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GDI+ Brushes: Solid Brushes

   

Fundamentals of Brushes

 

Introduction

A brush is an object that holds a color, a picture, or a drawing pattern and that is used to fill the interior of a closed shape. This definition also means that there are various types of brushes with different goals. To meet these goals, the .NET Framework provides support for brushes in various namespaces with different classes. The parent of all brushes is the Brush class defined in the System.Drawing namespace.

     

Using a Brush

Because the main job of a brush is to fill a closed shape, the Graphics class provides a method that corresponds to each of the closed shapes we reviewed to draw in the previous lesson in order to fill it. The methods are:

  • FillRectangle: Used to fill the interior of a rectangle or a square
  • FillRectangle: Used to fill the interior of a series of rectangles
  • FillEllipse: Used to fill the interior of an ellipse or a circle
  • FillPolygon: Used to fill the interior of a polygon
  • FillClosedCurve: Used to fill the interior of a closed curve
  • FillPie: Used to fill the interior of a pie
  • FillPath: Used to fill the interior of a graphic path

To fill out a shape, call one of these methods, pass it a brush value, followed by the location and dimensions of the shape. For example, if you want to draw a rectangle and fill it with a brush, you would use code similar to:

using System;
using System.Drawing;
using System.Windows.Forms;

public class Exercise : Form
{
    public Exercise()
    {
        InitializeComponent();
    }

    void InitializeComponent()
    {
        Paint += new PaintEventHandler(Exercise_Paint);
    }

    private void Exercise_Paint(object sender, PaintEventArgs e)
    {
        e.Graphics.FillRectangle(SomeBrush, 20, 20, 200, 160);
    }
}

public class Program
{
    public static int Main()
    {
        Application.Run(new Exercise());

        return 0;
    }
}

Over all, there are four types of brushes.

Solid Brushes

 

Simple Colored Brushes

Like a pen, the primary characteristic of a brush is its color. To help you create a simple brush, the System.Drawing namespace provides the static sealed Brushes class. The only feature this class provides is the ability to specify a color to use on a brush. As a static class, you never have to instantiate it.

To create a simple brush whose only information is provided by its color, call the Brushes class and access a color by qualifying it with the name of the class. Each color is provided by its name as a property. Here is an example of using the class:

private void Form1_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
{
    Point[] pt = { new Point(10,  22), new Point(188, 246),
                          new Point(280, 192), new Point(250,  48) };

    e.Graphics.FillClosedCurve(Brushes.BlanchedAlmond, pt);
    e.Graphics.DrawClosedCurve(Pens.Blue, pt);
}

This would produce:

Brush

ApplicationApplication: Drawing a Circle

  1. Start a new Windows Application named RotatingCircles1
  2. Double-click middle of the form and change the file as follows:
    using System;
    using System.Collections.Generic;
    using System.ComponentModel;
    using System.Data;
    using System.Drawing;
    using System.Linq;
    using System.Text;
    using System.Windows.Forms;
    
    namespace RotatingCircles1
    {
        public partial class Form1 : Form
        {
            Graphics graphDrawingArea;
            Bitmap bmpDrawingArea;
    
            public Form1()
            {
                InitializeComponent();
            }
    
            private void Form1_Load(object sender, EventArgs e)
            {
                bmpDrawingArea = new Bitmap(Width, Height);
                graphDrawingArea = Graphics.FromImage(bmpDrawingArea);
            }
        }
    }
  3. From the Components section of the Toolbox, click Timer and click the form
  4. In the Properties window, change the following values:
    Enabled: True
    Interval: 20
  5. Under the form, double-click the timer1 object and make the following changes:
    using System;
    using System.Collections.Generic;
    using System.ComponentModel;
    using System.Data;
    using System.Drawing;
    using System.Linq;
    using System.Text;
    using System.Windows.Forms;
    
    namespace RotatingCircles1
    {
        public partial class Form1 : Form
        {
            Graphics graphDrawingArea;
            Bitmap bmpDrawingArea;
            static int mainRadius = 10;
            static int smallRadius = 5;
            static bool isMax;
            static bool smallRadiusMax;
    
            public Form1()
            {
                InitializeComponent();
            }
    
