Correct MinMaxIdx function minIdx and maxIdx

core.cpp

@@ -654,7 +654,14 @@ void Mat_Min(Mat src1, Mat src2, Mat dst) {
 }
 
 void Mat_MinMaxIdx(Mat m, double* minVal, double* maxVal, int* minIdx, int* maxIdx) {
-    cv::minMaxIdx(*m, minVal, maxVal, minIdx, maxIdx);
+    int cMinIdx[m->dims];
+    int cMaxIdx[m->dims];
+    cv::minMaxIdx(*m, minVal, maxVal, cMinIdx, cMaxIdx);
+
+    for(unsigned int a = 0; a < sizeof(cMinIdx)/sizeof(cMinIdx[0]); a++) {
+        minIdx[a] = cMinIdx[a];
+        maxIdx[a] = cMaxIdx[a];
+    }
 }
 
 void Mat_MinMaxLoc(Mat m, double* minVal, double* maxVal, Point* minLoc, Point* maxLoc) {

core.go

@@ -1512,15 +1512,37 @@ func Min(src1, src2 Mat, dst *Mat) {
 //
 // For further details, please see:
 // https://docs.opencv.org/master/d2/de8/group__core__array.html#ga7622c466c628a75d9ed008b42250a73f
-func MinMaxIdx(input Mat) (minVal, maxVal float32, minIdx, maxIdx int) {
+func MinMaxIdx(input Mat) (minVal, maxVal float32, minIdx, maxIdx []int) {
 	var cMinVal C.double
 	var cMaxVal C.double
-	var cMinIdx C.int
-	var cMaxIdx C.int
 
-	C.Mat_MinMaxIdx(input.p, &cMinVal, &cMaxVal, &cMinIdx, &cMaxIdx)
+	dims := len(input.Size())
+	cMinIdx := (*C.int)(C.malloc(C.size_t(C.sizeof_int * dims)))
+	cMaxIdx := (*C.int)(C.malloc(C.size_t(C.sizeof_int * dims)))
+	defer C.free(unsafe.Pointer(cMinIdx))
+	defer C.free(unsafe.Pointer(cMaxIdx))
 
-	return float32(cMinVal), float32(cMaxVal), int(minIdx), int(maxIdx)
+	C.Mat_MinMaxIdx(input.p, &cMinVal, &cMaxVal, cMinIdx, cMaxIdx)
+
+	h := &reflect.SliceHeader{
+		Data: uintptr(unsafe.Pointer(cMinIdx)),
+		Len:  dims,
+		Cap:  dims,
+	}
+	minIndex := *(*[]C.int)(unsafe.Pointer(h))
+
+	h = &reflect.SliceHeader{
+		Data: uintptr(unsafe.Pointer(cMaxIdx)),
+		Len:  dims,
+		Cap:  dims,
+	}
+	maxIndex := *(*[]C.int)(unsafe.Pointer(h))
+
+	for i := 0; i < dims; i++ {
+		minIdx = append(minIdx, int(minIndex[i]))
+		maxIdx = append(maxIdx, int(maxIndex[i]))
+	}
+	return float32(cMinVal), float32(cMaxVal), minIdx, maxIdx
 }
 
 // MinMaxLoc finds the global minimum and maximum in an array.

core_test.go

@@ -2574,14 +2574,59 @@ func TestMatMinMaxIdx(t *testing.T) {
 	src.SetFloatAt(3, 3, 17)
 	src.SetFloatAt(4, 4, 16)
 
-	minVal, maxVal, _, _ := MinMaxIdx(src)
-
+	minVal, maxVal, minIdx, maxIdx := MinMaxIdx(src)
 	if minVal != 0 {
 		t.Error("TestMatMinMaxIdx minVal should be 0.")
 	}
 	if maxVal != 17 {
 		t.Errorf("TestMatMinMaxIdx maxVal should be 17, was %f", maxVal)
 	}
+	if minIdx[0] != 0 || minIdx[1] != 0 {
+		t.Errorf("TestMatMinMaxIdx minIdx should be [0,0], was [%d,%d]", minIdx[0], minIdx[1])
+	}
+	if maxIdx[0] != 3 || maxIdx[1] != 3 {
+		t.Errorf("TestMatMinMaxIdx maxIdx should be [3,3], was [%d,%d]", maxIdx[0], maxIdx[1])
+	}
+}
+
+func TestMatMinMaxIdx3d(t *testing.T) {
+	src := NewMatWithSizes([]int{3,3,3}, MatTypeCV32F)
+	defer src.Close()
+
+	for x := 0; x < 3; x++ {
+		for y := 0; y < 3; y++ {
+			for z := 0; z < 3; z++ {
+				src.SetFloatAt3(x, y, z, 0)
+			}
+		}
+	}
+
+	src.SetFloatAt3(2, 1, 2, 2)
+
+	minVal, maxVal, minIdx, maxIdx := MinMaxIdx(src)
+	if len(minIdx) != 3 {
+		t.Errorf("minIdx should have 3 dimensions. %d found", len(minIdx))
+	}
+
+	if len(maxIdx) != 3 {
+		t.Errorf("maxIdx should have 3 dimensions. %d found", len(maxIdx))
+	}
+
+	if minVal != 0 {
+		t.Errorf("TestMatMinMaxIdx3d minVal expected 0, got %f", minVal)
+	}
+	if maxVal != 2 {
+		t.Errorf("TestMatMinMaxIdx3d maxVal should be 2, was %f", maxVal)
+	}
+
+
+	if maxIdx[0] != 2 || maxIdx[1] != 1 || maxIdx[2] != 2 {
+		t.Errorf("TestMatMinMaxIdx3d maxIdx should be [2,1,2], was [%d,%d,%d]", maxIdx[0], maxIdx[1], maxIdx[2])
+	}
+
+	if minIdx[0] != 0 || minIdx[1] != 0 || minIdx[2] != 0 {
+		t.Errorf("TestMatMinMaxIdx3d minIdx should be [0,0,0], was [%d,%d,%d]", minIdx[0], minIdx[1], minIdx[2])
+	}
 }
 
 func TestMixChannels(t *testing.T) {