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This chapter is from the book

Filling Shapes

So far, we've dealt with the outline of a shape. Now we will focus on the interior, or fill area, of a shape. GDI+ gives us the concept of a brush to indicate how a shape is filled. Brushes are useful when blending colors for a desired effect like a fade or indicating a shape's texture like sand, stone, or brick. Brushes can be a single solid color, a blend of colors, a texture, a bitmap, or a hatched pattern.

To create brush objects in our code, we use a derivative of the Brush class. Brush is an abstract base class. Classes that derive from Brush are as follows: SolidBrush, TextureBrush, RectangleGradientBrush, LinearGradientBrush, and HatchBrush. This section discusses the various Brush derivatives.

SolidBrush

The SolidBrush class could not be more basic. It works just as it sounds; it provides a single-colored brush with which to fill shapes. It has one constructor and one property, Color. Of course, this property is of the type Color structure. The following is an example of how to create a SolidBrush object:

Dim myBrush as New SolidBrush(color:=Color.Red)

TextureBrush

To create custom fill effects, you use the TextureBrush class. Custom fills are useful when you want to apply your own design to the interior of a shape. For example, suppose you've created a bar graph and you want to fill each bar with the logo of a different company. The TextureBrush class would allow you to use a bitmap of each company's logo to fill each rectangle or bar in the graph. Using the TextureBrush class and bitmap images, you can create endless fill patterns.

The following code creates a TextureBrush instance based on a simple bitmap made up of three 45° lines. The bitmap is defined inside of an ImageList control (imageList1). When we create the object instance, we set the WrapMode parameter to the TileFlipXY enumeration member. This reverses the image both vertically and horizontally before it is applied to the graphic surface.

'dimension a local variable of type TextureBrush Class
Dim myBrush As TextureBrush

'create a new instance of TextureBrush 
myBrush = New TextureBrush(imageList1().Images.Item(0), _
	Drawing.Drawing2D.WrapMode.TileFlipXY)

Table 9.6 demonstrates how you can use the WrapMode property to tile an image inside the TextureBrush object to create a desired effect.

Table 9.6 TextureBrush WrapMode Enumeration

Effect

Description

This is the original 16 x 16 bitmap that is used to create the various effects.

A 32 x 32 filled area using the WrapMode.Tile property. The 16 x 16 bitmap is repeated four times in a tiled fashion.

A 32 x 32 filled area using the WrapMode.TileFlipX property. The 16 x 16 bitmap is reversed horizontally and then repeated four times (tiled).

A 32 x 32 filled area using the WrapMode.TileFlipY property. The 16 x 16 bitmap is reversed vertically and then repeated four times (tiled).

A 32 x 32 filled area using the WrapMode.TileFlipXY property. The 16 x 16 bitmap is reversed vertically and horizontally before being tiled.


LinearGradientBrush

In Windows 9x and above, you've undoubtedly seen how you can blend two colors across the title bar of a window from within the "Display Settings" control panel. Well, the LinearGradientBrush class allows us to do just that; we can blend two colors across a given shape.

To do so, we first create an instance of the class based on two colors and a blend style. Blend styles are defined by the LinearGradientMode enumeration. We then use a fill method of the Graphics object to paint our shape with the blended style. Listing 9.4 illustrates this by creating a Rectangle object and then using the blended LinearGradientBrush to fill its interior by calling FillRectangle.

Listing 9.4 LinearGradientBrush

Private Sub Button1_Click(ByVal sender As System.Object, _
  ByVal e As System.EventArgs) Handles Button1.Click

  'local scope
  Dim myGraphics As Graphics
  Dim myBrush As System.Drawing.Drawing2D.LinearGradientBrush
  Dim myRectangle As Rectangle

  'return the current form as a drawing surface
  myGraphics = Graphics.FromHwnd(hwnd:=ActiveForm().Handle)

  'create a rectangle object
  myRectangle = New Rectangle(x:=5, y:=5, Width:=40, Height:=50)

  'draw the rectangle to the surface
  myGraphics.DrawRectangle(pen:=New Pen(Color.Black), rect:=myRectangle)

  'create the gradient brush
  myBrush = New System.Drawing.Drawing2D.LinearGradientBrush( _
   rect:=myRectangle, _
   color1:=Color.White, _
   color2:=Color.DarkSlateBlue, _
   LinearGradientMode:= _
   System.Drawing.Drawing2D.LinearGradientMode.Vertical)

  'fill the rectangle using the gradient brush
  myGraphics.FillRectangle(brush:=myBrush, rect:=myRectangle)

End Sub

Notice that when we created the brush, we set the LinearGradientMode parameter to indicate a blend from the top of the shape to its bottom (Vertical). You can get the four effects defined in Table 9.7 by using this enumeration.

