Real-time object recognition on Android with a FAST detector

Question

The purpose of this work is to extract key points in real time from an existing image during the video scene. In the frame, execution is performed that does not work, because of the correspondence, is that I can simply display the key points of correspondence in the form of circles on the image in real time

class Sample1View extends SampleViewBase { public static final int VIEW_MODE_RGBA = 0; public static final int VIEW_MODE_BLUE = 1; public static final int VIEW_MODE_YELLOW = 2; public static final int VIEW_MODE_DE = 3; private Mat mYuv; private Mat mRgba; private Mat mGraySubmat; private Mat mResult; private Mat mIntermediateMat; private Bitmap mBitmap; private int mViewMode; private Mat mColor; private Mat mHsv; TimingLogger timings; private Mat img1; private Mat descriptors; private MatOfKeyPoint keypoints; private FeatureDetector detector; private DescriptorExtractor descriptor; private DescriptorMatcher matcher; private static final String TAG ="Sample::View"; public Sample1View(Context context) { super(context); mViewMode = VIEW_MODE_RGBA; try { img1=Utils.loadResource(getContext(), R.drawable.wings); } catch (IOException e) { // TODO Auto-generated catch block Log.w("Activity::LoadResource","Unable to load resource R.drawable.wings"); e.printStackTrace(); } descriptors = new Mat(); keypoints = new MatOfKeyPoint(); detector = FeatureDetector.create(FeatureDetector.FAST); detector.detect(img1, keypoints); descriptor = DescriptorExtractor.create(DescriptorExtractor.ORB); descriptor.compute(img1, keypoints, descriptors); matcher = DescriptorMatcher.create(DescriptorMatcher.BRUTEFORCE_HAMMING); } @Override protected void onPreviewStarted(int previewWidth, int previewHeight) { Log.i(TAG, "preview Started"); synchronized (this) { mYuv = new Mat(getFrameHeight() + getFrameHeight() / 2, getFrameWidth(), CvType.CV_8UC1); mGraySubmat = mYuv.submat(0, getFrameHeight(), 0, getFrameWidth()); mRgba = new Mat(); mIntermediateMat = new Mat(); mBitmap = Bitmap.createBitmap(previewWidth, previewHeight, Bitmap.Config.ARGB_8888); mHsv = new Mat(); mColor = new Mat(); mResult = new Mat(); } } @Override protected void onPreviewStopped() { Log.i(TAG, "preview Stopped"); if(mBitmap != null) { mBitmap.recycle(); } synchronized (this) { // Explicitly deallocate Mats if (mYuv != null) mYuv.release(); if (mRgba != null) mRgba.release(); if (mGraySubmat != null) mGraySubmat.release(); if (mIntermediateMat != null) mIntermediateMat.release(); mYuv = null; mRgba = null; mGraySubmat = null; mIntermediateMat = null; if (mResult != null) mResult.release(); if (mHsv != null) mHsv.release(); if (mColor != null) mColor.release(); mColor = null; mResult = null; mHsv = null; } } 

// cvt_YUVtoRGBtoHSV:

  @Override protected Bitmap processFrame(byte[] data) { mYuv.put(0, 0, data); final int viewMode = mViewMode; ColorDetection.cvt_YUVtoRGBtoHSV(mYuv,mGraySubmat); MatOfKeyPoint mKeyPoints = new MatOfKeyPoint(); MatOfDMatch matches = new MatOfDMatch(); detector.detect(mGraySubmat, mKeyPoints); descriptor.compute(mGraySubmat, mKeyPoints, mIntermediateMat); matcher.match(mIntermediateMat, descriptors, matches); mIntermediateMat2.create(resultSize, CvType.CV_8UC1); Features2d.drawMatches(mGraySubmat, mKeyPoints, mGraySubmat, mKeyPoints, matches, mIntermediateMat2); Imgproc.resize(mIntermediateMat2, mIntermediateMat2, mRgba.size()); Imgproc.cvtColor(mIntermediateMat2, mRgba, Imgproc.COLOR_RGBA2BGRA, 4); break; } Bitmap bmp = mBitmap; try { Utils.matToBitmap(mRgba, bmp); } catch(Exception e) { Log.e("org.opencv.samples.*", "Utils.matToBitmap() throws an exception: " + e.getMessage()); bmp.recycle(); bmp = null; } return bmp; } public void setViewMode(int viewMode) { mViewMode = viewMode; } } 

and what's in log

CvException [org.opencv.core.CvException: /home/reports/ci/slave/50-SDK/opencv/modules/features2d/src/draw.cpp: 207: error: (-215) i1> = 0 && i1 < static_cast (keypoints1.size ()) in the function void cv :: drawMatches (const cv :: Mat &, const std :: vector &, const cv :: Mat &, const std :: vector &, const std :: vector & , cv :: Mat &, const Scalar &, const Scalar &, const std :: vector &, int)

Answer 1

This post is a little old, but I give it an answer.

The drawMatches function for the first four parameters is invalid. The first two and two of the second are the same.
You can change the first four parameters of drawMatches from (mGraySubmat, mKeyPoints, mGraySubmat, mKeyPoints, ...);
to
(mGraySubmat, mKeyPoints, img1, key points, ...);
or
(img1, key points, mGraySubmat, mKeyPoints, ...);
Use the one that works for you.

For other readers, if they have the same problem, they may try to change the first two parameters with the second two parameters.
E.g.
(image1, keypointsImage1, image2, keypointsImage2, ...);
in
(image2, keypointsImage2, image1, keypointsImage1, ...);

For me, she corrected my mistake.