Segmentation fault when using cv2.ximgproc.ContourFitting

Python
1

I’d like to use cv2.ximgproc.ContourFitting for contours which is found by cv2.findContours but I can’t use it because it generate segmentation fault. The error message is only zsh: segmentation fault (core dumped) python3 test.py, so I’m out of idea. If you have any solution about this or you know what I should do next, I would appreciate it if you could let me know. Thank you.

command that I ran for installing opencv:

pipenv install opencv-python opencv-contrib-python

script:

import cv2
import sys

print(sys.version)
print(cv2.__version__)
print(cv2.getBuildInformation(), flush=True)

filepath = cv2.samples.findFile('pic1.png')
img = cv2.imread(filepath, cv2.IMREAD_GRAYSCALE)

_, mask = cv2.threshold(img, 127, 255, cv2.THRESH_BINARY_INV)
contours, _ = cv2.findContours(mask, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_NONE)

con1 = cv2.ximgproc.contourSampling(contours[0], 256)
con2 = cv2.ximgproc.contourSampling(contours[1], 256)

fit = cv2.ximgproc.ContourFitting(1024, 16)
fit.setFDSize(16)
alphaPhiST, dist = fit.estimateTransformation(con1, con2)

output:

3.10.4 (main, Sep  1 2022, 16:15:15) [GCC 8.5.0 20210514 (Red Hat 8.5.0-4)]
4.6.0

General configuration for OpenCV 4.6.0 =====================================
  Version control:               unknown

  Extra modules:
    Location (extra):            /io/opencv_contrib/modules
    Version control (extra):     unknown

  Platform:
    Timestamp:                   2022-06-07T10:28:32Z
    Host:                        Linux 5.13.0-1025-azure x86_64
    CMake:                       3.22.5
    CMake generator:             Unix Makefiles
    CMake build tool:            /bin/gmake
    Configuration:               Release

  CPU/HW features:
    Baseline:                    SSE SSE2 SSE3
      requested:                 SSE3
    Dispatched code generation:  SSE4_1 SSE4_2 FP16 AVX AVX2 AVX512_SKX
      requested:                 SSE4_1 SSE4_2 AVX FP16 AVX2 AVX512_SKX
      SSE4_1 (16 files):         + SSSE3 SSE4_1
      SSE4_2 (1 files):          + SSSE3 SSE4_1 POPCNT SSE4_2
      FP16 (0 files):            + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 AVX
      AVX (4 files):             + SSSE3 SSE4_1 POPCNT SSE4_2 AVX
      AVX2 (31 files):           + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 FMA3 AVX AVX2
      AVX512_SKX (5 files):      + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 FMA3 AVX AVX2 AVX_512F AVX512_COMMON AVX512_SKX

  C/C++:
    Built as dynamic libs?:      NO
    C++ standard:                11
    C++ Compiler:                /usr/lib/ccache/compilers/c++  (ver 10.2.1)
    C++ flags (Release):         -Wl,-strip-all   -fsigned-char -W -Wall -Wreturn-type -Wnon-virtual-dtor -Waddress -Wsequence-point -Wformat -Wformat-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Wsuggest-override -Wno-delete-non-virtual-dtor -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections  -msse -msse2 -msse3 -fvisibility=hidden -fvisibility-inlines-hidden -O3 -DNDEBUG  -DNDEBUG
    C++ flags (Debug):           -Wl,-strip-all   -fsigned-char -W -Wall -Wreturn-type -Wnon-virtual-dtor -Waddress -Wsequence-point -Wformat -Wformat-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Wsuggest-override -Wno-delete-non-virtual-dtor -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections  -msse -msse2 -msse3 -fvisibility=hidden -fvisibility-inlines-hidden -g  -O0 -DDEBUG -D_DEBUG
    C Compiler:                  /usr/lib/ccache/compilers/cc
    C flags (Release):           -Wl,-strip-all   -fsigned-char -W -Wall -Wreturn-type -Waddress -Wsequence-point -Wformat -Wformat-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wuninitialized -Wno-comment -Wno-strict-overflow -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections  -msse -msse2 -msse3 -fvisibility=hidden -O3 -DNDEBUG  -DNDEBUG
    C flags (Debug):             -Wl,-strip-all   -fsigned-char -W -Wall -Wreturn-type -Waddress -Wsequence-point -Wformat -Wformat-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wuninitialized -Wno-comment -Wno-strict-overflow -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections  -msse -msse2 -msse3 -fvisibility=hidden -g  -O0 -DDEBUG -D_DEBUG
    Linker flags (Release):      -Wl,--exclude-libs,libippicv.a -Wl,--exclude-libs,libippiw.a -L/root/ffmpeg_build/lib  -Wl,--gc-sections -Wl,--as-needed -Wl,--no-undefined  
    Linker flags (Debug):        -Wl,--exclude-libs,libippicv.a -Wl,--exclude-libs,libippiw.a -L/root/ffmpeg_build/lib  -Wl,--gc-sections -Wl,--as-needed -Wl,--no-undefined  
    ccache:                      YES
    Precompiled headers:         NO
    Extra dependencies:          /lib64/libopenblas.so Qt5::Test Qt5::Concurrent /usr/local/lib/libpng.so /lib64/libz.so Qt5::Core Qt5::Gui Qt5::Widgets Iconv::Iconv dl m pthread rt
    3rdparty dependencies:       libprotobuf ade ittnotify libjpeg-turbo libwebp libtiff libopenjp2 IlmImf quirc ippiw ippicv

