将 Mat 转换为 Bitmap 会导致错误

Question

我正在使用 OpenCV4Android 2.4.11 版，我正在尝试检测图像中的角点。为此，我正在使用 Harris corner detector.the 我面临的问题是，在检测到图像中的角之后，如下所示在代码中，我想在将其转换为位图后显示包含检测到的角的图像，但随后我收到以下错误消息。

第 1 步和第 2 步执行时没有错误，但是当我运行第 3 步时，我收到发布的 logcat 错误。

请让 mek 知道我收到此错误的原因以及解决方法？

代码:

//step 1
this.mMatGray = new Mat();
Imgproc.cvtColor(this.mMatInputFrame, this.mMatGray, Imgproc.COLOR_BGR2GRAY);

//step 2
Imgproc.cornerHarris(mMatGray,mMatGray,3,3,3,1);

//step 3
final Bitmap bitmap = Bitmap.createBitmap(mMatInputFrame.cols(), mMatInputFrame.rows(), Bitmap.Config.ARGB_8888);
Utils.matToBitmap(mMatGray, bitmap);
getActivity().runOnUiThread(new Runnable() {
@Override
public void run() {
mIVEdges.setImageBitmap(bitmap);
    }
});

错误:

OpenCV Error: Assertion failed (src.type() == CV_8UC1 || src.type() == CV_8UC3 || src.type() == CV_8UC4) 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 98
E/org.opencv.android.Utils: nMatToBitmap catched cv::Exception: /hdd2/buildbot/slaves/slave_ardbeg1/50-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)
E/AndroidRuntime: FATAL EXCEPTION: Thread-2477
Process: com.example.cornerdetection_00, PID: 22407
CvException [org.opencv.core.CvException: /hdd2/buildbot/slaves/slave_ardbeg1/50-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)
]
at org.opencv.android.Utils.nMatToBitmap2(Native Method)
at org.opencv.android.Utils.matToBitmap(Utils.java:123)
at org.opencv.android.Utils.matToBitmap(Utils.java:132)
at com.example.cornerdetection_00.FragOpenCVCam.cornerHarris(FragOpenCVCam.java:204)
at com.example.cornerdetection_00.FragOpenCVCam.onCameraFrame(FragOpenCVCam.java:159)
at org.opencv.android.CameraBridgeViewBase.deliverAndDrawFrame(CameraBridgeViewBase.java:387)
at org.opencv.android.JavaCameraView$CameraWorker.run(JavaCameraView.java:346)

更新1:

现在在测试 "MIkka Marmik" 提供的以下代码后，我收到以下错误

代码:

Mat mMatGray = new Mat();
Imgproc.cvtColor(mMatGray, mMatGray, Imgproc.COLOR_BGR2GRAY);
//step 2
Imgproc.cornerHarris(mMatGray,mMatGray,3,3,3,1);
//step 3
final Bitmap bitmap = Bitmap.createBitmap(mMatGray.cols(), mMatGray.rows(), Bitmap.Config.ARGB_8888);
Utils.matToBitmap(mMatGray, bitmap);

错误:

OpenCV Error: Assertion failed (scn == 3 || scn == 4) in void cv::cvtColor(cv::InputArray, cv::OutputArray, int, int), file /hdd2/buildbot/slaves/slave_ardbeg1/50-SDK/opencv/modules/imgproc/src/color.cpp, line 3739
E/org.opencv.imgproc: imgproc::cvtColor_11() caught cv::Exception: /hdd2/buildbot/slaves/slave_ardbeg1/50-SDK/opencv/modules/imgproc/src/color.cpp:3739: error: (-215) scn == 3 || scn == 4 in function void cv::cvtColor(cv::InputArray, cv::OutputArray, int, int)
E/AndroidRuntime: FATAL EXCEPTION: Thread-4693

Answer 1

试试这个

   Mat mMatGray = new Mat();
    mMatGray = Highgui.imread(path);
    Imgproc.cvtColor(mMatGray, mMatGray, Imgproc.COLOR_RGB2BGR);
    Imgproc.cvtColor(mMatGray, mMatGray, Imgproc.COLOR_BGR2GRAY);
    //step 2
  Imgproc.cornerHarris(mMatGray,mMatGray,3,3,3,1);
  Core.normalize(mMatGray, mMatGray, 0, 255, Core.NORM_MINMAX, CvType.CV_32FC1, new Mat());
  Core.convertScaleAbs(mMatGray, mMatGray);
//step 3
  final Bitmap bitmap = Bitmap.createBitmap(mMatGray.cols(), mMatGray.rows(), Bitmap.Config.ARGB_8888);
 Utils.matToBitmap(mMatGray, bitmap);

Answer 2

createBitmap 方法需要一个 1,3 或 4 通道的图像。您必须将输出 mMatGray 转换为 createBitmap 方法所需的格式。但是，在检查了 Harris 角点算法的 OpenCV documentation 之后，还需要执行几个步骤来设置图像以进行角点检测。试试这个：

Mat src_gray        = new Mat();
Mat dst             = new Mat();
Mat dst_norm        = new Mat();
Mat dst_norm_scaled = new Mat();

// Detector parameters
int blockSize = 2;
int apertureSize = 3;
double k = 0.04;
// Filter params
int thresh = 200;
int max_thresh = 255;

// Detecting corner
Imgproc.cvtColor(src, src_gray, Imgproc.COLOR_BGR2GRAY);
Imgproc.cornerHarris(src_gray, dst, blockSize, apertureSize, k);

// Normalizing
Core.normalize(dst, dst_norm, 0, 255, Core.NORM_MINMAX);
Core.convertScaleAbs(dst_norm, dst_norm_scaled);

// Drawing a circle around corners
for (int j = 0; j < dst_norm.rows(); j++) {
    for (int i = 0; i < dst_norm.cols(); i++) {
        if (dst_norm.get(j, i)[0] > thresh) {
            Core.circle(dst_norm_scaled, new Point(i, j), 5, new Scalar(255));
        }
    }
}

// Create bitmap
final Bitmap bitmap = Bitmap.createBitmap(dst_norm_scaled.cols(), dst_norm_scaled.rows(), Bitmap.Config.ARGB_8888);
Utils.matToBitmap(dst_norm_scaled, bitmap);

将 Mat 转换为 Bitmap 会导致错误

converting a Mat into Bitmap causes an error

android

opencv

bitmap

opencv4android

corner-detection