imgproc: don’t use ippiCopySubpixIntersect for windows crossing the image border - #30363

hal/ipp/src/samplers_ipp.cpp

@@ -21,6 +21,24 @@ int ipp_hal_getRectSubPix(int src_type, const uchar* src_data, size_t src_step,
 
     int ddepth = CV_MAT_DEPTH(patch_type);
 
+    // ippiCopySubpixIntersect replicates the border incorrectly in some cases, see
+    // https://github.com/opencv/opencv/issues/30301. The window position is computed the same way as IPP does,
+    // including (int)(x + w) - w, which is not equal to cvFloor() for some inputs.
+    float fx = (float)center_x - 0.5f * (patch_width - 1);
+    float fy = (float)center_y - 0.5f * (patch_height - 1);
+    int sx = (int)(fx + patch_width) - patch_width;
+    int sy = (int)(fy + patch_height) - patch_height;
+
+    // the window crosses the top edge and reaches the last column: the top rows get src(0, cols-2)
+    // instead of src(0, cols-1), and for 1-column images IPP reads outside of the image
+    if( sy < 0 && sx >= src_width - patch_width )
+        return CV_HAL_ERROR_NOT_IMPLEMENTED;
+
+
+    // 8u->8u, the window lies totally to the left of the image: the fixed-point weights overflow
+    if( src_type == CV_8UC1 && ddepth == CV_8U && fx + patch_width < 0 )
+        return CV_HAL_ERROR_NOT_IMPLEMENTED;
+
     typedef IppStatus (CV_STDCALL *ippiGetRectSubPixFunc)( const void* src, int src_step,
                                                            IppiSize src_size, void* dst,
                                                            int dst_step, IppiSize win_size,

modules/imgproc/test/test_imgwarp.cpp

@@ -1386,5 +1386,45 @@ TEST(Imgproc_ConvertMaps, regression_22763)
     EXPECT_EQ(CV_16UC1, dst2.type());
 }
 
+// https://github.com/opencv/opencv/issues/30301
+typedef testing::TestWithParam<testing::tuple<int, int> > Imgproc_GetRectSubPix_Border;
+
+TEST_P(Imgproc_GetRectSubPix_Border, regression_30301)
+{
+    const int depth = get<0>(GetParam()), ddepth = get<1>(GetParam());
+
+    // The images are ROIs of a buffer filled with 250, so reads outside of them show up in the result
+    const Rect rampRoi(8, 8, 4, 4), columnRoi(2, 2, 1, 4);
+    Mat buf8u(20, 20, CV_8UC1, Scalar(250)), buf;
+    for (int r = 0; r < 4; r++)
+    {
+        for (int c = 0; c < 4; c++)
+            buf8u(rampRoi).at<uchar>(r, c) = (uchar)(r * 40 + c * 8);
+        buf8u(columnRoi).at<uchar>(r, 0) = (uchar)(10 + r * 10);
+    }
+    buf8u.convertTo(buf, depth);
+
+    const struct { Rect roi; Size size; Point2f center; std::vector<float> expected; } cases[] = {
+        // the window crosses the top and the right edges
+        { rampRoi, Size(3, 3), Point2f(3.f, 0.f), { 16, 24, 24, 16, 24, 24, 56, 64, 64 } },
+        { columnRoi, Size(3, 3), Point2f(0.f, 0.f), { 10, 10, 10, 10, 10, 10, 20, 20, 20 } },
+        // the window is to the left of the image
+        { rampRoi, Size(1, 1), Point2f(-2.75f, 3.f), { 120 } },
+    };
+    for (const auto& tc : cases)
+    {
+        SCOPED_TRACE(cv::format("image=%dx%d center=(%g, %g)", tc.roi.width, tc.roi.height, tc.center.x, tc.center.y));
+        Mat patch, patch32f;
+        getRectSubPix(buf(tc.roi), tc.size, tc.center, patch, ddepth);
+        patch.convertTo(patch32f, CV_32F);
+        Mat expected = Mat(tc.expected).reshape(1, tc.size.height);
+        EXPECT_LE(cvtest::norm(patch32f, expected, NORM_INF), 1e-3) << patch32f;
+    }
+}
+
+INSTANTIATE_TEST_CASE_P(/**/, Imgproc_GetRectSubPix_Border, testing::Values(
+    testing::make_tuple(CV_8U, CV_8U), testing::make_tuple(CV_8U, CV_32F), testing::make_tuple(CV_32F, CV_32F)));
+
+
 }} // namespace
 /* End of file. */