  OpenCV modules:
    To be built:                 aruco barcode bgsegm bioinspired calib3d ccalib core cvv datasets dnn dnn_objdetect dnn_superres dpm face features2d flann fuzzy gapi hfs highgui img_hash imgcodecs imgproc intensity_transform line_descriptor mcc ml objdetect optflow phase_unwrapping photo plot python3 quality rapid reg rgbd saliency shape stereo stitching structured_light superres surface_matching text tracking video videoio videostab wechat_qrcode xfeatures2d ximgproc xobjdetect xphoto
    Disabled:                    world
    Disabled by dependency:      -
    Unavailable:                 alphamat cudaarithm cudabgsegm cudacodec cudafeatures2d cudafilters cudaimgproc cudalegacy cudaobjdetect cudaoptflow cudastereo cudawarping cudev freetype hdf java julia matlab ovis python2 sfm ts viz
    Applications:                -
    Documentation:               NO
    Non-free algorithms:         NO

  GUI:                           QT5
    QT:                          YES (ver 5.15.0 )
      QT OpenGL support:         NO
    GTK+:                        NO
    VTK support:                 NO

  Media I/O: 
    ZLib:                        /lib64/libz.so (ver 1.2.7)
    JPEG:                        libjpeg-turbo (ver 2.1.2-62)
    WEBP:                        build (ver encoder: 0x020f)
    PNG:                         /usr/local/lib/libpng.so (ver 1.6.37)
    TIFF:                        build (ver 42 - 4.2.0)
    JPEG 2000:                   build (ver 2.4.0)
    OpenEXR:                     build (ver 2.3.0)
    HDR:                         YES
    SUNRASTER:                   YES
    PXM:                         YES
    PFM:                         YES

  Video I/O:
    DC1394:                      NO
    FFMPEG:                      YES
      avcodec:                   YES (58.134.100)
      avformat:                  YES (58.76.100)
      avutil:                    YES (56.70.100)
      swscale:                   YES (5.9.100)
      avresample:                NO
    GStreamer:                   NO
    v4l/v4l2:                    YES (linux/videodev2.h)

  Parallel framework:            pthreads

  Trace:                         YES (with Intel ITT)

  Other third-party libraries:
    Intel IPP:                   2020.0.0 Gold [2020.0.0]
           at:                   /io/_skbuild/linux-x86_64-3.6/cmake-build/3rdparty/ippicv/ippicv_lnx/icv
    Intel IPP IW:                sources (2020.0.0)
              at:                /io/_skbuild/linux-x86_64-3.6/cmake-build/3rdparty/ippicv/ippicv_lnx/iw
    VA:                          NO
    Lapack:                      YES (/lib64/libopenblas.so)
    Eigen:                       NO
    Custom HAL:                  NO
    Protobuf:                    build (3.19.1)

  OpenCL:                        YES (no extra features)
    Include path:                /io/opencv/3rdparty/include/opencl/1.2
    Link libraries:              Dynamic load

  Python 3:
    Interpreter:                 /opt/python/cp36-cp36m/bin/python3.6 (ver 3.6.15)
    Libraries:                   libpython3.6m.a (ver 3.6.15)
    numpy:                       /opt/python/cp36-cp36m/lib/python3.6/site-packages/numpy/core/include (ver 1.13.3)
    install path:                python/cv2/python-3

  Python (for build):            /bin/python2.7

  Java:                          
    ant:                         NO
    JNI:                         NO
    Java wrappers:               NO
    Java tests:                  NO

  Install to:                    /io/_skbuild/linux-x86_64-3.6/cmake-install
-----------------------------------------------------------------

[ WARN:0@0.008] global /io/opencv/modules/core/src/utils/samples.cpp (61) findFile cv::samples::findFile('pic1.png') => '/home/*****/tools/opencv-4.6.0/samples/data/pic1.png'
zsh: segmentation fault (core dumped)  python3 test.py
2

What you should do next is what you should always do: when you think you have an array and want to access its elements, check that the creation of that array succeeded and that the elements actually exist…

3

Thank you for your help. Excuse me, but I am a beginner for programming and I don’t know which array I should check. For simplicity, I didn’t check len(contours) >= 2 in the example script but I already checked it in my own script and I verified it is true. Is there any other variable to check?

4

input data please, so we can reproduce the issue.

5

This is the input data.
pic1

6

can you try fourier_descriptor_demo.py?

7

you forget create in your code :

fit = cv.ximgproc.createContourFitting(1024, 16)
fit.setFDSize(16)
8

The cause was a trivial mistake of forgetting to create. I’m really glad it was resolved. Thank you very much!

As a side note, if I change line 162 to the following, then fourier_descriptor_demo.py will work.

    dst = cv.ximgproc.transformFD(ctrRot2d, alphaPhiST, fdContour=False);