Return RGB values of the the current Pixel ?

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deprecated

asked Feb 18 '13

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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 Feb 19 '13

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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answered Feb 18 '13

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

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]);
}

Comments

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

benzun (Feb 19 '13)edit

Does not matter.It is also true method.

Mostafa Sataki (Feb 19 '13)edit

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answered Feb 18 '13

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

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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Return RGB values of the the current Pixel ?

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Return RGB values of the the current Pixel ?