FAQ
Hi,

I am trying to set some parameters for FeatureDetector and have checked the
post
https://groups.google.com/forum/?fromgroups#!searchin/android-opencv/hessianThreshold/android-opencv/-1mXlMNOudI/Tp8LKjQRGCkJ.


However the program stops at the detector.read(filename) and in LogCat I
find the message "Fatal signal 11 (SIGSEGV) at 0x00000000 (code=1) ...

Can anyone help me to solve this problem?

Also can someone tell me what are the default parameters for SURF
FeatureDetector and DescriptorExtractor?

Thanks

David

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  • David at Aug 3, 2012 at 2:58 pm
    I debugged the code and find that when I instantiate FeatureDetector with
    FeatureDetector.create(FeatureDetector.SURF). The "nativeObj" is assigned
    to addr 0. That probably is the key issue. Any help with that?

    Thanks
    On Thursday, August 2, 2012 10:42:10 AM UTC-4, David wrote:

    Hi,

    I am trying to set some parameters for FeatureDetector and have checked
    the post
    https://groups.google.com/forum/?fromgroups#!searchin/android-opencv/hessianThreshold/android-opencv/-1mXlMNOudI/Tp8LKjQRGCkJ.


    However the program stops at the detector.read(filename) and in LogCat I
    find the message "Fatal signal 11 (SIGSEGV) at 0x00000000 (code=1) ...

    Can anyone help me to solve this problem?

    Also can someone tell me what are the default parameters for SURF
    FeatureDetector and DescriptorExtractor?

    Thanks

    David
    --
  • Andrey Pavlenko at Aug 3, 2012 at 3:20 pm
    The patented content ('nonfree' module, e.g. SURF, SIFT) was removed from
    OpenCV4Android SDK.
    Looks like it was removed a bit inaccurately, so instead of throwing an
    exception it returns invalid object.

    Could you use ORB instead? (with DescriptorMatcher.BRUTEFORCE_HAMMING)

    --
  • David at Aug 3, 2012 at 3:32 pm
    Hi Andrey,

    I have used SURF to train my images on my PC so I need to use it on
    android. Would you add the nonfree module back? Or if I still want to use
    SURF, what should I do?

    Thanks

    David
    On Friday, August 3, 2012 11:20:25 AM UTC-4, Andrey Pavlenko wrote:

    The patented content ('nonfree' module, e.g. SURF, SIFT) was removed from
    OpenCV4Android SDK.
    Looks like it was removed a bit inaccurately, so instead of throwing an
    exception it returns invalid object.

    Could you use ORB instead? (with DescriptorMatcher.BRUTEFORCE_HAMMING)
    --
  • Rui Marques at Aug 14, 2012 at 2:05 pm
    Maybe you can get by using the latest OpenCV4Android which still has the
    nonfree module included, I think it is version 2.4.1 but i am not sure.

    Also, if you really want the latest version, you can probably compile it
    from source AND include the nonfree module - instead of using the already
    built package that you have downloaded.
    I am not sure if this is possible, maybe Andrey can confirm.

    Instructions on how to compile OpenCV4Android from source are somewhere on
    the documentation site - http://opencv.org/documentation.html .
    On Friday, 3 August 2012 16:32:43 UTC+1, David wrote:

    Hi Andrey,

    I have used SURF to train my images on my PC so I need to use it on
    android. Would you add the nonfree module back? Or if I still want to use
    SURF, what should I do?

    Thanks

    David
    On Friday, August 3, 2012 11:20:25 AM UTC-4, Andrey Pavlenko wrote:

    The patented content ('nonfree' module, e.g. SURF, SIFT) was removed from
    OpenCV4Android SDK.
    Looks like it was removed a bit inaccurately, so instead of throwing an
    exception it returns invalid object.

    Could you use ORB instead? (with DescriptorMatcher.BRUTEFORCE_HAMMING)
    --
  • Andrey Pavlenko at Aug 14, 2012 at 3:12 pm
    Yes, OpenCV4Android can be re-built locally with 'nonfree' module included.
    An outdated instruction is here:
    http://code.opencv.org/projects/opencv/wiki/Building_OpenCV4Android_from_trunk (to
    be updated soon).
    After a successful build one more step is required: "make install" in the
    build folder, then you'll have SDK-like structure in 'install' folder.

    We're not going to include 'nonfree' stuff to OpenCV binary packages for
    Google Market, but we'll consider adding it to SDK in future to allow to
    include it to app APK...

    --
  • Dawei Li at Aug 14, 2012 at 3:22 pm
    That helps a lot. Thanks
    On Tue, Aug 14, 2012 at 11:12 AM, Andrey Pavlenko wrote:

    Yes, OpenCV4Android can be re-built locally with 'nonfree' module included.
    An outdated instruction is here:
    http://code.opencv.org/projects/opencv/wiki/Building_OpenCV4Android_from_trunk (to
    be updated soon).
    After a successful build one more step is required: "make install" in the
    build folder, then you'll have SDK-like structure in 'install' folder.

    We're not going to include 'nonfree' stuff to OpenCV binary packages for
    Google Market, but we'll consider adding it to SDK in future to allow to
    include it to app APK...

    --


    --

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