Texture and Gradient Brushes

Texture Brushes

Introduction

The hatch brushes we have used are based on already designed patterns to fill a shape. In some cases, you may want to create or design your own pattern and use it to fill an area. To do this, you must perform two main steps. First, you must design a picture and save it as a file. Then you must create an object referred to as a texture brush and pass the picture to it.

A texture brush is an object that holds a picture and uses it to regularly fill the interior of a closed shape. To initialize it, you can use an existing picture designed by someone else or you can design your own picture using any normal graphics application, including Microsoft Paint that is automatically installed with Microsoft Window. You should have the picture as a file with a normal graphics file extension, which could be .bmp. Here is an example of a designed bitmap saved as Papers.bmp:

Equipped with the picture, you can then use the TextureBrush class that provides various constructors.

The simplest constructor of this class takes as argument an Image object. The syntax of this constructor is:

Public Sub New(bitmap As Image)

This constructor expects a bitmap as argument. After initializing the brush, you can use it to fill the interior of a closed shape. For example, you can call a Fill... method to paint its shape. Here is an example:

Imports System.Drawing
Imports System.Windows.Forms

Module Exercise

    Public Class Starter
        Inherits Form

        Dim components As System.ComponentModel.Container

        Public Sub New()
            InitializeComponent()
        End Sub

        Public Sub InitializeComponent()

        End Sub

        Private Sub FormPaint(ByVal sender As Object, _
                              ByVal e As PaintEventArgs) _
                              Handles MyBase.Paint

            Dim BmpPapers As Bitmap = New Bitmap("Papers.bmp")
            Dim BrushPapers As TextureBrush = New TextureBrush(BmpPapers)
            e.Graphics.FillRectangle(BrushPapers, 5, 5, 430, 280)


        End Sub
    End Class

    Function Main() As Integer

        Dim frmStart As Starter = New Starter

        Application.Run(frmStart)

        Return 0
    End Function

End Module

If you use this constructor, the compiler would itself find out the location and dimensions of the picture in the area where it was designed. Although the location must be at (0, 0), the width and the height must be lower or equal to the intended dimensions of the bitmap. For example, if you have a picture that is 48x48 pixels, the width you can use from this picture must be <= 48 and the height must be <= 48. This allows you to use only a portion of the picture if you want. To use a portion of the picture, you can use the following constructor:

Public Sub New(image As Image, dstRect As Rectangle)

The second argument to this constructor is used to specify the width and height of the picture. If you prefer to use a rectangle whose arguments are decimal numbers, you can use the following constructor:

Public Sub New(image As Image, dstRect As RectangleF)

Here is an example:

Private Sub FormPaint(ByVal sender As Object, _
                              ByVal e As PaintEventArgs) _
                              Handles MyBase.Paint

    Dim BmpPapers As Bitmap = New Bitmap("Papers.bmp")
    Dim BrushPapers As TextureBrush = New TextureBrush(BmpPapers, _
                                      New Rectangle(0, 0, 42, 42))
            e.Graphics.FillRectangle(brushPapers, 5, 5, 416, 290)

End Sub

The constructors we have used so far allow you to draw the bitmap in each allocated rectangle in a tiled fashion. To make it more fun, the TextureBrush class is equipped with a factor referred to as wrap mode. This factor specifies how the tiling must be performed. To apply it, you can use one of the following constructors:

Public Sub New(image As Image, wrapMode As WrapMode)
Public Sub New(image As Image, wrapMode As WrapMode, dstRect As Rectangle)
Public Sub New(image As Image, wrapMode As WrapMode, dstRect As RectangleF)

The bitmap and the destination arguments are used in the same way we have done so far. The wrapMode argument is a member of the WrapMode enumerator. The WrapMode enumerator is defined in the System.Drawing.Drawing2D namespace. It has the following members:

Clamp: Draws one picture in the allocated rectangle:

Imports System.Drawing
Imports System.Drawing.Drawing2D
Imports System.Windows.Forms

Module Exercise

    Public Class Starter
        Inherits Form

        Dim components As System.ComponentModel.Container

        Public Sub New()
            InitializeComponent()
        End Sub

        Public Sub InitializeComponent()

