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Editorial Team
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Asked: 2026-05-31T10:13:25+00:00

I am using openCV function cvPutText, but it seems it won’t execute or it

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I am using openCV function cvPutText, but it seems it won’t execute or it is quickly overwritten. Here is my block of code:

          ...
if(showResult==1){

        cvNamedWindow("Znak", CV_WINDOW_AUTOSIZE);
        cvShowImage("Znak", znak);

        if(result == 0){
            ascii_result = "A";
            cvSet(znak, cvScalar(26,26,26));
            cvPutText(znak, "A", cvPoint(13, 185), &font, cvScalar(255, 166, 44, 0));
            printf("A working");
        }
        if(result == 1){
            ascii_result = "B";
            cvSet(znak, cvScalar(26,26,26));
            cvPutText(znak, "B", cvPoint(13, 185), &font, cvScalar(255, 166, 44, 0));
            printf("B working");
        }
          ...

It isn’t in any loop. The problem is, that the window “Znak” is created, but cvSet() and cvPutText won’t execute or are overwritten…so I only see blank window with its deafult gray color

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1 Answer

  1. Editorial Team

    CvShowImage should be put every time you made change to the image and want to show it.

          ...
    if(showResult==1){

    cvNamedWindow("Znak", CV_WINDOW_AUTOSIZE);
    cvShowImage("Znak", znak);

    if(result == 0){
        ascii_result = "A";
        cvSet(znak, cvScalar(26,26,26));
        cvPutText(znak, "A", cvPoint(13, 185), &font, cvScalar(255, 166, 44, 0));
        cvShowImage("Znak", znak);
        printf("A working");
    }
    if(result == 1){
        ascii_result = "B";
        cvSet(znak, cvScalar(26,26,26));
        cvPutText(znak, "B", cvPoint(13, 185), &font, cvScalar(255, 166, 44, 0));
        cvShowImage("Znak", znak);
        printf("B working");
    }
      ...

    When you call cvShowImage it sends a copy of the image to the window. If you change the image in your code it will not change in the window, since it’s just a copy of an older image.

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