CODEWITHSUNDEEP
c++opencvimage-processingconvolution
Lamar Latrell
Lamar Latrell

Reputation: 1669

Using custom kernel in opencv 2DFilter - causing crash ... convolution how?

Thought I'd try my hand at a little (auto)correlation/convolution today in openCV and make my own 2D filter kernel.

Following openCV's 2D Filter Tutorial I discovered that making your own kernels for openCV's Filter2D might not be that hard. However I'm getting unhandled exceptions when I try to use one.

Code with comments relating to the issue here:

#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
#include <stdlib.h>
#include <stdio.h>
#include <iostream>

using namespace cv;
using namespace std;

int main(int argc, char** argv) {

    //Loading the source image
    Mat src;
    src = imread( "1.png" );

    //Output image of the same size and the same number of channels as src.
    Mat dst;
    //Mat dst = src.clone();   //didn't help...

    //desired depth of the destination image
    //negative so dst will be the same as src.depth()
    int ddepth = -1;        

    //the convolution kernel, a single-channel floating point matrix:
    Mat kernel = imread( "kernel.png" );
    kernel.convertTo(kernel, CV_32F);     //<<not working
    //normalize(kernel, kernel, 1.0, 0.0, 4, -1, noArray());  //doesn't help

    //cout << kernel.size() << endl;  // ... gives 11, 11

    //however, the example from tutorial that does work:
    //kernel = Mat::ones( 11, 11, CV_32F )/ (float)(11*11);

    //default value (-1,-1) here means that the anchor is at the kernel center.
    Point anchor = Point(-1,-1);

    //value added to the filtered pixels before storing them in dst.
    double delta = 0;

    //alright, let's do this...
    filter2D(src, dst, ddepth , kernel, anchor, delta, BORDER_DEFAULT );

    imshow("Source", src);     //<< unhandled exception here
    imshow("Kernel", kernel);
    imshow("Destination", dst);
    waitKey(1000000);

    return 0;
}

As you can see, using the tutorials kernel works fine, but my image will crash the program, I've tried changing the bit-depth, normalizing, checking size and lots of commenting out blocks to see where it fails, but haven't cracked it yet.

The image is, '1.png':

1.png

And the kernel I want 'kernel.png':

kernel.png

I'm trying to see if I can get a hotspot in dst at the point where the eye catchlight is (the kernel I've chosen is the catchlight). I know there are other ways to do this, but I'm interested to see how effective convolving the catchlight over itself is. (autocorrelation I think that's called?)

Direct questions:

Thanks in advance for any help :)

Upvotes: 0

Views: 2260

Answers (1)

sriram
sriram

Reputation: 411

The assertion error should be posted which would help someone to answer you other than questioning why is the crash. Anyways, I have posted below the possible errors and solution for convolution filter2D.

Error 1:

OpenCV Error: Assertion failed (src.channels() == 1 && func != 0) in cv::countNo nZero, file C:\builds\2_4_PackSlave-win32-vc12-shared\opencv\modules\core\src\st at.cpp, line 549

Solution : Your input Image and the kernel should be grayscales. You can use the flag 0 in imread. (ex. cv::imread("kernel.png",0) to read the image as grayscale.) If you want to apply different kernels to different channels, split the image into separate color planes using split() and process them individually.

I don't see anything other than the obove error that may crash. Kernel size should in odd numbers and your kernel image is 11X11 which is fine. If it stills crashes kindly provide more information in order to help you out.

Upvotes: 2

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