        End Sub

        Private Sub FormPaint(ByVal sender As Object, _
                              ByVal e As PaintEventArgs) _
                              Handles MyBase.Paint

            Dim bmpPapers As Bitmap = New Bitmap("Papers.bmp")
            Dim brushPapers As TextureBrush = New TextureBrush(bmpPapers, _
         			WrapMode.Clamp)
            e.Graphics.FillRectangle(brushPapers, 5, 5, 438, 290)

        End Sub
    End Class

    Function Main() As Integer

        Dim frmStart As Starter = New Starter

        Application.Run(frmStart)

        Return 0
    End Function

End Module

Tile: Draws the picture continuous in a tiled fashion:

Private Sub FormPaint(ByVal sender As Object, _
                              ByVal e As PaintEventArgs) _
                              Handles MyBase.Paint

            Dim BmpPapers As Bitmap = New Bitmap("Papers.bmp")
            Dim BrushPapers As TextureBrush = New TextureBrush(BmpPapers, _
                                                           WrapMode.Tile, _
                               New Rectangle(0, 0, 42, 42))
            e.Graphics.FillRectangle(BrushPapers, 5, 5, 414, 290)

End Sub

TileFlipX: Draws the picture, draws it again on its right side but flipped horizontally, and then repeats this technique continuous in a tiled fashion and in the allocated rectangle:

Private Sub FormPaint(ByVal sender As Object, _
                              ByVal e As PaintEventArgs) _
                              Handles MyBase.Paint

            Dim bmpPapers As Bitmap = New Bitmap("Papers.bmp")
            Dim brushPapers As TextureBrush = New TextureBrush(bmpPapers, _
                                                            WrapMode.TileFlipX)
            e.Graphics.FillRectangle(brushPapers, 5, 5, 430, 280)

End Sub

TileFlipY: Draws the picture, draws it again under it but flipped vertically, and then repeats this technique continuous in a tiled fashion and in the allocated rectangle:

Private Sub FormPaint(ByVal sender As Object, _
                              ByVal e As PaintEventArgs) _
                              Handles MyBase.Paint

            Dim bmpPapers As Bitmap = New Bitmap("Papers.bmp")
            Dim brushPapers As TextureBrush = New TextureBrush(bmpPapers, _
                                                           WrapMode.TileFlipX, _
                                                	New Rectangle(0, 0, 42, 42))
            e.Graphics.FillRectangle(brushPapers, 5, 5, 412, 290)

End Sub

TileFlipXY: Draws the picture, draws it again on its right side but flipped horizontally, then draws both the original and the right copy under each other but flipped vertically. These four pictures are redrawn in a tiled fashion and in the allocated rectangle:

Private Sub FormPaint(ByVal sender As Object, _
                              ByVal e As PaintEventArgs) _
                              Handles MyBase.Paint

            Dim bmpPapers As Bitmap = New Bitmap("Papers.bmp")
            Dim brushPapers As TextureBrush = New TextureBrush(bmpPapers, _
                                                       WrapMode.TileFlipXY, _
                                                    New Rectangle(0, 0, 42, 42))
            e.Graphics.FillRectangle(brushPapers, 5, 5, 412, 244)

End Sub

Practical Learning: Using Texture Brushes

1. Start a new Windows Forms Application named SchoolEnrolment2
2. Design the form as follows:
    

   Control Name Text Label   Enrolment / Program ___________________________ Label   Graduates Label   Undergraduates Label   Certificates TextBox txtGraduates 0 TextBox txtUndergraduates 0 TextBox txtCertificates 0 Button btnCreateChart Create Chart PictureBox pbxChart   Label   ____Legend____ Label lblGraduates Graduates Label lblUndergraduates Undergraduates Label lblCertificates Certificates Button btnClose Close

3. To design a bitmap, on the main menu, click Project -> Add New Item...
4. In the Templates list, click Bitmap File
5. Change the Name to graduates and click Add
6. To change the file location of the bitmap, on the main menu, click File -> Save graduates.bmp As...
7. Locate and display the SchoolEnrolment2\SchoolEnrolment2\bin\debug folder
8. Click Save
9. In the Solution Explorer, double-click graduates.bmp to make sure it is displayed
10. In the Properties Window, click Width and type 16
11. Click Height and type 16
12. Design the bitmap as follows:
     
