Return RGB values of the the current Pixel ?

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asked 2013-02-18 11:43:19 -0600

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How to return the RGB values of the current Pixel i stop on it by the mouse cursor??

My Code:

#include <opencv\cv.h>
#include <opencv\highgui.h>
#include <iostream>

void mouseEvent(int evt, int x, int y, int flags, void* param){
    evt==CV_EVENT_MOUSEMOVE;
    printf("Current Position: x= %d y= %d\n",x,y);
}

int main() 
{
cvNamedWindow("rgb"); 
CvCapture*capture =cvCaptureFromCAM(0);
IplImage* rgb ;

while(1){
rgb= cvQueryFrame( capture ); 
cvShowImage("rgb",rgb);
cvSetMouseCallback("rgb",  mouseEvent, 0);



char c = cvWaitKey(33);
if( c == 27 ) break;
}

cvReleaseCapture( &capture );
cvDestroyWindow( "rgb" );

}

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answered 2013-02-18 12:08:10 -0600

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You need to pass your image as a parameter to the callback and read it from the image. Please read the tutorials on docs.opencv where a clear explanation about accessing pixel values is described!

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answered 2013-02-18 13:20:36 -0600

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change your code:

IplImage* rgb ;
void mouseEvent(int evt, int x, int y, int flags, void* param)
{
    evt==CV_EVENT_MOUSEMOVE;
    char* data = rgb->imageData + rgb->widthStep * y + x * 3;
    printf("Current Position: x= %d y= %d B=%d G=%d R=%d\n",x,y,data[0],data[1],data[2]);
}

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you can type cast IplImage as void and pass it to the function, That way you dont need to have it as global

benzun ( 2013-02-18 23:42:25 -0600 )edit

Does not matter.It is also true method.

Mostafa Sataki ( 2013-02-19 03:09:59 -0600 )edit

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answered 2013-02-18 23:48:44 -0600

This post is a wiki. Anyone with karma >50 is welcome to improve it.

void mouseEvent(int evt, int x, int y, int flags, void* param)
{
    IplImage* rgb = (IplImage*) param;
    if(evt==CV_EVENT_MOUSEMOVE)
    {
          char* data = rgb->imageData + rgb->widthStep * y + x * 3;
          printf("Current Position: x= %d y= %d B=%d G=%d R=%d\n",x,y,data[0],data[1],data[2]);
    }
}


void main()
{
    IplImage *image;
.... load image....
     cvSetMouseCallback(name, my_mouse_callback, (void*) image);
}

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Return RGB values of the the current Pixel ?

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Return RGB values of the the current Pixel ?