update samples: waitKey() usage

Original commit is a5f19f7dd6ae5bc93f73e0417a9e0bfd34c01672

samples/cpp/tutorial_code/ImgProc/Pyramids.cpp

@@ -45,26 +45,22 @@ int main( void )
   //![infinite_loop]
   for(;;)
   {
-    int c;
-    c = waitKey(0);
+    char c = (char)waitKey(0);
 
-    if( (char)c == 27 )
+    if( c == 27 )
       { break; }
-    if( (char)c == 'u' )
-      {
-        //![pyrup]
-        pyrUp( tmp, dst, Size( tmp.cols*2, tmp.rows*2 ) );
-        //![pyrup]
+    //![pyrup]
+    if( c == 'u' )
+      { pyrUp( tmp, dst, Size( tmp.cols*2, tmp.rows*2 ) );
         printf( "** Zoom In: Image x 2 \n" );
       }
-    else if( (char)c == 'd' )
-      {
-        //![pyrdown]
-        pyrDown( tmp, dst, Size( tmp.cols/2, tmp.rows/2 ) );
-        //![pyrdown]
+    //![pyrup]
+    //![pyrdown]
+    else if( c == 'd' )
+      { pyrDown( tmp, dst, Size( tmp.cols/2, tmp.rows/2 ) );
         printf( "** Zoom Out: Image / 2 \n" );
       }
-
+    //![pyrdown]
     imshow( window_name, dst );
 
     //![update_tmp]

samples/cpp/tutorial_code/ImgProc/Threshold.cpp

@@ -60,9 +60,8 @@ int main( int, char** argv )
   /// Wait until user finishes program
   for(;;)
     {
-      int c;
-      c = waitKey( 20 );
-      if( (char)c == 27 )
+      char c = (char)waitKey( 20 );
+      if( c == 27 )
     { break; }
     }
 

samples/cpp/tutorial_code/ImgProc/Threshold_inRange.cpp

@@ -41,7 +41,7 @@ int main()
     createTrackbar("Low B","Object Detection", &low_b, 255, on_low_b_thresh_trackbar);
     createTrackbar("High B","Object Detection", &high_b, 255, on_high_b_thresh_trackbar);
     //! [trackbar]
-    while(char(waitKey(1))!='q'){
+    while((char)waitKey(1)!='q'){
         //! [while]
         cap>>frame;
         if(frame.empty())