    
13. In the Solution Explorer, right-click the Debug folder -> Add -> New Item...
14. In the Templates list, make sure Bitmap File is selected.
    Set the Name to undergraduates and click Add
15. In the Properties window, click Width and type 16
16. Click Height and type 16
17. Design the bitmap as follows:
     
    
18. In the Solution Explorer, right-click the Debug folder -> Add -> New Item...
19. In the Templates list, make sure Bitmap File is selected.
    Set the Name to certificates and click Add
20. In the Properties window, click Width and type 16
21. Click Height and type 16
22. Design the bitmap as follows:
     
    
23. Display the form
24. Right-click the form and click View Code
25. Declare three variables as follows:
     

    Public Class Form1 Dim Graduates As Single Dim Undergraduates As Single Dim Certificates As Single End Class

26. In the Class Name combo box, select (Form1 Events)
27. In the Method Name combo box, select Paint and implement the event as follows:
     

    Private Sub Form1_Paint(ByVal sender As Object, _ ByVal e As System.Windows.Forms.PaintEventArgs) _ Handles Me.Paint Dim bmpGraduates As Bitmap = New Bitmap("graduates.bmp") Dim BrushGraduates As TextureBrush = New TextureBrush(bmpGraduates) Dim bmpUndergraduates As Bitmap = New Bitmap("undergraduates.bmp") Dim brushUndergraduates As TextureBrush = _ New TextureBrush(bmpUndergraduates) Dim bmpCertificates As Bitmap = New Bitmap("certificates.bmp") Dim brushCertificates As TextureBrush = _ New TextureBrush(bmpCertificates) pbxChart.CreateGraphics().FillPie(BrushGraduates, _ 0.0F, 0.0F, _ 260.0F, 200.0F, 0.0F, Graduates) pbxChart.CreateGraphics().FillPie(brushUndergraduates, _ 0.0F, 0.0F, 260.0F, _ 200.0F, Graduates, Undergraduates) pbxChart.CreateGraphics().FillPie(brushCertificates, _ 0.0F, 0.0F, 260.0F, _ 200.0F, Graduates + Undergraduates, _ Certificates) e.Graphics.FillRectangle(BrushGraduates, _ New Rectangle(lblGraduates.Left, _ lblGraduates.Top + 18, _ btnClose.Width, 20)) e.Graphics.DrawRectangle(New Pen(Color.Black), _ New Rectangle(lblGraduates.Left - 1, _ lblGraduates.Top + 18, _ btnClose.Width, 20)) e.Graphics.FillRectangle(brushUndergraduates, _ New Rectangle(btnClose.Left, _ lblUndergraduates.Top + 18, _ btnClose.Width, 20)) e.Graphics.DrawRectangle(New Pen(Color.Black), _ New Rectangle(btnClose.Left - 1, _ lblUndergraduates.Top + 18, _ btnClose.Width + 1, 20)) e.Graphics.FillRectangle(brushCertificates, _ New Rectangle(btnClose.Left, _ lblCertificates.Top + 18, _ btnClose.Width, 20)) e.Graphics.DrawRectangle(New Pen(Color.Black), _ New Rectangle(btnClose.Left - 1, _ lblCertificates.Top + 18, _ btnClose.Width + 1, 20)) pbxChart.CreateGraphics().DrawPie(New Pen(Color.Blue), _ 0.0F, 0.0F, 260.0F, _ 200.0F, 0.0F, Graduates) pbxChart.CreateGraphics().DrawPie(New Pen(Color.Red), _ 0.0F, 0.0F, 260.0F, _ 200.0F, Graduates, Undergraduates) pbxChart.CreateGraphics().DrawPie(New Pen(Color.Green), _ 0.0F, 0.0F, 260.0F, _ 200.0F, Graduates + Undergraduates, _ Certificates) pbxChart.CreateGraphics().DrawEllipse(New Pen(Color.Red, 2), _ New Rectangle(0.0F, 0.0F, 260.0F, 200)) End Sub

28. In the Class Name combo box, select pbxChart
29. In the Method Name combo box, select Paint and implement the event as follows:
     

