Merge pull request #22798 from lamm45:distransform-large

Fix distransform to work with large images #22798

This attempts to fix the following bug which was caused by storing squares of large integers into 32-bit floating point variables:
https://github.com/opencv/opencv/issues/22732


### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [ ] The feature is well documented and sample code can be built with the project CMake

modules/imgproc/test/test_distancetransform.cpp

@@ -302,4 +302,46 @@ BIGDATA_TEST(Imgproc_DistanceTransform, large_image_12218)
     EXPECT_EQ(nz, (size.height*size.width / 2));
 }
 
+TEST(Imgproc_DistanceTransform, wide_image_22732)
+{
+    Mat src = Mat::zeros(1, 4099, CV_8U); // 4099 or larger used to be bad
+    Mat dist(src.rows, src.cols, CV_32F);
+    distanceTransform(src, dist, DIST_L2, DIST_MASK_PRECISE, CV_32F);
+    int nz = countNonZero(dist);
+    EXPECT_EQ(nz, 0);
+}
+
+TEST(Imgproc_DistanceTransform, large_square_22732)
+{
+    Mat src = Mat::zeros(8000, 8005, CV_8U), dist;
+    distanceTransform(src, dist, DIST_L2, DIST_MASK_PRECISE, CV_32F);
+    int nz = countNonZero(dist);
+    EXPECT_EQ(dist.size(), src.size());
+    EXPECT_EQ(dist.type(), CV_32F);
+    EXPECT_EQ(nz, 0);
+
+    Point p0(src.cols-1, src.rows-1);
+    src.setTo(1);
+    src.at<uchar>(p0) = 0;
+    distanceTransform(src, dist, DIST_L2, DIST_MASK_PRECISE, CV_32F);
+    EXPECT_EQ(dist.size(), src.size());
+    EXPECT_EQ(dist.type(), CV_32F);
+    bool first = true;
+    int nerrs = 0;
+    for (int y = 0; y < dist.rows; y++)
+        for (int x = 0; x < dist.cols; x++) {
+            float d = dist.at<float>(y, x);
+            double dx = (double)(x - p0.x), dy = (double)(y - p0.y);
+            float d0 = (float)sqrt(dx*dx + dy*dy);
+            if (std::abs(d0 - d) > 1) {
+                if (first) {
+                    printf("y=%d, x=%d. dist_ref=%.2f, dist=%.2f\n", y, x, d0, d);
+                    first = false;
+                }
+                nerrs++;
+            }
+        }
+    EXPECT_EQ(0, nerrs) << "reference distance map is different from computed one at " << nerrs << " pixels\n";
+}
+
 }} // namespace