This article has been
excerpted from book "Graphics Programming with GDI+".
In this section we will extend the functionality of GDI+Painter by adding
support for brushes and pens. After completing this section, you will be able to
select a pen color and its width, color transparency, and brush color.
Figure 4.32 shows the modified version of GDI+Painter without any objects.
Transparency is a component of the color in GDI+. In the .NET Framework library;
the Color structure represents a color. It has four components: alpha (A), red(R),
green (G), and blue (B). The alpha component of the Color structure represents
the transparency of a color. The alpha component values vary from 0 to 255,
where 0 is fully transparent and 255 is fully opaque. Tocreate a transparent
brush or pen, we create a color using the alpha value and use the color to
create a pen or a brush.
FIGURE 4.32: GDI+ Painter with pen and brush support
The following code snippet shows how to create a color with transparency. We use
the same method to add transparency to our application.
Color clr =
Color.FromArgb(Convert.ToInt16
(TransCounter.Value.ToString()), PenBtn.BackColor.R, PenBtn.BackColor.G,
PenBtn.BackColor.B);
In our modified version of GDI+Painter, the width selector numeric up-down
control allows you to select the width of the pen. A pen is used when we draw
the outlines of graphics shapes. A brush is used when we draw filled graphics
shapes.
The Pen color and Brush color buttons launch ColorDialog, which lets us select a
color and set the color of the button itself, which later is used by the program
when creating a Pen or Brush object. Listing 4.27 shows the code for these two
button click event handlers. This code also sets the background color of the
respective buttons to set the current selected color of our brush and pen.
LISTING 4.27: Selecting pen and brush colors
private void
PenSetting_click(object sender, System.EventArgs
e)
{
ColorDialog colorDlg =
new ColorDialog();
colorDlg.ShowDialog();
PenBtn.BackColor = colorDlg.Color;
}
private void
BrushSettings_click(object sender, System.EventArgs
e)
{
ColorDialog colorDlg =
new ColorDialog();
colorDlg.ShowDialog();
BrushBtn.BackColor = colorDlg.Color;
}
When we draw a graphics shape, we set the color, width and transparency of the
pen and brush according to the selection. The last two changes in our revised
version of GDI+Painter are on the mouse-up event handler and form's paint event
handler, respectively.
The modified mouse-up event handler is shown in listing 4.28.In it; we use the
color buttons to create our current pen and brush from the selected colors.
LISTING 4.28: The mouse-up event handler
private void
Form1_MouseUp(object sender,
System.Windows.Forms.MouseEventArgs e)
{
//Set the pen's color
curPen.Color = Color.FromArgb(Convert.ToInt16(TransCounter.Value.ToString()),
PenBtn.BackColor.R, PenBtn.BackColor.G, PenBtn.Color.B);
//Set the pen's width
curPen.Width = (float)PenWidthCounter.Value;
//Set the brush's color
curBrush.Color = Color.FromArgb(Convert.ToInt16(TransCounter.Value.ToString()),
BrushBtn.BackColor.R, BrushBtn.BackColor.G, BrushBtn.BackColor.B);
diffX = x - curX;
diffY = y - curY;
switch (drawIndex)
{
case 1:
{
//Draw a line
curGraphics.DrawLine(curPen, curX, CurY, x, y);
break;
}
case 2:
{
//Draw an ellipse
curGraphics.DrawEllipse(curPen, curX, curY, diffX,
diffY);
break;
xuan truong nguyenPosted May 24, 2011, 8:32 AM
i need code projec "The GDI+Painter Application" help me
jamil chPosted Nov 17, 2010, 3:09 AM
Mr.Puran Mehra I like your idea of Painter Application, can you provide the source code of this application or you can email it to me [email protected]. Thanks Jamil