    Private Sub pbxChart_Paint(ByVal sender As Object, _ ByVal e As System.Windows.Forms.PaintEventArgs) _ Handles pbxChart.Paint Invalidate() End Sub

30. In the Class Name combo box, select btnCreateChart
31. In the Method Name combo box, select Click and implement the event as follows:
     

    Private Sub btnCreateChart_Click(ByVal sender As Object, _ ByVal e As System.EventArgs) _ Handles btnCreateChart.Click Dim grad As Single Dim under As Single Dim cert As Single Dim total As Single Dim percentGraduates As Single Dim percentUndergraduates As Single Dim percentCertificates As Single Try grad = CSng(txtGraduates.Text) Catch MsgBox("Invalid Value") End Try Try under = CSng(txtUndergraduates.Text) Catch MsgBox("Invalid Value") End Try Try cert = CSng(txtCertificates.Text) Catch MsgBox("Invalid Value") End Try total = grad + under + cert percentGraduates = (grad / total) * 100 percentUndergraduates = (under / total) * 100 percentCertificates = (cert / total) * 100 Graduates = (360 * percentGraduates) / 100 Undergraduates = (360 * percentUndergraduates) / 100 Certificates = (360 * percentCertificates) / 100 pbxChart.Invalidate() End Sub

32. Execute the application and test the form
     
     
33. After using it, close the form

A gradient brush resembles a solid brush in that it is color-based. Unlike a solid brush, a gradient brush uses two colors. Its main characteristic is that, when used, one color is applied on one side and the other color is applied to the other side. In between, both colors merge to create a transition or fading effect.

There are two types of gradient brushes: linear and path.

A linear gradient is used to apply two colors in a closed shape but from one side of the shape, such as the left, to the other opposite side of the shape, such as the right.

To support linear gradient brushes, the .NET Framework provides the LinearGradientBrush class defined in the System.Drawing.Drawing2D namespace. To specify the starting and the end points inside of the shape that you want to fill, you can use one of the following constructors:

Public Sub New(point1 As Point, _
	         point2 As Point, _
	         color1 As Color, _
	         color2 As Color)
Public Sub New(point1 As PointF, _
	         point2 As PointF, _
	         color1 As Color, _
	         color2 As Color)

The first argument, point1, is the point where the drawing would start. The third argument, color1, is the color that would be applied from that point. The second argument, point2, is the point where the drawing would end by applying the color specified by the fourth argument, color2.

Here is an example:

Imports System.Drawing
Imports System.Drawing.Drawing2D
Imports System.Windows.Forms

Module Exercise

    Public Class Starter
        Inherits Form

        Dim components As System.ComponentModel.Container

        Public Sub New()
            InitializeComponent()
        End Sub

        Public Sub InitializeComponent()

        End Sub

        Private Sub FormPaint(ByVal sender As Object, _
                              ByVal e As PaintEventArgs) _
                              Handles MyBase.Paint

            Dim lgb As LinearGradientBrush = _
                 New LinearGradientBrush(New Point(20, 20), _
                                         	           New Point(450, 20), _
                                         	           Color.DarkGreen, _
                                         	           Color.LightBlue)
            e.Graphics.FillRectangle(lgb, 20, 20, 430, 180)

        End Sub
    End Class

    Function Main() As Integer

        Dim frmStart As Starter = New Starter

        Application.Run(frmStart)

        Return 0
    End Function

End Module

By default, the linear gradient brush fills its gradient based on a horizontal line. If you want the color merge to use a different orientation, such as vertical or diagonal, you can use one of the following constructors:

Public Sub New(rect As Rectangle, _
	          color1 As Color, _
	          color2 As Color, _
	          linearGradientMode As LinearGradientMode)
Public Sub New(rect As RectangleF, _
	         color1 As Color, _
	         color2 As Color, _
	         linearGradientMode As LinearGradientMode)

The first argument, rect, is the rectangle inside of which the colors would be applied. The second argument, color1, is the color that would be applied from a starting point. The second argument, color2, is the color that would be applied at the other end. The factor argument is used to determine the orientation of the merging colors. It has the following members:

Vertical: The first color, color1,  is applied to the top section of the rect argument. The second color, color2,  is applied to the bottom section of the rect argument:

Private Sub FormPaint(ByVal sender As Object, _
                              ByVal e As PaintEventArgs) _
                              Handles MyBase.Paint

