OpenCV error: Assertion failed on iOS

Question

I'm trying to find the largest blob in an image and classify it according to a linked plist file. I'm using the latest version of OpenCV for iOS, and I've looked at several related questions, but none so far relate to iOS.

I'm getting this error:

OpenCV Error: Assertion failed (type == src2.type() && src1.cols == src2.cols && (type == CV_32F || type == CV_8U)) in batchDistance, file /Users/admin/Desktop/OpenCV/modules/core/src/stat.cpp, line 4000

libc++abi.dylib: terminating with uncaught exception of type cv::Exception: /Users/admin/Desktop/OpenCV/modules/core/src/stat.cpp:4000: error: (-215) type == src2.type() && src1.cols == src2.cols && (type == CV_32F || type == CV_8U) in function batchDistance

when I run this:

- (IBAction)CaptureButton:(id)sender
  {
       // Find the biggest blob.
       int biggestBlobIndex = 0;
       for (int i = 0, biggestBlobArea = 0; i < detectedBlobs.size(); i++)
       {
          Blob &detectedBlob = detectedBlobs[i];
          int blobArea = detectedBlob.getWidth() * detectedBlob.getHeight();
          if (blobArea > biggestBlobArea)
          {
              biggestBlobIndex = i;
              biggestBlobArea = blobArea;
          }
       }

       Blob &biggestBlob = detectedBlobs[biggestBlobIndex];

       // Classify the blob.
       blobClassifier->classify(biggestBlob); // the error occurs here
  }

The classify that I'm calling in the last line there was declared in another file:

void classify(Blob &detectedBlob) const;

This is the relevant code from stat.cpp:

Mat src1 = _src1.getMat(), src2 = _src2.getMat(), mask = _mask.getMat();
int type = src1.type();

CV_Assert( type == src2.type() && src1.cols == src2.cols &&
           (type == CV_32F || type == CV_8U)); // this is line 4000

What's the issue here?

assertion failed for one of the listed properties. find out which one, why and fix that. you know what a debugger is? — Piglet
@Piglet Yes, but I'm unsure as to how to find the property that is causing the error. — fi12
You could add a break point befor line 3934 in stat.cpp and see the values. — Piglet
@Piglet The issue is that stat.cpp isn't in this Xcode project; it's in the same directory as the OpenCV framework is. When I place a breakpoint on the relevant line, nothing happens, because they're not in the same project together. — fi12

morynicz morynicz · Accepted Answer · 2017-08-08T19:52:15

I don't know how do cv::Mat objects look in objective c, but You need to make sure that all the dimensions, channel number and depth of images used with the classifier are uniform. Probably there was a step previously when You fed the classifier with training images. Maybe one of them is not compatible with the mat that You are trying to classify.

You can try debugging with opencv if You compile it Yourself and set debug version in CMake.

OpenCV error: Assertion failed on iOS

1 Answers