HOGDescriptor.compute doesn't work

[tomaszkalisiak-digica]

The method has three overloads that I tried out.

public native void compute(@ByVal Mat img,
                             @StdVector float[] descriptors);
public native void compute(@ByVal Mat img,
                             @StdVector FloatBuffer descriptors);
public native void compute(@ByVal Mat img,
                             @StdVector FloatPointer descriptors);

I also have this line

var descriptorSize = (int) hog.getDescriptorSize(); // 576

I tried the following:

var arr = new float[descriptorSize];
hog.compute(image, arr);

and

var features = new FloatPointer(descriptorSize);
hog.compute(image, features);

and

var features = new FloatPointer(descriptorSize);
var hogMat = new Mat(1, descriptorSize, CV_32FC1, features);
hog.compute(image, hogMat.getFloatBuffer());

I always get one of those errors:

free(): invalid next size (normal)
Aborted (core dumped)

or

corrupted size vs. prev_size
Aborted (core dumped)

or

#
# A fatal error has been detected by the Java Runtime Environment:
#
#  SIGSEGV (0xb) at pc=0x00007fcbfe60bc8e, pid=234668, tid=234669
#
# JRE version: OpenJDK Runtime Environment Temurin-17.0.7+7 (17.0.7+7) (build 17.0.7+7)
# Java VM: OpenJDK 64-Bit Server VM Temurin-17.0.7+7 (17.0.7+7, mixed mode, tiered, compressed oops, compressed class ptrs, g1 gc, linux-amd64)
# Problematic frame:
# C  [libopencv_objdetect.so.407+0x6bc8e]
#
# Core dump will be written. Default location: /mnt/wslg/dumps/core.%e.234668
#
# An error report file with more information is saved as:
# /home/bobini/JavaCV-test-wsl/hs_err_pid234668.log
#
# If you would like to submit a bug report, please visit:
#   https://github.com/adoptium/adoptium-support/issues
# The crash happened outside the Java Virtual Machine in native code.
# See problematic frame for where to report the bug.
#
Aborted (core dumped)

I load my hog descriptor from an xml, I made it in Python with opencv-python 4.7.0.68. It works in my C++ project, which uses OpenCV 4.5.5, so I think it's fine. I also load an SVM model and that one works fine.

Is it possible to use HOGDescriptor.compute in any way?

[tomaszkalisiak-digica]

I rewrote my xml into a constructor:

private final HOGDescriptor hog = new HOGDescriptor(new Size(64, 64), new Size(8, 8), new Size(8, 8),
            new Size(8, 8), 9, 0, 2.0, 0, 0.2, true, 64, true);

Feel free to test with this.

[saudet]

Could you provide a working example in C++? Just the constructor + compute is fine.

[tomaszkalisiak-digica]

Turns out that the input image wasn't resized to the right size. There was no assert for that inside OpenCV, it just crashed.

[saudet]

Please report upstream! https://github.com/opencv/opencv/issues