Segmentation fault when using cv2.ximgproc.ContourFitting

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, 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


import cv2
import sys

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)
alphaPhiST, dist = fit.estimateTransformation(con1, con2)


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

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

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

    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

    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/ Qt5::Test Qt5::Concurrent /usr/local/lib/ /lib64/ 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/ (ver 1.2.7)
    JPEG:                        libjpeg-turbo (ver 2.1.2-62)
    WEBP:                        build (ver encoder: 0x020f)
    PNG:                         /usr/local/lib/ (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/
    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

    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

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…

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?

input data please, so we can reproduce the issue.

This is the input data.

can you try

you forget create in your code :

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

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 will work.

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