From 92f754c6755ff898fdbd39bc7dab3edca0b96285 Mon Sep 17 00:00:00 2001
From: Dmitry Kurtaev <dmitry.kurtaev+github@gmail.com>
Date: Thu, 25 Oct 2018 10:48:23 +0300
Subject: [PATCH] Add methods to reshape Mat in Java by array of shapes and
 retreive sizes of each dimension.

---
 modules/core/misc/java/src/java/core+Mat.java | 30 ++++++++++++
 modules/core/misc/java/test/MatTest.java      | 13 +++++
 modules/java/generator/src/cpp/Mat.cpp        | 47 +++++++++++++++++++
 3 files changed, 90 insertions(+)

diff --git a/modules/core/misc/java/src/java/core+Mat.java b/modules/core/misc/java/src/java/core+Mat.java
index c975f0c44b..c75f9d5c01 100644
--- a/modules/core/misc/java/src/java/core+Mat.java
+++ b/modules/core/misc/java/src/java/core+Mat.java
@@ -681,6 +681,18 @@ public class Mat {
         return retVal;
     }
 
+    //
+    // C++: Mat Mat::reshape(int cn, int newndims, const int* newsz)
+    //
+
+    // javadoc: Mat::reshape(cn, newshape)
+    public Mat reshape(int cn, int[] newshape)
+    {
+        Mat retVal = new Mat(n_reshape_1(nativeObj, cn, newshape.length, newshape));
+
+        return retVal;
+    }
+
     //
     // C++: Mat Mat::row(int y)
     //
@@ -794,6 +806,18 @@ public class Mat {
         return retVal;
     }
 
+    //
+    // C++: int Mat::size(int i)
+    //
+
+    // javadoc: Mat::size(int i)
+    public int size(int i)
+    {
+        int retVal = n_size_i(nativeObj, i);
+
+        return retVal;
+    }
+
     //
     // C++: size_t Mat::step1(int i = 0)
     //
@@ -1271,6 +1295,9 @@ public class Mat {
 
     private static native long n_reshape(long nativeObj, int cn);
 
+    // C++: Mat Mat::reshape(int cn, int newndims, const int* newsz)
+    private static native long n_reshape_1(long nativeObj, int cn, int newndims, int[] newsz);
+
     // C++: Mat Mat::row(int y)
     private static native long n_row(long nativeObj, int y);
 
@@ -1294,6 +1321,9 @@ public class Mat {
     // C++: Size Mat::size()
     private static native double[] n_size(long nativeObj);
 
+    // C++: int Mat::size(int i)
+    private static native int n_size_i(long nativeObj, int i);
+
     // C++: size_t Mat::step1(int i = 0)
     private static native long n_step1(long nativeObj, int i);
 
diff --git a/modules/core/misc/java/test/MatTest.java b/modules/core/misc/java/test/MatTest.java
index a497bba1f2..f0f4fdc200 100644
--- a/modules/core/misc/java/test/MatTest.java
+++ b/modules/core/misc/java/test/MatTest.java
@@ -817,6 +817,19 @@ public class MatTest extends OpenCVTestCase {
         assertMatEqual(truth, dst);
     }
 
+    public void testReshapeIntIntArray() {
+        Mat src = new Mat(6, 5, CvType.CV_8UC3, new Scalar(0));
+        assertEquals(2, src.dims());
+        assertEquals(src.rows(), src.size(0));
+        assertEquals(src.cols(), src.size(1));
+
+        int[] newShape = {1, src.channels() * src.cols(), 1, src.rows()};
+        dst = src.reshape(1, newShape);
+        assertEquals(newShape.length, dst.dims());
+        for (int i = 0; i < newShape.length; ++i)
+            assertEquals(newShape[i], dst.size(i));
+    }
+
     public void testRow() {
         Mat row = gray0.row(0);
         assertEquals(1, row.rows());
diff --git a/modules/java/generator/src/cpp/Mat.cpp b/modules/java/generator/src/cpp/Mat.cpp
index db9f1936da..e222cb5904 100644
--- a/modules/java/generator/src/cpp/Mat.cpp
+++ b/modules/java/generator/src/cpp/Mat.cpp
@@ -528,7 +528,30 @@ JNIEXPORT jint JNICALL Java_org_opencv_core_Mat_n_1cols
     return 0;
 }
 
+//
+//  int Mat::size(int i)
+//
 
+JNIEXPORT jint JNICALL Java_org_opencv_core_Mat_n_1size_1i__JI
+  (JNIEnv* env, jclass, jlong self, jint i);
+
+JNIEXPORT jint JNICALL Java_org_opencv_core_Mat_n_1size_1i__JI
+  (JNIEnv* env, jclass, jlong self, jint i)
+{
+    static const char method_name[] = "Mat::n_1size_1i__JI()";
+    try {
+        LOGD("%s", method_name);
+        Mat* me = (Mat*) self; //TODO: check for NULL
+        int _retval_ = me->size[i];
+        return _retval_;
+    } catch(const std::exception &e) {
+        throwJavaException(env, &e, method_name);
+    } catch (...) {
+        throwJavaException(env, 0, method_name);
+    }
+
+    return 0;
+}
 
 //
 //  void Mat::convertTo(Mat& m, int rtype, double alpha = 1, double beta = 0)
@@ -1307,7 +1330,31 @@ JNIEXPORT jlong JNICALL Java_org_opencv_core_Mat_n_1reshape__JI
     return 0;
 }
 
+//
+//  Mat Mat::reshape(int cn, int[] newshape)
+//
+
+JNIEXPORT jlong JNICALL Java_org_opencv_core_Mat_n_1reshape_11
+  (JNIEnv* env, jclass, jlong self, jint cn, jint newndims, jintArray newshape);
+
+JNIEXPORT jlong JNICALL Java_org_opencv_core_Mat_n_1reshape_11
+  (JNIEnv* env, jclass, jlong self, jint cn, jint newndims, jintArray newshape)
+{
+    static const char method_name[] = "Mat::n_1reshape_11";
+    try {
+        LOGD("%s", method_name);
+        Mat* me = (Mat*) self; //TODO: check for NULL
+        int* newsz = (int*)env->GetPrimitiveArrayCritical(newshape, 0);
+        Mat _retval_ = me->reshape( cn, newndims, newsz );
+        return (jlong) new Mat(_retval_);
+    } catch(const std::exception &e) {
+        throwJavaException(env, &e, method_name);
+    } catch (...) {
+        throwJavaException(env, 0, method_name);
+    }
 
+    return 0;
+}
 
 //
 //  Mat Mat::row(int y)