[Solved]Threshold on partial of image

[soheil1365]

Hi guys..
I am doing a project with opencv and Qt...
I have a image which is displayed on Qgraphicsview...Then I drew a rectangle by cv::rect on it...
@////////////////////////////////////////////////////////////////////////////////////////////////
CvRect rectn;
rectn.x=ui->txtxn1->toPlainText().toInt();
rectn.y=ui->txtyn1->toPlainText().toInt();
rectn.height=ui->txtheightBlack->toPlainText().toInt();
rectn.width=ui->txtwidthBlack->toPlainText().toInt();
cv::rectangle(img,rectn,COLOR_RGB2RGBA,1,8,0);
/////////////////////////////////////////////////////////////////////////////////////////////////@
This rectangle is drawn on my image which is loaded in Qgraphicsview.

Now I want to separate this rectangle from my image and do thresholding on it....
How can I do that?I do not want do thresholding on whole of the image just on this rectangle...

please help me...
thanks in advance...

[DerManu]

You have the full rect information in rectn (x, y, width, height), so just loop over that rect with QImage::scanLine and do the thresholding.