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//call DrawIcon passing the x and y coordinates g.DrawIcon(i, 150, 15);

//draw a Rectangle

Pen p2;

p2 = new Pen(Color.PapayaWhip, 7);

/* draw the Rectangle passing the x, y, * height and width */

g.DrawRectangle(p2, 50, 50, 100, 100);

}

If you call this method from a Windows Forms application, your results will look something like what is shown in Figure 26-1.

Alone, the Graphics class does nothing. To create lines, rectangles, images, and fonts, you use other objects along with the Graphics object. Listing 26-1 created a Pen object to use in conjunction with the Graphics object to draw a red line on the form. It also created an Icon object, which the Graphics object used to draw the desktop icon on the form. As mentioned earlier, you can perform numerous tasks with GDI+; draw shapes and lines, manipulate images, and work with fonts. The following sections delve more deeply into these topics, describing how you can use objects such as the Pen, Brush, and Image in conjunction with members of the Graphics class to take full advantage of the vast array of GDI+ capabilities in

.NET.

Working with Images in GDI+

If you need to render images that exist in the file system, the Image class gives you the capability to render images on surfaces created with the Graphics object. Contained in the System.Drawing namespace, the Image class is an abstract class that provides you with all of the functionality you need to use bitmaps, icons, and metafiles with a Graphics object to render predefined Image objects on a form. The rendered images can come directly from the file system, or they can come from a memory stream; either way, you are still dealing with some sort of image source. Images can be of type JPG, ICO, or BMP.

In Listing 26-2, you load a JPG file from the local drive to display on a form. This example is slightly different from what you have done earlier. Here, you are going to override the OnPaint event of the form so that the image will not be destroyed if another window happens to sit on top of your window. This example also shows you how to implement calling Dispose method in the Graphics object that is used to paint the JPG image when the form is destroyed.

Listing 26-2: Using Images with GDI+

namespace RenderJPG

{

public class Form1 : System.Windows.Forms.Form

{

private System.ComponentModel.Container components = null;

// declare image variable private Image img;

public Form1()

{

InitializeComponent();

// load the image

img = new Bitmap(@"C:\money.jpg");

//

}

protected override void Dispose( bool disposing )

{

if( disposing )

{

// Call DISPOSE on the Img object img.Dispose();

//

if (components != null)

{

components.Dispose();

}

}

base.Dispose( disposing );

}

static void Main()

{

Application.Run(new Form1());

}

// override the OnPaint event

protected override void OnPaint(PaintEventArgs p)

{

Graphics g = p.Graphics; g.DrawImage(img, 0,0);

}

}

}

Running this application should produce output similar to that shown in Figure 26-2.

Figure 26-2: Output from Listing 26-2 using a JPG with GDI+

The DrawImage method used to paint the image on the form has about 20 overloaded constructors. Basically, each one directs the method how to paint the image, such as coordinates or height and width. By making a simple change to the DrawImage method, you can fill the entire form with the bitmap. If you pass the constant ClientRectangle to DrawImage, as the next snippet demonstrates, your output will look like Figure 26-3, with the entire bitmap filling the screen:

Figure 26-3: Image filling the entire form

// override the OnPaint event

protected override void OnPaint(PaintEventArgs p)

{

Graphics g = p.Graphics; g.DrawImage(img, ClientRectangle);

}

You can also return properties on an image without displaying it. In the following Load event, you examine several of the available properties of the money.jpg image that you loaded earlier:

private void Form1_Load(object sender, System.EventArgs e)

{

MessageBox.Show (img.PhysicalDimension.ToString() );

MessageBox.Show (img.Height.ToString() );

MessageBox.Show (img.Width.ToString() );

MessageBox.Show (img.RawFormat.ToString() );

MessageBox.Show (img.Size.ToString() );

}

Table 26-3 describes each of the properties that are available for images through the Image class.

You can also use several methods in the Image class, which enable you to manipulate your images in virtually unlimited ways. The following code flips the image 90 degrees:

img.RotateFlip(RotateFlipType.Rotate90FlipY);

The RotateFlipType enumeration enables you to specify how you want to flip or rotate an image on the graphics surface.

Table 26-4 lists the remaining methods in the Image class that you can use to manipulate an image.

protected override void OnPaint(PaintEventArgs e)

{

Graphics g = e.Graphics;

SolidBrush sb = new SolidBrush(Color.Black); g.FillEllipse(sb, ClientRectangle);

}

Running the preceding code produces an image like the one shown in Figure 26-6.

Figure 26-6: A solid ellipse using a brush

The types of brush that you can create come in several flavors. A SolidBrush, which was used in the preceding example, fills a shape with a solid color. Using a HatchBrush enables you to get a little crazy with the way your graphics appear. The HatchBrush uses the HatchStyle enumeration and the HatchFill enumeration to display different pattern types. Listing 26-4 prints several of the HatchBrush variations using the HatchStyle enumeration. The HatchStyle enumeration has over 40 members, so it is worth looking up in the .NET Framework SDK. If you ever need to do any type of pattern drawing, you can find substantial support.

Listing 26-4: Using the HatchBrush Class with HatchStyles

protected override void OnPaint(PaintEventArgs e)

{

Graphics g = e.Graphics;

HatchBrush hb =

new HatchBrush (HatchStyle.Plaid, Color.AntiqueWhite ,Color.Black);

g.FillEllipse(hb,30, 30, Width-50, 30);

HatchBrush hb2 = new HatchBrush (HatchStyle.LargeCheckerBoard, Color.AntiqueWhite ,Color.Black);

g.FillEllipse(hb2, 30, 80, Width-50, 30);

HatchBrush hb3 =

new HatchBrush

method from the Graphics object that will hold the brush. Listing 26-5 prints the phrase C# is cool onto the current form and outputs something similar to what is shown in Figure 26-8.

Figure 26-8: Using the DrawString method and the Font class to output text Listing 26-5: Using the DrawString Method

protected override void OnPaint(PaintEventArgs e)

{

Graphics g = e.Graphics; e.Graphics.FillRectangle(

new SolidBrush(Color.White), ClientRectangle);

g.DrawString("C# is cool", this.Font,

new SolidBrush(Color.Black), 15, 15);

}

Note In .NET, fonts used on a Form object are inherited from the form itself. In this example, the font property in the form is set to 24, so when the this.Font value is passed to the DrawString method, it uses the current font size of the form.

Table 26-7 lists the available properties of the Font class. By setting or retrieving these properties on Font objects that you create, you can completely control the output of the text on the screen.