HI when I try to call a native method Features2D + Homography to find a known object I had errors telque double dist = matches[i].distance; matches[i].distance < 3*min_dist good_matches.push_back( matches[i]); line
console : Compile++ thumb : native_sample <= jni_part.cpp Prebuilt : libgnustl_static.a <= <ndk>/sources/cxx-stl/gnu-libstdc++/4.6/libs/armeabi-v7a/ SharedLibrary : libnative_sample.so Install : libnative_sample.so => libs/armeabi-v7a/libnative_sample.so mirlo06@mirlo06-Satellite-L500:~/OpenCV4android/samples/tutorial-3-native$ /opt/android-ndk/ndk-build Compile++ thumb : native_sample <= jni_part.cpp Prebuilt : libgnustl_static.a <= <ndk>/sources/cxx-stl/gnu-libstdc++/4.6/libs/armeabi-v7a/ SharedLibrary : libnative_sample.so /opt/android-ndk/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld: warning: hidden symbol '__aeabi_atexit' in ./obj/local/armeabi-v7a/libgnustl_static.a(atexit_arm.o) is referenced by DSO ../../sdk/native/jni/../libs/armeabi-v7a/libopencv_java.so /opt/android-ndk/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld: ./obj/local/armeabi-v7a/objs/native_sample/jni_part.o: in function cv::SURF::~SURF():../../sdk/native/jni/include/opencv2/nonfree/features2d.hpp:107: error: undefined reference to 'vtable for cv::SURF' /opt/android-ndk/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld: ./obj/local/armeabi-v7a/objs/native_sample/jni_part.o: in function cv::SURF::~SURF():../../sdk/native/jni/include/opencv2/nonfree/features2d.hpp:107: error: undefined reference to 'VTT for cv::SURF' /opt/android-ndk/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld: ./obj/local/armeabi-v7a/objs/native_sample/jni_part.o: in function Java_org_opencv_samples_tutorial3_Sample3Native_FindFeatures:jni/jni_part.cpp:26: error: undefined reference to 'cv::SURF::SURF(double, int, int, bool, bool)' /opt/android-ndk/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld: ./obj/local/armeabi-v7a/objs/native_sample/jni_part.o: in function Java_org_opencv_samples_tutorial3_Sample3Native_FindFeatures:jni/jni_part.cpp:34: error: undefined reference to 'cv::SURF::SURF()' collect2: ld returned 1 exit status make: * [obj/local/armeabi-v7a/libnative_sample.so] Error 1 here is the code
include <jni.h>
#include <opencv2 core="" core.hpp="">
include <opencv2 nonfree="" features2d.hpp="">
include <opencv2 imgproc="" imgproc.hpp="">
include <opencv2 highgui="" highgui.hpp="">
include <opencv2 calib3d="" calib3d.hpp="">
include <vector>
using namespace cv; using namespace std;
extern "C" { JNIEXPORT void JNICALL Java_org_opencv_samples_tutorial3_Sample3Native_FindFeatures(JNIEnv*, jobject, jlong addrGray, jlong addrRgba);
JNIEXPORT void JNICALL Java_org_opencv_samples_tutorial3_Sample3Native_FindFeatures(JNIEnv*, jobject, jlong addrGray, jlong addrRgba) {
Mat& img_object = *(Mat*)addrGray;
Mat& img_scene = *(Mat*)addrRgba;
int minHessian = 400;
SurfFeatureDetector detector( minHessian );
vector<KeyPoint> keypoints_object, keypoints_scene;
detector.detect( img_object, keypoints_object );
detector.detect( img_scene, keypoints_scene );
//-- Step 2: Calculate descriptors (feature vectors)
SurfDescriptorExtractor extractor;
Mat descriptors_object, descriptors_scene;
extractor.compute( img_object, keypoints_object, descriptors_object );
extractor.compute( img_scene, keypoints_scene, descriptors_scene );
//-- Step 3: Matching descriptor vectors using FLANN matcher
FlannBasedMatcher matcher;
vector< DMatch > matches;
matcher.match( descriptors_object, descriptors_scene, matches );
double max_dist = 0; double min_dist = 100;
//-- Quick calculation of max and min distances between keypoints
for( int i = 0; i < descriptors_object.rows; i++ )
{ double dist = matches[i].distance;
if( dist < min_dist ) min_dist = dist;
if( dist > max_dist ) max_dist = dist;
}
//-- Draw only "good" matches (i.e. whose distance is less than 3*min_dist )
vector< DMatch > good_matches;
for( int i = 0; i < descriptors_object.rows; i++ )
{ if( matches[i].distance < 3*min_dist )
{ good_matches.push_back( matches[i]); }
}
Mat img_matches;
drawMatches( img_object, keypoints_object, img_scene, keypoints_scene,
good_matches, img_matches, Scalar::all(-1), Scalar::all(-1),
vector<char>(), DrawMatchesFlags::NOT_DRAW_SINGLE_POINTS );
//-- Localize the object
vector<Point2f> obj;
vector<Point2f> scene;
for( int i = 0; i < good_matches.size(); i++ )
{
//-- Get the keypoints from the good matches
obj.push_back( keypoints_object[ good_matches[i].queryIdx ].pt );
scene.push_back( keypoints_scene[ good_matches[i].trainIdx ].pt );
}
Mat H = findHomography( obj, scene, CV_RANSAC );
//-- Get the corners from the image_1 ( the object to be "detected" )
vector<Point2f> obj_corners(4);
obj_corners[0] = cvPoint(0,0); obj_corners[1] = cvPoint( img_object.cols, 0 );
obj_corners[2] = cvPoint( img_object.cols, img_object.rows ); obj_corners[3] = cvPoint( 0, img_object.rows );
vector<Point2f> scene_corners(4);
perspectiveTransform( obj_corners, scene_corners, H);
//-- Draw lines between the corners (the mapped object in the scene - image_2 )
line( img_matches, scene_corners[0] + Point2f( img_object.cols, 0), scene_corners[1] + Point2f( img_object.cols, 0), Scalar(0, 255, 0), 4 );
line( img_matches, scene_corners[1] + Point2f( img_object.cols, 0), scene_corners[2] + Point2f( img_object.cols, 0), Scalar( 0, 255, 0), 4 );
line( img_matches, scene_corners[2] + Point2f( img_object.cols, 0), scene_corners[3] + Point2f( img_object.cols, 0), Scalar( 0, 255, 0), 4 );
line( img_matches, scene_corners[3] + Point2f( img_object.cols, 0), scene_corners[0] + Point2f( img_object.cols, 0), Scalar( 0, 255, 0), 4 );
img_scene=img_matches;
} }
