Develop Reference

Mat to Bitmap exception thrown

The following are My Code for drawing border in openCV
Mat src = new Mat(imageChosen.getWidth(), imageChosen.getHeight(), CvType.CV_8UC3);
Utils.bitmapToMat(imageChosen, src);
Mat dst = new Mat(imageChosen.getWidth(), imageChosen.getHeight(), CvType.CV_8UC3);
Core.copyMakeBorder(src, dst, 10, 10, 10, 10, Core.BORDER_CONSTANT, new Scalar(0,0,0));
Bitmap b = Bitmap.createBitmap(imageChosen.getWidth()+20, imageChosen.getHeight()+20,Bitmap.Config.ARGB_8888);
Utils.matToBitmap(src, b);
and i don't know why it throw
E/cv::error(): OpenCV Error: Assertion failed (src.dims == 2 && info.height == (uint32_t)src.rows && info.width == (uint32_t)src.cols) in void Java_org_opencv_android_Utils_nMatToBitmap2(JNIEnv*, jclass, jlong, jobject, jboolean), file /Volumes/Linux/builds/master_pack-android/opencv/modules/java/generator/src/cpp/utils.cpp, line 97
E/org.opencv.android.Utils: nMatToBitmap catched cv::Exception: /Volumes/Linux/builds/master_pack-android/opencv/modules/java/generator/src/cpp/utils.cpp:97: error: (-215) src.dims == 2 && info.height == (uint32_t)src.rows && info.width == (uint32_t)src.cols in function void Java_org_opencv_android_Utils_nMatToBitmap2(JNIEnv*, jclass, jlong, jobject, jboolean)
Any help/ideas would be greatly appreciated, thanks.

If you take a look at the documentation of Mat, you can see that the constructor expects its params in the following order: rows, columns.
You're passing the width (columns) first and the height (rows) after.
Instead of the following:
Mat src = new Mat(imageChosen.getWidth(), imageChosen.getHeight(), CvType.CV_8UC3);
You should pass the height first:
Mat src = new Mat(imageChosen.getHeight(), imageChosen.getWidth(), CvType.CV_8UC3);
For both src and dst.

OpenCV resize failing

I have an application using A JavaCameraView from OpenCV for android that uses the following callback
CameraBridgeViewBase.CvCameraViewListener cvListener = new CameraBridgeViewBase.CvCameraViewListener() {
#Override
public void onCameraViewStarted(int width, int height) {
}
#Override
public void onCameraViewStopped() {
}
#Override
public Mat onCameraFrame(Mat inputFrame) {
Size newSize = new Size(400, 200);
Mat fit = new Mat(newSize, CvType.CV_8UC4);
Imgproc.resize(inputFrame,fit,newSize);
return fit;
}
};
However, when the resizing happens, an error occurs saying
E/CameraBridge: Utils.matToBitmap() throws an exception: /Volumes/Linux/builds/master_pack-android/opencv/modules/java/generator/src/cpp/utils.cpp:97: error: (-215) src.dims == 2 && info.height == (uint32_t)src.rows && info.width == (uint32_t)src.cols in function void Java_org_opencv_android_Utils_nMatToBitmap2(JNIEnv*, jclass, jlong, jobject, jboolean)
E/cv::error(): OpenCV Error: Assertion failed (src.dims == 2 && info.height == (uint32_t)src.rows && info.width == (uint32_t)src.cols) in void Java_org_opencv_android_Utils_nMatToBitmap2(JNIEnv*, jclass, jlong, jobject, jboolean), file /Volumes/Linux/builds/master_pack-android/opencv/modules/java/generator/src/cpp/utils.cpp, line 97
E/org.opencv.android.Utils: nMatToBitmap catched cv::Exception: /Volumes/Linux/builds/master_pack-android/opencv/modules/java/generator/src/cpp/utils.cpp:97: error: (-215) src.dims == 2 && info.height == (uint32_t)src.rows && info.width == (uint32_t)src.cols in function void Java_org_opencv_android_Utils_nMatToBitmap2(JNIEnv*, jclass, jlong, jobject, jboolean)
E/CameraBridge: Mat type: Mat [ 244*432*CV_8UC4, isCont=true, isSubmat=false, nativeObj=0x1ade1b0, dataAddr=0x5dbc6010 ]
E/CameraBridge: Bitmap type: 240*160
Nothing happens in the actual UI. I'm not sure why I'm seeing this error, since I'm never calling Utils.bitmapToMat or Utils.matToBitmap. When I take out the Imgproc.resize(inputFrame,fit,newSize); and return the inputFrame, everything works as expected.

