10.2.5.6   Graphics Windows

HALCON provides a functionality that emulates the behavior of HDevelop graphics windows for HALCON windows. This HALCON window stack is accessible via class methods and functions in the HALCON interfaces, and code exported from HDevelop uses this functionality when opening, closing, setting, or accessing the active window. The HALCON window stack mechanism is threadsafe and can be shared among threads. Though, in a multithreaded application the user has to take care when switching the active window in different threads, as setting it in one thread will also set it for other threads.

For the .NET code export it is optional whether to export HDevelop programs as code using the HDevelop export example templates or as code using the previously described HALCON window stack functionality when doing graphics windows output. Additionally, in the latter case the exported code contains a main function and thus is usable as a standalone application. The HDevelop Export dialog allows you to select the corresponding option.

The graphics windows of HDevelop and the basic windows of the HALCON libraries

• HALCON/C++: class HWindow,
• HALCON/.NET: class HWindowControl, and
• HALCON/C: addressed via handles

have different functionality.

• Multiple windows    
  If you use the operator dev_open_window to open multiple graphics windows in HDevelop, these calls will be converted into corresponding calls of open_window only if the export option Use HALCON Windows is selected.

  In the export of Visual Basic .NET, and C# programs using the option Use Export Template, all window operations are suppressed, because the exported code is intended to work together with the corresponding template. If you want to use more than one window in programs exported in this mode, you have to modify the code and project manually.

  Note that the export of programs containing multiple windows using the option Use HALCON Windows might be incorrect if the active graphics window was changed using the mouse during program execution. It is recommended to use the operator dev_set_window explicitly to achieve the same functionality.

• Window size    
  In exported Visual Basic .NET, and C# programs, the size of the window on the form is predefined (512 × 512); thus, it will normally not fit your image size. Therefore, you must adapt the size interactively or by using the properties of the window.

• Displaying results    
  Normally, the result of every operator is displayed in the graphics window of HDevelop. This is not the case when using an exported program. It behaves like the HDevelop program running with the option: “update window = off”. We recommend inserting the operator dev_display in the HDevelop program at each point where you want to display data. This will not change the behavior of the HDevelop program but result in the appropriate call in the exported code.

  When generating code using the option Use HALCON Windows, close the default graphics window (using dev_close_window) and open a new one (using dev_open_window) before the first call of dev_display in order to assure a correct export.

• Displaying images    
  In HDevelop, images are automatically scaled to fit the current window size. This is not the case in exported programs. For example, if you load and display two images of different size, the second one will appear clipped if it is larger than the first image or filled up with black areas if it is smaller. For a correct display, you must use the operator dev_set_part before displaying an image with dev_display as follows:

    dev_set_part (0, 0, ImageHeight-1, ImageWidth-1)
    dev_display (Image)
  

  In this example, Image is the image variable, ImageHeight and ImageWidth denote its size. You can query the size of an image with the operator get_image_size. Please consult the HALCON Reference Manuals for more details.

  Note that the operator dev_set_part (and its HALCON library equivalent set_part) is more commonly used for displaying (and thereby zooming) parts of images. By calling it with the full size of an image as shown above, you assure that the image exactly fits the window.

• Changing display parameters    
  If you change the way how results are displayed (color, line width, etc.) in HDevelop interactively via the menu Visualization, these changes will not be incorporated in the exported program. We recommend inserting the corresponding Develop operators (for example, dev_set_color or dev_set_line_width) in the HDevelop program explicitly. This will result in the appropriate call (set_color, set_line_width, etc.) in the exported code.