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imshow() sometimes don't clear previous image

asked 2017-08-29 00:56:57 -0500

salman gravatar image

updated 2017-08-29 10:30:56 -0500

 #include <opencv2/highgui/highgui.hpp>
#include <iostream>
#include <stdio.h>
#include <string>
using namespace cv;
using namespace std;

int main()
{
    String folder = "F:/8TH SEMESTER/Traffic Sign Dectection/30speed/*.ppm";
    //string folder = ("F:/Hammad Profile/FYP/German/GTSDB/FullIJCNN2013/*.ppm");
    vector<String> filenames;

    glob(folder, filenames);

    Mat myImage;

    for (size_t i = 0; i < filenames.size(); i++)
    {
        myImage = imread(filenames[i]);
        imshow("Sample Traffic signs", myImage);
        int c = cv::waitKey(400);
    }

    return 0;
}

"For example if 1st image is display and then 2nd so it display it but some portion of 1st image is show. why this happen.

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"but some portion of 1st image is show. " -- this is unclear

berak gravatar imageberak ( 2017-08-29 03:38:45 -0500 )edit
1

when small images (having different width and height ) displayed in same window consecutively, sometimes some part of previous image still visible on window.question is connected with other question http://answers.opencv.org/question/17... i will merge two questions into one later.

sturkmen gravatar imagesturkmen ( 2017-08-29 09:27:27 -0500 )edit

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answered 2017-08-29 09:24:34 -0500

updated 2017-08-29 10:11:14 -0500

this is not a serious problem but you can avoid it by using destroyWindow() or destroyAllWindows() before imshow()

TEST CODE:

#include <opencv2/highgui/highgui.hpp>

using namespace cv;

int main()
{   
    Mat m1(50, 100, CV_8UC3, Scalar(255, 0, 0));
    Mat m2(100, 50, CV_8UC3, Scalar(0, 0, 255));

    imshow("test", m1);
    waitKey(0);
    imshow("test", m2);
    waitKey(0); 

    imshow("test", m1);
    waitKey(0);
    destroyWindow("test"); // or    destroyAllWindows();
    imshow("test", m2);
    waitKey(0);

    return 0;
}

image description ......... image description

image description ......... image description

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can someone try this code on linux environment? i wonder if this problem exist on linux

sturkmen gravatar imagesturkmen ( 2017-08-29 10:32:48 -0500 )edit
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Asked: 2017-08-29 00:56:57 -0500

Seen: 5,893 times

Last updated: Aug 29 '17