For onCameraFrame, I believe you have to return the Mat of the same size as your inputFrame. Since the resolution of the image obtained from your camera is
240*160 (refer this-> E/CameraBridge: Bitmap type: 240*160) you will need to resize your Mat fit back to 240*160 after you done your processing..
A simple fix:
#Override
public Mat onCameraFrame(Mat inputFrame) {
Size newSize = new Size(400, 200);
Mat fit = new Mat(newSize, CvType.CV_8UC4);
Imgproc.resize(inputFrame,fit,newSize);
/**Your processing code */
Imgproc.resize(fit,fit,inputFrame.size()); <- Add this line
return fit;
}
To change the size of the image you receive from camera, you have to call mOpenCvCameraView.setMaxFrameSize(width, height); but the resolution will be chosen from the list of resolutions supported by the camera hardware. To know more why you can't set an arbitrary value for the resolution you'll need to read on Android Camera API, since that's what OpenCV uses to grab the images at the back :)

OpenCV4Android - find/drawContour error

What I'm attempting to do is take a thresholded image and perform findContours on it then draw it out to a rotation corrected image. The rotation corrected image and the thresholded image work as expected so I'm at a bit of a loss figuring out why this would crash. The thersholded image is a grey version of the rotation corrected image that has had a binary threshold applied to it.
public void findImageContours(Mat passedThreshInt, Mat passedRotatedInit)
{
/* Get Thresholded input image */
Mat initThresh = passedThreshInt.clone();
/* Get image to draw Contours on */
Mat initRotated = passedRotatedInit.clone();
/* Get contours from threshold image */
List<MatOfPoint> contours = new ArrayList<MatOfPoint>();
Imgproc.findContours(initThresh, contours, mHierarchy, Imgproc.RETR_EXTERNAL, Imgproc.CHAIN_APPROX_SIMPLE);
/* Draw Contours */
Scalar CONTOUR_COLOR = new Scalar(255,0,0,255);
Log.e(TAG, "Contours count: " + contours.size());
Imgproc.drawContours(initRotated, contours, -1, CONTOUR_COLOR);
/* Save Output */
contouredInit = initRotated.clone(); //ContouredInit is Global
Utils.matToBitmap(contouredInit, contouredBitmapInit); // contouredBitmapInit is Global
}
Error:
OpenCV Error: Assertion failed (src.dims == 2 && info.height == (uint32_t)src.rows && info.width == (uint32_t)src.cols) in void Java_org_opencv_android_Utils_nMatToBitmap2(JNIEnv*, jclass, jlong, jobject, jboolean), file /hdd2/buildbot/slaves/slave_ardbeg1/50-SDK/opencv/modules/java/generator/src/cpp/utils.cpp, line 97
nMatToBitmap catched cv::Exception: /hdd2/buildbot/slaves/slave_ardbeg1/50-SDK/opencv/modules/java/generator/src/cpp/utils.cpp:97: error: (-215) src.dims == 2 && info.height == (uint32_t)src.rows && info.width == (uint32_t)src.cols in function void Java_org_opencv_android_Utils_nMatToBitmap2(JNIEnv*, jclass, jlong, jobject, jboolean)
And after that a JDI Dispatch Error.