            Dim rect As Rectangle = New Rectangle(10, 10, 470, 300)
            Dim lgb As LinearGradientBrush = _
                   New LinearGradientBrush(rect, _
                                                    Color.DarkRed, _
                                             Color.White, _
                     LinearGradientMode.Vertical)
            e.Graphics.FillRectangle(lgb, 10, 10, 450, 280)

End Sub

Horizontal: The first color, color1,  is applied to the left section of the rect argument. The second color, color2,  is applied to the right section of the rect argument

BackwardDiagonal: The first color, color1,  is applied to the top-right corner of the rect argument. The second color, color2,  is applied to the bottom-left corner of the rect argument:

ForwardDiagonal: The first color, color1,  is applied to the top-left corner of the rect argument. The second color, color2, is applied to the bottom-right corner of the rect argument:

The constructor used to produce the above orientation has the limitation that it provides only four options. If you want, you can apply any angular merge as you see fit. To do this, you can use one of the following constructors:

Public Sub New(rect As Rectangle, _
	         color1 As Color, _
	         color2 As Color, _
	         angle As Single)
Public Sub New(rect As RectangleF, _
	         color1 As Color, _
	         color2 As Color, _
	         angle As Single)

The first argument, rect, is the rectangle inside of which the colors would be applied. The last argument, angle, is an angle measured clockwise, that will specify the orientation of the merging colors The second argument, color1, is the color that would be applied from the starting point. The second argument, color2, is the color that would be applied at the other end. Here is an example:

Private Sub FormPaint(ByVal sender As Object, _
                              ByVal e As PaintEventArgs) _
                              Handles MyBase.Paint

            Dim rect As Rectangle = New Rectangle(10, 10, 470, 300)
            Dim lgb As LinearGradientBrush = New LinearGradientBrush(rect, _
                                                         Color.DarkRed, _
                                                         Color.White, -65.24F)
            e.Graphics.FillRectangle(lgb, 10, 10, 450, 280)

