CHA PTE R 8 in C#.NET

Drawer Data Matrix 2d barcode in C#.NET CHA PTE R 8

UPDATING THE PIXELDLG FORM So far we have created and displayed our form as a modeless dialog. In this section we will implement the code to update this dialog based on the current location of the mouse pointer in the pnlPhoto control. We will account for the fact that a photo might not be displayed, and that the mouse pointer may be located outside of the panel. This code for UpdatePixelData is a bit long, so let s get to it.

IMPLEMENT UPDATEPIXELDATA METHOD Action 1 In the MainForm.cs window, add an UpdatePixelData method to the end of the file. Return immediately if the

protected void UpdatePixelData (int xPos, int yPos) { if (_dlgPixel == null || !_dlgPixel.Visible) return;

visible. 3 4 Get the currently display photo. Display all zeros if a Photograph is not displayed or the given coordinates are outside the display area. Note: The question mark syntax here works the same as in C++.

Photograph photo = _album.CurrentPhoto; Rectangle r = pnlPhoto.ClientRectangle; if (photo == null || !(r.Contains(xPos,yPos))) { _dlgPixel.Text = ((photo == null) " " : photo.Caption); _dlgPixel.XVal = 0; _dlgPixel.YVal = 0; _dlgPixel.RedVal = 0; _dlgPixel.GreenVal = 0; _dlgPixel.BlueVal = 0; _dlgPixel.Update(); return; } _dlgPixel.Text = photo.Caption;

Display the caption for the current image in the title bar of our dialog. Use a switch statement to determine the current display mode. Note: The calculation here depends on how the image is displayed, so a switch statement is required.

// Calc x and y position in the photo int x = 0, y = 0; Bitmap bmp = photo.Image; switch (this._selectedMode) {

Implement the Actual Size display mode logic. Note: In this mode, the display area and image area are equivalent.

case DisplayMode.ActualSize: // Panel coords equal image coords x = xPos; y = yPos; break;

IMPLEMENT UPDATEPIXELDATA METHOD (continued) Action 8 Implement the Stretch to Fit display mode logic. Note: In this mode, the image fills the entire display area, so we convert from display position to image location. 9 Implement the Scale to Fit display mode logic.

case DisplayMode.StretchToFit: // Translate panel coords to image x = xPos * bmp.Width / r.Width; y = yPos * bmp.Height / r.Height; break;

case DisplayMode.ScaleToFit: // Determine image rectangle. Rectangle r2 = photo.ScaleToFit(r); if (!r2.Contains(xPos, yPos)) return; // Mouse outside image // Translate r2 coords to image x = (xPos - r2.Left) * bmp.Width / r2.Width; y = (yPos - r2.Top) * bmp.Height / r2.Height; break; }

a. Calculate the rectangle containing the image using the ScaleToFit method in the Photograph class. b. If the mouse pointer is outside this rectangle, it is not in the image. c. Otherwise, convert this rectangle into image coordinates. 10 Retrieve the color of the pixel at the calculated image location.

// Extract color at calculated location Color c = bmp.GetPixel(x, y);

// Update PixelDlg with new values _dlgPixel.XVal = x; _dlgPixel.YVal = y; _dlgPixel.RedVal = c.R; _dlgPixel.GreenVal = c.G; _dlgPixel.BlueVal = c.B; _dlgPixel.Update(); }

And there you have it. This method updates the PixelDlg form each time it is called. Since the explanation of each step is embedded in the table, we will not discuss this code further. Our final task is to make sure this method is called each time the mouse pointer moves or the displayed photograph changes. 8.4.5 UPDATING PIXELDLG AS THE MOUSE MOVES In the previous section we waded through the logic necessary to convert the current mouse pointer location in panel coordinates to the corresponding image coordinates to update the PixelDlg form correctly. Next, we need to ensure that UpdatePixelData is called whenever appropriate.

The most obvious time is whenever the location of the mouse pointer changes. There is a MouseMove event inherited from the Control class for this purpose. The protected OnMouseMove method raises this event, so we could override OnMouseMove in our Form class. In this case, we would have to convert from Form coordinates to Panel coordinates, so handling the event for the Panel class is probably a better choice. More importantly, by handling mouse pointer movements in the Panel object directly, our code is only called when the movement occurs inside the panel.

CALL THE UPDATEPIXELDATA METHOD WHEN THE MOUSE MOVES ACTION 1 In the MainForm.cs [Design] window, add a MouseMove event handler for the pnlPhoto object. Call the UpdatePixelData method with the current mouse pointer coordinates. RESULT

protected void pnlPhoto_MouseMove (object sender, System.Windows.Forms.MouseEventArgs e) { UpdatePixelData(e.X, e.Y); }

The MouseMove event handler receives a MouseEventArgs parameter containing, among other event data, an X and Y property defining the current coordinates of the mouse pointer in the control s coordinates. We will discuss this and other mouse events in chapter 12, so we will not go into more detail on this handler here. The one other instance when the pixel values must be updated is when the displayed image changes. The easiest place to track this is when the Panel is painted in the pnlPhoto_Paint method. Continuing the previous steps:

CALL UPDATEPIXELDATA WHEN CURRENT PHOTO CHANGES Action 3 Locate the pnlPhoto_Paint method in the MainForm.cs source file. Call UpdatePixelData if a new photo is displayed. Result

protected void pnlPhoto_Paint(. . .) {

// Update PixelDlg if photo has changed if ((_dlgPixel != null) && (_nPixelDlgIndex != _album.CurrentPosition)) { _nPixelDlgIndex = _album.CurrentPosition; Point p = pnlPhoto.PointToClient( Form.MousePosition); UpdatePixelData(p.X, p.Y); } // Paint the current photo, if any if (_album.Count > 0) { . . . } }