Fixed color conversion bug

samples/android/tutorial-3-native/jni/jni_part.cpp

@@ -8,25 +8,27 @@ using namespace std;
 using namespace cv;
 
 extern "C" {
-JNIEXPORT void JNICALL Java_org_opencv_samples_tutorial3_Sample3View_FindFeatures(JNIEnv* env, jobject thiz, jint width, jint height, jbyteArray yuv, jintArray rgba)
+JNIEXPORT void JNICALL Java_org_opencv_samples_tutorial3_Sample3View_FindFeatures(JNIEnv* env, jobject thiz, jint width, jint height, jbyteArray yuv, jintArray bgra)
 {
     jbyte* _yuv  = env->GetByteArrayElements(yuv, 0);
-    jint*  _rgba = env->GetIntArrayElements(rgba, 0);
+    jint*  _bgra = env->GetIntArrayElements(bgra, 0);
 
     Mat myuv(height + height/2, width, CV_8UC1, (unsigned char *)_yuv);
-    Mat mrgba(height, width, CV_8UC4, (unsigned char *)_rgba);
+    Mat mbgra(height, width, CV_8UC4, (unsigned char *)_bgra);
     Mat mgray(height, width, CV_8UC1, (unsigned char *)_yuv);
 
-    cvtColor(myuv, mrgba, CV_YUV420i2BGR, 4);
+    //Please make attention about BGRA byte order
+    //ARGB stored in java as int array becomes BGRA at native level
+    cvtColor(myuv, mbgra, CV_YUV420sp2BGR, 4);
 
     vector<KeyPoint> v;
 
     FastFeatureDetector detector(50);
     detector.detect(mgray, v);
     for( size_t i = 0; i < v.size(); i++ )
-        circle(mrgba, Point(v[i].pt.x, v[i].pt.y), 10, Scalar(0,0,255,255));
+        circle(mbgra, Point(v[i].pt.x, v[i].pt.y), 10, Scalar(0,0,255,255));
 
-    env->ReleaseIntArrayElements(rgba, _rgba, 0);
+    env->ReleaseIntArrayElements(bgra, _bgra, 0);
     env->ReleaseByteArrayElements(yuv, _yuv, 0);
 }