End Sub

1. Reopen the YearlySales2 project and change the Click event of the Generate button as follows:
    

   Private Sub btnGenerate_Click(ByVal sender As Object, _ ByVal e As System.EventArgs) _ Handles btnGenerate.Click ' Retrieve the values of the current year's sales Dim CurQtr1 As Integer Dim CurQtr2 As Integer Dim CurQtr3 As Integer Dim CurQtr4 As Integer Try CurQtr1 = CInt(txtCurrentQtr1.Text) / 100 Catch MsgBox("Invalid Value") End Try Try CurQtr2 = CInt(txtCurrentQtr2.Text) / 100 Catch MsgBox("Invalid Value") End Try Try CurQtr3 = CInt(txtCurrentQtr3.Text) / 100 Catch MsgBox("Invalid Value") End Try Try CurQtr4 = CInt(txtCurrentQtr4.Text) / 100 Catch MsgBox("Invalid Value") End Try ' Create an array of Rectangle objects for the current year Dim RectCurrentYear As Rectangle() = { _ New Rectangle(txtCurrentQtr1.Left + 20, _ 380 - CurQtr1, 40, CurQtr1), _ New Rectangle(txtCurrentQtr2.Left + 20, _ 380 - CurQtr2, 40, CurQtr2), _ New Rectangle(txtCurrentQtr3.Left + 20, _ 380 - CurQtr3, 40, CurQtr3), _ New Rectangle(txtCurrentQtr4.Left + 20, _ 380 - CurQtr4, 40, CurQtr4)} ' Retrieve the values of last year's sales Dim PrvQtr1 As Integer Dim PrvQtr2 As Integer Dim PrvQtr3 As Integer Dim PrvQtr4 As Integer Try PrvQtr1 = CInt(txtPreviousQtr1.Text) / 100 Catch MsgBox("Invalid Value") End Try Try PrvQtr2 = CInt(txtPreviousQtr2.Text) / 100 Catch MsgBox("Invalid Value") End Try Try PrvQtr3 = CInt(txtPreviousQtr3.Text) / 100 Catch MsgBox("Invalid Value") End Try Try PrvQtr4 = CInt(txtPreviousQtr4.Text) / 100 Catch MsgBox("Invalid Value") End Try ' Create an array of Rectangle objects for the previous year Dim RectPreviousYear As Rectangle() = { _ New Rectangle(txtPreviousQtr1.Left + 30, _ 380 - PrvQtr1, 40, PrvQtr1), _ New Rectangle(txtPreviousQtr2.Left + 30, _ 380 - PrvQtr2, 40, PrvQtr2), _ New Rectangle(txtPreviousQtr3.Left + 30, _ 380 - PrvQtr3, 40, PrvQtr3), _ New Rectangle(txtPreviousQtr4.Left + 30, _ 380 - PrvQtr4, 40, PrvQtr4)} ' In case the user has changed the values, erase the previous chart GraphDrawingArea.Clear(BackColor) Dim rect As Rectangle = New Rectangle(10, 190, 300, 210) Dim linGradBrush As LinearGradientBrush = _ New LinearGradientBrush(rect, _ Color.FromArgb(204, 102, 0), _ Color.AntiqueWhite, _ LinearGradientMode.Vertical) GraphDrawingArea.FillRectangle(linGradBrush, rect) GraphDrawingArea.DrawRectangle(New Pen(Color.Black), rect) Dim brushDiagCross As HatchBrush = _ New HatchBrush(HatchStyle.DiagonalCross, _ Color.White, Color.Blue) Dim brushDotDiamond As HatchBrush = _ New HatchBrush(HatchStyle.DottedDiamond, _ Color.Fuchsia, Color.Brown) ' Draw the chart for the previous year first to send it back GraphDrawingArea.FillRectangles(brushDiagCross, _ RectPreviousYear) GraphDrawingArea.DrawRectangles(New Pen(Color.Blue), _ RectPreviousYear) ' Draw the chart for the current year in front GraphDrawingArea.FillRectangles(brushDotDiamond, _ RectCurrentYear) GraphDrawingArea.DrawRectangles(New Pen(Color.Red), _ RectCurrentYear) ' Draw the small rectangles of the legend GraphDrawingArea.FillRectangle(brushDotDiamond, _ lblCurYear.Left - 30, _ lblCurYear.Top, 20, 14) GraphDrawingArea.DrawRectangle(New Pen(Color.Red), _ lblCurYear.Left - 30, _ lblCurYear.Top, 20, 14) GraphDrawingArea.FillRectangle(brushDiagCross, _ lblLastYear.Left - 30, _ lblLastYear.Top, 20, 14) GraphDrawingArea.DrawRectangle(New Pen(Color.Blue), _ lblLastYear.Left - 30, _ lblLastYear.Top, 20, 14) GraphDrawingArea.DrawRectangle(New Pen(Color.Black), _ 25, 380, Width - 220, 1) Invalidate() End Sub

2. Execute the application to test it:
    
   
3. After using the form, close it

The second type of gradient brush available is referred to as path gradient. This brush is applied on a path created by connecting a series of points to get a closed shape.  The interior of the shape can then be filled as a gradient.

To support path brushes, the .NET Framework provides the PathGradientBrush from the System.Drawing.Drawing2D namespace. Two of the constructors of this class are:

Public Sub New(points As Point())
Public Sub New(points As PointF())

The argument passed to this constructor is an array of type Point. Here is an example:

Imports System.Drawing
Imports System.Drawing.Drawing2D
Imports System.Windows.Forms

Module Exercise

    Public Class Starter
        Inherits Form

        Dim components As System.ComponentModel.Container

        Public Sub New()
            InitializeComponent()
        End Sub

        Public Sub InitializeComponent()

        End Sub

        Private Sub FormPaint(ByVal sender As Object, _
                              ByVal e As PaintEventArgs) _
                              Handles MyBase.Paint

            Dim ptGraph As Point() = { _
                    New Point(10, 10), _
                    New Point(450, 10), _
                    New Point(450, 250), _
                    New Point(10, 250)}

            Dim pgb As PathGradientBrush = New PathGradientBrush(ptGraph)
            e.Graphics.FillRectangle(pgb, 10, 10, 450, 280)

        End Sub
    End Class

    Function Main() As Integer

        Dim frmStart As Starter = New Starter

        Application.Run(frmStart)

        Return 0
    End Function

End Module