX1-iX0, iY1-iY0);
     outer = Rect_<double>(oX0, oY0, oX1-oX0, oY1-oY0);
 }
