segfault on cv::imshow("Image window", cv_ptr->image)

asked 2014-06-15 05:56:18 -0600

hvn
1 ●1 ●3

updated 2014-06-16 14:43:30 -0600

Hi,

When I try to show an image with

cv_ptr->image.data = image_in_mat.data;
cv::namedWindow("Image window");
cv::imshow("Image window", cv_ptr->image);

I get a segfault on the last line while it compiles fine. The segfault tells it's a memory issue but why ?

Ok, I tried many things now and I have this piece of code and 2 points of failure (imshow and publish) I don't get:

try
{
    cv::imshow(OPENCV_WINDOW, cv_ptr->image);
}
catch (cv::Exception& cv_ex)
{
    ROS_ERROR("cv exception: %s", cv_ex.what());
    return;
}
cv::waitKey(0);
image_pub.publish(cv_ptr->toImageMsg());

Why are these causing segfaults ?

answered 2014-06-16 21:54:11 -0600

unxnut

1644 ●4 ●9 ●28 http://www.cs.umsl.edu...

Seems to me that you are not copying all the properties of image_in_mat into cv_ptr->image. Assuming that both of them are of type cv::Mat, you can try to do the following:

cv_ptr->image = image_in_mat;
cv::imshow ( "Image window", cv_ptr->image );

and see if that cause the seg fault. If that does not, your headers are not correct in the current implementation.

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Thanks, that solved the segfaults and after switching image_in_mat and cv_ptr->image it works..

hvn ( 2014-06-17 01:02:59 -0600 )edit

That implies that your header do not match the data. You may have to investigate the step size and other properties.

unxnut ( 2014-06-17 06:40:10 -0600 )edit

i have the same problem, what did you do exactly to fix it.

chetan3061 ( 2015-04-15 23:48:01 -0600 )edit

Can you show detail specific to your issue?

unxnut ( 2015-04-16 06:38:21 -0600 )edit

this is what i used and it gave me the segmentation fault

void callback(const sensor_msgs::ImageConstPtr& msg) {

Mat mat;

cv_bridge::CvImagePtr cvImagePtr; try {

    cvImagePtr = cv_bridge::toCvCopy(msg,sensor_msgs::image_encodings::BGR8);

     mat = cvImagePtr->image;

    //std::cout<<mat.rows<<"\n";


     } 

catch (cv_bridge::Exception &e) {

   ROS_ERROR("cv_bridge exception:  %s", e.what());

}

    imshow("windowName", cvImagePtr->image);

    cv::waitKey(3);

    destroyWindow("windowName");

}

chetan3061 ( 2015-04-16 15:52:59 -0600 )edit

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