Dimensions of Bitmap has to match the dimensions of OpenCV Mat. I suggest you create Bitmap as below.
Bitmap bitmapImg = Bitmap.createBitmap( matImg.cols(), matImg.rows(), Bitmap.Config.ARGB_8888 );
For future errors of these kind, a look into opencv github repository(1) might help you.

assertion failure for backprojection

I try to make object tracking using CamShift.
But I have received error.This error became from back projection
Here is error message from LOGCAT
Assertion failed (rsz == dims*2 || (rsz == 2 && _1d) || (rsz == 0 && images.depth(0) == CV_8U)) in void cv::calcBackProject(cv::InputArrayOfArrays, const std::vector&, cv::InputArray, cv::OutputArray, const std::vector&, double)
Here is my code. Can anybody help me?(sory my poor eng)
public Mat onCameraFrame(CvCameraViewFrame inputFrame)
{
mrgba=inputFrame.rgba();
firstTime++;
Mat roiHist=new Mat();
// set up the ROI for tracking
// implemented only one time
if(firstTime==2)
{
imgRoi=mrgba.submat(roi.x,roi.x+roi.width,roi.y,roi.y+roi.height);
Imgproc.cvtColor(imgRoi,mHsv, Imgproc.COLOR_BGR2HSV);//hsv'yi bul
Core.inRange(mHsv,new Scalar(0,60,32), new Scalar(180,255,255), mask);
roiHist=HistogramAndNormalize();
}
Imgproc.cvtColor(mrgba,mHsv, Imgproc.COLOR_BGR2HSV);
List<Mat> lHSV= Arrays.asList(mHsv);
Mat backproj = new Mat();
Imgproc.calcBackProject(lHSV, new MatOfInt(0, 1),roiHist, backproj,new MatOfFloat(0, 179, 0, 255), 1);
RotatedRect rect=Video.CamShift(backproj,roi, new TermCriteria(TermCriteria.EPS,10,1));
roi = rect.boundingRect();
Core.rectangle( mrgba,new org.opencv.core.Point(roi.x,roi.y),new org.opencv.core.Point(roi.x+roi.width,roi.y+roi.height),
new Scalar(0,255,0,255));
return mrgba;
}

How to create and display histogram in OpenCV4Android?

Can anybody tell me what am I doing wrong or give me example how to create AND DISPLAY histogram from grayscale mat in OpenCV4 Android? There is my code...
Vector<Mat> bgr_planes = new Vector<Mat>();
Core.split(cleanFaceMatGRAY, bgr_planes);
MatOfInt histSize = new MatOfInt(256);
final MatOfFloat histRange = new MatOfFloat(0f, 256f);
boolean accumulate = false;
Mat b_hist = new Mat();
Imgproc.calcHist(bgr_planes, new MatOfInt(0),new Mat(), b_hist, histSize, histRange, accumulate);
And then I try to set it to Image view to see it:
ivPickedPhoto.setImageBitmap(AppTools.createBitmapFromMat(b_hist, Bitmap.Config.ARGB_8888));
Method for display was created on my own:
public class AppTools {
public static Bitmap createBitmapFromMat(Mat mat, Bitmap.Config config) {
Bitmap bmp2 = null;
bmp2 = Bitmap.createBitmap(mat.cols(), mat.rows(), config);
Utils.matToBitmap(mat, bmp2);
return bmp2;
}
This gives me an error in the ivPickedPhoto(...) lane:
12-10 21:12:59.910: E/AndroidRuntime(10301): Caused by: CvException [org.opencv.core.CvException: /home/reports/ci/slave_desktop/50-SDK/opencv/modules/java/generator/src/cpp/utils.cpp:98: error: (-215) src.type() == CV_8UC1 || src.type() == CV_8UC3 || src.type() == CV_8UC4 in function void Java_org_opencv_android_Utils_nMatToBitmap2(JNIEnv*, jclass, jlong, jobject, jboolean)
I guess my problem is with the way I want to display the histogram... prolly I cant convert it to bmp. What is a good way to show histogram?

The OpenCV Java Documentation states that the Mat object you are passing should be of type CV_8UC1, CV_8UC3 or CV_8UC4. The documentation of calcHist doesn't really specify which type you should expect your b_Hist to be, but since it is complaining about the Mat type:
error: (-215) src.type() == CV_8UC1 || src.type() == CV_8UC3 || src.type() == CV_8UC4
you should probably convert it to either of the three above formats.