使用Opencv和Qt对两个灰度图像的使用条款相减

Question

I want to subtract two Images in gray-scale every 40ms, I capture two Images every 40ms from two cameras then set the two Images size to( height =480, width =640), after that I convert to gray-scale. but when I use the subtraction (absdiff) for the two Images I get "Run-time Error". I noticed that when I display the size of the two Images I get a unmatched Results in the size of the two gray-scale Images.

src_gray1 cols is: =640 src_gray1 rows is: =480  src_gray1.size =0x28fd5c
src_gray2 cols is: =640  src_gray2 rows is: =480  src_gray2.size =0x28fdcc

in the Header I declared: cv::Mat edges1 , src_gray1 , edges2 , src_gray2 , src_gray3;

my question: whats the problem in subtraction method, is the size of the gray-scale Mat is the problem?, how I can set Same properties for the two images to get Over that.

I use Qt 5.5.0, my code here:

void MainWindow::on_pushButton_pressed()
{
     timer_40_ms->start();
     timer2_40_ms->start();
     cap1.open(0);
     if( !cap1.isOpened() )
     {
         std::cout<<"Camera1 did not open";
         return;
     }
     cap2.open(1);
     if( !cap2.isOpened() )
     {
         std::cout<<"Camera2 did not open";
         return;
     }
     cap1.set(CV_CAP_PROP_FRAME_HEIGHT,480);
     cap1.set(CV_CAP_PROP_FRAME_WIDTH,640);
     cap2.set(CV_CAP_PROP_FRAME_HEIGHT,480);
     cap2.set(CV_CAP_PROP_FRAME_WIDTH,640);

 }
 void MainWindow::ProcessFrame()
 {
     cv::Mat frame1;
     ii++;
     ui->textEdit->setText(QString::number(ii));
     cap1 >> frame1;
     cvtColor(frame1, src_gray1, CV_BGR2GRAY);
     std::cout<<"src_gray1 cols is:"<<" ="<<src_gray1.cols<<" "<<"src_gray1  rows is:"<<" ="<<src_gray1.rows<<"  "<<"src_gray1.size ="<<src_gray1.size<<'\n';
  }
void MainWindow::ProcessFrame2()
{
    cv::Mat frame2;
    ii2++;
    cap2 >> frame2;
    cvtColor(frame2, src_gray2, CV_BGR2GRAY);
    ui->textEdit_3->setText(QString::number(ii2));
    absdiff(src_gray1,src_gray2,src_gray3);
    cv::imshow( "CAM2 Video Labeler", src_gray3 );
    std::cout<<"src_gray2 cols is:"<<" ="<<src_gray2.cols<<"  "<<"src_gray2  rows is:"<<" ="<<src_gray2.rows<<"  "<<"src_gray2.size ="<<src_gray2.size<<'\n';
}

Answer 1

the problem was that ProcessFrame2() is invoked before ProcessFrame(), thank you @dan Masek for help:

     void MainWindow::on_pushButton_pressed()
   {
     timer_40_ms->start();
     timer2_40_ms->start();
     cap1.open(0);
     if( !cap1.isOpened() )
     {
         std::cout<<"Camera1 did not open";
         return;
     }
     cap2.open(1);
     if( !cap2.isOpened() )
     {
         std::cout<<"Camera2 did not open";
         return;
     }
     cap1.set(CV_CAP_PROP_FRAME_HEIGHT,480);
     cap1.set(CV_CAP_PROP_FRAME_WIDTH,640);
     cap2.set(CV_CAP_PROP_FRAME_HEIGHT,480);
     cap2.set(CV_CAP_PROP_FRAME_WIDTH,640);

   }
 void MainWindow::ProcessFrame()
 {
     cv::Mat frame1;
     ii++;
     ui->textEdit->setText(QString::number(ii));
    cap1 >> frame1;
    cvtColor(frame1, src_gray1, CV_BGR2GRAY);
    absdiff(src_gray1,src_gray2,src_gray3);
    cv::imshow( "CAM2 Video Labeler", src_gray3 );
    std::cout<<"src_gray1 cols is:"<<" ="<<src_gray1.cols<<" "<<"src_gray1  rows is:"<<" ="<<src_gray1.rows<<"  "<<"src_gray1.size ="<<src_gray1.size<<'\n';
  }
void MainWindow::ProcessFrame2()
{
    cv::Mat frame2;
    ii2++;
    cap2 >> frame2;
    cvtColor(frame2, src_gray2, CV_BGR2GRAY);
    ui->textEdit_3->setText(QString::number(ii2));

   std::cout<<"src_gray2 cols is:"<<" ="<<src_gray2.cols<<"  "<<"src_gray2  rows is:"<<" ="<<src_gray2.rows<<"  "<<"src_gray2.size ="<<src_gray2.size<<'\n';
   }