Table 9.7 LinearGradientMode Enumeration

Member

Effect

Description

Vertical

The Vertical member indicates a fill pattern from the top of the object to the bottom.

Horizontal

The Horizontal member indicates a fill pattern from the left of an object to its right.

ForwardDiagonal

The ForwardDiagonal member indicates a fill pattern from the upper-left corner of an object to the lower-right corner.

BackwardDiagonal

The BackwardDiagonal member indicates a fill pattern from the upper-right corner of an object to the lower-left corner.


HatchBrush

Remember the first paint programs? Remember showing your friends a wall built out of red brick that you drew with a rectangle and filled with the brick pattern? Well, the HatchBrush class allows us to create numerous predefined fill patterns, including brick.

We create a HatchBrush by passing in a hatch style, using the HatchStyle enumeration, and a foreground and background color to be used by the hatch style. Listing 9.5 fills an ellipse using a checkerboard HatchBrush instance.

Listing 9.5 HatchBrush

Private Sub Button1_Click(ByVal sender As System.Object, _
  ByVal e As System.EventArgs) Handles Button1.Click

  'local scope
  Dim myGraphics As Graphics
  Dim myBrush As System.Drawing.Drawing2D.HatchBrush
  Dim myRectangle As Rectangle

  'return the current form as a drawing surface
  myGraphics = Graphics.FromHwnd(hwnd:=ActiveForm().Handle)

  'create a rectangle object to bind the ellipse
  myRectangle = New Rectangle(x:=5, y:=5, Width:=70, Height:=60)

  'draw the ellipse to the surface
  myGraphics.DrawEllipse(pen:=New Pen(Color.Black), rect:=myRectangle)

  'create the hatch brush
  myBrush = New System.Drawing.Drawing2D.HatchBrush( _
    hatchstyle:=Drawing.Drawing2D.HatchStyle.LargeCheckerBoard, _
    ForeColor:=Color.Black, _
    BackColor:=Color.White)

  'fill the ellipse using the hatch brush
  myGraphics.FillEllipse(brush:=myBrush, rect:=myRectangle)

End Sub

Table 9.8 provides a visual representation of the various patterns possible using the HatchBrush class. Hopefully, this will serve as a handy reference when you need to pick the perfect pattern. A description of each member is not necessary; the associated graphic tells the whole story. Remember, the table uses black and white, but you can use any color for the foreColor and backColor parameters for nearly unlimited effects.

Table 9.8 HatchStyle Enumeration

Member

Effect

Member

Effect

Horizontal

Vertical

LightHorizontal

LightVertical

DarkHorizontal

DarkVertical

DashedHorizontal

DashedVertical

NarrowHorizontal

NarrowVertical

DiagonalBrick

Cross

HorizontalBrick

DiagonalCross

SmallGrid

SolidDiamond

LargeGrid

DottedDiamond

DottedGrid

OutlinedDiamond

SmallCheckerBoard

SmallConfetti

LargeCheckerBoard

LargeConfetti

Percent05

Percent10

Percent20

Percent25

Percent30

Percent40

Percent50

Percent60

Percent70

Percent75

Percent80

Percent90

Plaid

Sphere

Trellis

Shingle

Wave

Weave

BackwardDiagonal

ForwardDiagonal

DarkDownwardDiagonal

LightDownwardDiagonal

DarkUpwardDiagonal

LightUpwardDiagonal

DashedDownwardDiagonal

DashedUpwardDiagonal

WideDownwardDiagonal

WideUpwardDiagonal

Divot

 

 


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