android opencv findcontours() unsupported format exception

Question

I am trying to write an android app that allows for realtime processing of camera feed from a device to detect contours. Despite following many examples online, when I run the following code, an exception is thrown (also shown below).

Code:

Bitmap image = mTextureView.getBitmap();
Mat mat = new Mat();
Mat matConverted = new Mat();
Utils.bitmapToMat(image, mat);
mat.convertTo(matConverted, CvType.CV_32SC1);
List<MatOfPoint> contours = new ArrayList<>();
Imgproc.findContours(matConverted, contours, new Mat(), Imgproc.RETR_FLOODFILL, 
    Imgproc.CHAIN_APPROX_SIMPLE);

Exception:

CvException [org.opencv.core.CvException: cv::Exception:
/Volumes/Linux/builds/master_pack-android/opencv/modules/imgproc/src/contours.cpp:198:
error: (-210) [Start]FindContours supports only CV_8UC1 images when mode !=
CV_RETR_FLOODFILL otherwise supports CV_32SC1 images only in function _CvContourScanner* 
cvStartFindContours(void*, CvMemStorage*, int, int, int, CvPoint)

Am I missing something obvious here?

The error message says it all. The image supplied to findContours must be 1-channel 8-bit image. Yours is 32-bit. — hiroki
– hiroki, Commented Jan 5, 2017 at 2:19

Sefat Noor Orni · Accepted Answer · 2017-06-18 01:41:21Z

1

Try

Mat matConverted = new Mat(mat.size(), CvType.CV_8UC1);

In my case, it worked

answered Jun 18, 2017 at 1:41

Sefat Noor Orni

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