[HighGUI] On Windows: Support Ctrl+C to copy image to clipboard.

modules/highgui/src/window_w32.cpp

@@ -1286,6 +1286,10 @@ MainWindowProc( HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam )
 
     switch(uMsg)
     {
+    case WM_COPY:
+      ::WindowProc(hwnd, uMsg, wParam, lParam); // call highgui proc. There may be a better way to do this.
+      break;
+
     case WM_DESTROY:
 
         icvRemoveWindow(window);
@@ -1448,6 +1452,81 @@ static LRESULT CALLBACK HighGUIProc( HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM
     // Process the message
     switch(uMsg)
     {
+    case WM_COPY:
+        {
+            if (!::OpenClipboard(hwnd) )
+                break;
+
+            HDC hDC       = 0;
+            HDC memDC     = 0;
+            HBITMAP memBM = 0;
+
+            // We'll use a do-while(0){} scope as a single-run breakable scope
+            // Upon any error we can jump out of the single-time while scope to clean up the resources.
+            do
+            {
+               if (!::EmptyClipboard())
+                  break;
+
+               if(!window->image)
+                  break;
+
+               // Get window device context
+               if (0 == (hDC = ::GetDC(hwnd)))
+                  break;
+
+               // Create another DC compatible with hDC
+               if (0 == (memDC = ::CreateCompatibleDC( hDC )))
+                  break;
+
+               // Determine the bitmap's dimensions
+               int nchannels = 3;
+               SIZE size = {0,0};
+               icvGetBitmapData( window, &size, &nchannels, 0 );
+
+               // Create bitmap to draw on and it in the new DC
+               if (0 == (memBM = ::CreateCompatibleBitmap ( hDC, size.cx, size.cy)))
+                  break;
+
+               if (!::SelectObject( memDC, memBM ))
+                  break;
+
+               // Begin drawing to DC
+               if (!::SetStretchBltMode(memDC, COLORONCOLOR))
+                  break;
+
+               RGBQUAD table[256];
+               if( 1 == nchannels )
+               {
+                  for(int i = 0; i < 256; ++i)
+                  {
+                     table[i].rgbBlue = (unsigned char)i;
+                     table[i].rgbGreen = (unsigned char)i;
+                     table[i].rgbRed = (unsigned char)i;
+                  }
+                  if (!::SetDIBColorTable(window->dc, 0, 255, table))
+                     break;
+               }
+
+               // The image copied to the clipboard will be in its original size, regardless if the window itself was resized.
+
+               // Render the image to the dc/bitmap (at original size).
+               if (!::BitBlt( memDC, 0, 0, size.cx, size.cy, window->dc, 0, 0, SRCCOPY ))
+                  break;
+
+               // Finally, set bitmap to clipboard
+               ::SetClipboardData(CF_BITMAP, memBM);
+            } while (0,0); // (0,0) instead of (0) to avoid MSVC compiler warning C4127: "conditional expression is constant"
+
+            //////////////////////////////////////////////////////////////////////////
+            // if handle is allocated (i.e. != 0) then clean-up.
+            memBM && ::DeleteObject(memBM);
+            memDC && ::DeleteDC(memDC);
+            hDC   && ::ReleaseDC(hwnd, hDC);
+            ::CloseClipboard();
+            break;
+        }
+
     case WM_WINDOWPOSCHANGING:
         {
             LPWINDOWPOS pos = (LPWINDOWPOS)lParam;
@@ -1798,6 +1877,11 @@ cvWaitKey( int delay )
                         is_processed = 1;
                         return (int)(message.wParam << 16);
                     }
+
+                    // Intercept Ctrl+C for copy to clipboard
+                    if ('C' == message.wParam && (::GetKeyState(VK_CONTROL)>>15))
+                        ::PostMessage(message.hwnd, WM_COPY, 0, 0);
+
                 default:
                     DispatchMessage(&message);
                     is_processed = 1;