core: remove constructors from C API structures

POD structures can't have constructors.

modules/core/src/matrix_c.cpp

@@ -4,20 +4,24 @@
 
 // glue
 
-CvMatND::CvMatND(const cv::Mat& m)
+CvMatND cvMatND(const cv::Mat& m)
 {
-    cvInitMatNDHeader(this, m.dims, m.size, m.type(), m.data );
+    CvMatND self;
+    cvInitMatNDHeader(&self, m.dims, m.size, m.type(), m.data );
     int i, d = m.dims;
     for( i = 0; i < d; i++ )
-        dim[i].step = (int)m.step[i];
-    type |= m.flags & cv::Mat::CONTINUOUS_FLAG;
+        self.dim[i].step = (int)m.step[i];
+    self.type |= m.flags & cv::Mat::CONTINUOUS_FLAG;
+    return self;
 }
 
-_IplImage::_IplImage(const cv::Mat& m)
+_IplImage cvIplImage(const cv::Mat& m)
 {
+    _IplImage self;
     CV_Assert( m.dims <= 2 );
-    cvInitImageHeader(this, m.size(), cvIplDepth(m.flags), m.channels());
-    cvSetData(this, m.data, (int)m.step[0]);
+    cvInitImageHeader(&self, cvSize(m.size()), cvIplDepth(m.flags), m.channels());
+    cvSetData(&self, m.data, (int)m.step[0]);
+    return self;
 }
 
 namespace cv {

modules/imgproc/include/opencv2/imgproc/types_c.h

@@ -410,7 +410,7 @@ typedef struct CvMoments
     double  mu20, mu11, mu02, mu30, mu21, mu12, mu03; /**< central moments */
     double  inv_sqrt_m00; /**< m00 != 0 ? 1/sqrt(m00) : 0 */
 
-#ifdef __cplusplus
+#if defined(CV__ENABLE_C_API_CTORS) && defined(__cplusplus)
     CvMoments(){}
     CvMoments(const cv::Moments& m)
     {
@@ -430,6 +430,36 @@ typedef struct CvMoments
 }
 CvMoments;
 
+#ifdef __cplusplus
+} // extern "C"
+
+CV_INLINE CvMoments cvMoments()
+{
+#if !defined(CV__ENABLE_C_API_CTORS)
+    CvMoments self = CV_STRUCT_INITIALIZER; return self;
+#else
+    return CvMoments();
+#endif
+}
+
+CV_INLINE CvMoments cvMoments(const cv::Moments& m)
+{
+#if !defined(CV__ENABLE_C_API_CTORS)
+    double am00 = std::abs(m.m00);
+    CvMoments self = {
+        m.m00, m.m10, m.m01, m.m20, m.m11, m.m02, m.m30, m.m21, m.m12, m.m03,
+        m.mu20, m.mu11, m.mu02, m.mu30, m.mu21, m.mu12, m.mu03,
+        am00 > DBL_EPSILON ? 1./std::sqrt(am00) : 0
+    };
+    return self;
+#else
+    return CvMoments(m);
+#endif
+}
+
+extern "C" {
+#endif // __cplusplus
+
 /** Hu invariants */
 typedef struct CvHuMoments
 {