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Possible solutions for OpenCv Assertion Error problem

asked 2013-09-25 23:41:27 -0500

utkarshmankad gravatar image

updated 2013-09-26 01:37:03 -0500

berak gravatar image

I am trying to write a simple module for Image Cropping - here's my code

cv::Mat img = input_frame;
cv::Mat finalImg;

// Set Region of Interest to the area defined by the box
int h = input_frame.rows;
int w = input_frame.cols;

cv::Rect roi(skeletonBound[0].x,skeletonBound[0].y,abs(skeletonBound[3].x - skeletonBound[0].x),abs(skeletonBound[3].y - skeletonBound[0].y));

if(!(roi.height <= h) && !(roi.width <= w))
{

    return -1;
}
else
{
    cv::Mat crop = input_frame(roi);
    cv::imshow("crop", crop);
    cv::imwrite("cropped.png", crop);
    cv::Mat finalImg(crop);

    finalImageToBeusedForDetection = finalImg; 
    cout << "Success : "; 
    return 1;
}

I am getting this error -

image description

I checked and rechecked the dimensions, they are correct. i am successfully able to run this code for about early 10-15 frames, later at certain point of time, the code crashes abruptly with above error log. There seems to be a very small problem which i am not able to figure out.

Previously, I was also getting the error where ROI was greater than the size of input image. In that scenario also, the above code worked fine for first 10-15 frames, and later it crashed. I couldn't figure out the problem and hence discarded the erroneous result frame.

I am using latest versions of OpenCv for C++ in Visual studio 2012.

Please help me out on this. I tried all web resources, and have spent pretty lot of time on the same.

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Comments

This assertion error somehow indicates that size of your matrix is corrupted. Also, you did not post the whole code snippet for cropping, right? Using Mat frame_copy = frame; can be sometimes a little tricky simply because you create a new frame_copy header that points to the same image as frame header. So if you make changes on frame_copy that means that frame will be affected too. So if your aim is to copy the data you need to use frame.copyTo(frame_copy).

Vladimir Cernega gravatar imageVladimir Cernega ( 2013-09-26 01:35:39 -0500 )edit

Thanks Vladimir, I made the changes in my code as you mentioned. I got a slight improvement in performance, but the problem still persists. The cropping is just a small part of the whole functionality. Hence i didn't paste the code involving the dependency.

utkarshmankad gravatar imageutkarshmankad ( 2013-09-26 01:54:45 -0500 )edit

I am checking the ROI creation line.

utkarshmankad gravatar imageutkarshmankad ( 2013-09-26 01:55:16 -0500 )edit

2 answers

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answered 2013-09-26 02:24:58 -0500

utkarshmankad gravatar image

Thank you very very much. I was successfully able to solve the problem. As per suggestion given by Vladislav Vinogradov and Moster, i modified my earlier condition to check the ROI. The new condition is as follows -

if(roi.x >= 0 && roi.y >= 0 && roi.width + roi.x < input_frame.cols && roi.height + roi.y < input_frame.rows)
{
    // your code

}
else
    return -1;

The assert problem is successfully solved here. Thanks a lot Moster and Vladislav Vinogradov.

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answered 2013-09-26 01:41:49 -0500

Vladislav Vinogradov gravatar image

Check that roi is correct:

if (roi.x >= 0 && row.y >= 0 && roi.width < input_frame.cols && roi.height < input_frame.rows)
{
    // your code
}
else
{
    return -1;
}
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Comments

This will probably still not be successful. It could happy that roi.width < img.cols, but it will still fail. This happens when roi.x + roi.width > img.cols. So the check should be roi.x + roi.width < img.cols and the same for the height. Thats also what the assert says.

Moster gravatar imageMoster ( 2013-09-26 01:46:10 -0500 )edit
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Asked: 2013-09-25 23:41:27 -0500

Seen: 9,652 times

Last updated: Sep 26 '13