            private void Form1_Load(object sender, EventArgs e)
            {
                bmpDrawingArea = new Bitmap(Width, Height);
                graphDrawingArea = Graphics.FromImage(bmpDrawingArea);
            }
    
            void DrawCentralCircle(int CenterX, int CenterY, int Radius)
            {
                int start = CenterX - Radius;
                int end = CenterY - Radius;
                int diam = Radius * 2;
    
                graphDrawingArea.DrawEllipse(new Pen(Color.Blue),
                              start, end, diam, diam);
            }
    
            void DrawCornerCircle(int CenterX, int CenterY, int Radius)
            {
                int start = CenterX - Radius;
                int end = CenterY - Radius;
                int diam = Radius * 2;
    
                graphDrawingArea.DrawEllipse(new Pen(Color.Red),
                              start, end, diam, diam);
            }
    
            private void timer1_Tick(object sender, EventArgs e)
            {
                Graphics graph = Graphics.FromHwnd(this.Handle);
    
                int centerX = ClientRectangle.Width / 2;
                int centerY = ClientRectangle.Height / 2;
    
                if (isMax == true)
                    mainRadius--;
                else
                    mainRadius++;
    
                if (mainRadius > (ClientRectangle.Height / 2))
                    isMax = true;
                if (mainRadius < 10)
                    isMax = false;
    
                if (smallRadiusMax == true)
                    smallRadius--;
                else
                    smallRadius++;
    
                if (smallRadius > 240)
                    smallRadiusMax = true;
                if (smallRadius < 5)
                    smallRadiusMax = false;
    
                graphDrawingArea.FillRectangle(Brushes.Black, 0, 0, Width, Height);
    
                // Central
                DrawCentralCircle(centerX, centerY, mainRadius);
                // Top-Left
                DrawCornerCircle(centerX / 2, centerY / 2, smallRadius);
                // Top-Right
                DrawCornerCircle(centerX + (centerX / 2), centerY / 2, smallRadius);
                // Bottom-Left
                DrawCornerCircle(centerX / 2, centerY + (centerY / 2), smallRadius);
                // BottomRight
                DrawCornerCircle(centerX + (centerX / 2),
                         centerY + (centerY / 2), smallRadius);
    
                graph.DrawImage(bmpDrawingArea, 0, 0);
            }
        }
    }
  6. Execute the application to see the result
     
    Rotating Circles
  7. Close the form

Creating a Solid Brush

The simplest type of brush is referred to as solid. This type of brush is simply equipped with a color and it is used to fill a shape with it. To get a solid brush, you use the SolidBrush class defined in the System.Drawing namespace. It has only one constructor declared with the following syntax:

public SolidBrush(Color color);

The color passed as argument must be a valid definition of a Color. Here is an example:

private void Exercise_Paint(object sender, PaintEventArgs e)
{
        SolidBrush brushBlue = new SolidBrush(Color.Blue);

        e.Graphics.FillRectangle(brushBlue, 20, 20, 200, 160);
}

This would produce:

Brush

If you plan to use different colors to fill different shapes, you don't have to create a new brush for each shape. At any time, before re-using the same brush previously defined, you can simply change its Color. For this reason, the SolidBrush class is equipped with the Color property. Here is an example of using it:

private void Exercise_Paint(object sender, PaintEventArgs e)
{
        SolidBrush colorizer = new SolidBrush(Color.Lime);
        e.Graphics.FillRectangle(colorizer, 10, 10, 120, 120);

        colorizer.Color = Color.Salmon;
        e.Graphics.FillRectangle(colorizer, 140, 10, 120, 120);

        colorizer.Color = Color.Aqua;
        e.Graphics.FillRectangle(colorizer, 10, 140, 120, 120);

        colorizer.Color = Color.Navy;
        e.Graphics.FillRectangle(colorizer, 140, 140, 120, 120);
}

This would produce:

Solid Brushes

Like most objects used in graphics programming, a brush consumes the computer resources. Therefore, after using it, you can free the resources it was using by calling the Dispose() method. Here is an example:

private void Exercise_Paint(object sender, PaintEventArgs e)
{
        SolidBrush colorizer = new SolidBrush(Color.Lime);
        e.Graphics.FillRectangle(colorizer, 10, 10, 120, 120);

        colorizer.Color = Color.Salmon;
        e.Graphics.FillRectangle(colorizer, 140, 10, 120, 120);

        colorizer.Color = Color.Aqua;
        e.Graphics.FillRectangle(colorizer, 10, 140, 120, 120);

        colorizer.Color = Color.Navy;
        e.Graphics.FillRectangle(colorizer, 140, 140, 120, 120);

    colorizer.Dispose();
}

ApplicationApplication: Using a Solid Brush

  1. Start a new Windows Forms Application named WeeklySales2
  2. Design the form as follows:
     
    Company Weekly Sales
    Control Name Text Other Properties
    Label Label   Monday  
    Label Label   Tuesday  
    Label Label   Wednesday  
    Label Label   Thursday  
    Label Label   Friday  
    TextBox TextBox txtMonday 12000 TextAlign: Right
    TextBox TextBox txtTuesday 11000 TextAlign: Right
    TextBox TextBox txtWednesday 8500 TextAlign: Right
    TextBox TextBox txtThursday 16800 TextAlign: Right
    TextBox TextBox txtFriday 17500 TextAlign: Right
    Button Button Generate btnGenerate  
  3. Double-click an unoccupied area of the form and change the file as follows:
    using System;
    using System.Collections.Generic;
    using System.ComponentModel;
    using System.Data;
    using System.Drawing;
    using System.Linq;
    using System.Text;
    using System.Windows.Forms;
    
    namespace WeeklySales2
    {
        public partial class Form1 : Form
        {
            Graphics graphDrawingArea;
            Bitmap bmpDrawingArea;
    
            public Form1()
            {
                InitializeComponent();
            }
    
            private void Form1_Load(object sender, EventArgs e)
            {
                bmpDrawingArea = new Bitmap(Width, Height);
                graphDrawingArea = Graphics.FromImage(bmpDrawingArea);
            }
        }
    }
  4. Return to the form and click an empty area on it. In the Properties window, click the Events button Events
  5. Double-click the Paint field and implement its event as follows:
    private void Form1_Paint(object sender, PaintEventArgs e)
    {
                e.Graphics.DrawImage(bmpDrawingArea, 0, 0);
    }
  6. Return to the form and double-click the Generate button
  7. Implement its Click event as follows:
    private void btnGenerate_Click(object sender, EventArgs e)
    {
                int monday = 0;
                int tuesday = 0;
                int wednesday = 0;
                int thursday = 0;
                int friday = 0;
    
                try
                {
                    monday = int.Parse(txtMonday.Text) / 100;
                }
                catch (FormatException)
                {
                    MessageBox.Show("Invalid value");
                }
    
                try
                {
                    tuesday = int.Parse(txtTuesday.Text) / 100;
                }
                catch (FormatException)
                {
                    MessageBox.Show("Invalid value");
                }
    
                try
                {
                    wednesday = int.Parse(txtWednesday.Text) / 100;
                }
                catch (FormatException)
                {
                    MessageBox.Show("Invalid value");
                }
    
                try
                {
                    thursday = int.Parse(txtThursday.Text) / 100;
                }
                catch (FormatException)
                {
                    MessageBox.Show("Invalid value");
                }
    
                try
                {
                    friday = int.Parse(txtFriday.Text) / 100;
                }
                catch (FormatException)
                {
                    MessageBox.Show("Invalid value");
                }
    
                graphDrawingArea.Clear(this.BackColor);
    
                graphDrawingArea.FillRectangle(new SolidBrush(Color.Red),
                        this.txtMonday.Left + 5,
                        280 - monday, 40, monday);
                graphDrawingArea.DrawRectangle(new Pen(Color.Black),
                        this.txtMonday.Left + 5,
                            280 - monday, 40, monday);
                graphDrawingArea.FillRectangle(new SolidBrush(Color.Blue),
                        this.txtTuesday.Left + 5,
                        280 - tuesday, 40, tuesday);
                graphDrawingArea.DrawRectangle(new Pen(Color.Black),
                        this.txtTuesday.Left + 5,
                            280 - tuesday, 40, tuesday);
                graphDrawingArea.FillRectangle(new SolidBrush(Color.Fuchsia),
                        this.txtWednesday.Left + 5,
                        280 - wednesday, 40, wednesday);
                graphDrawingArea.DrawRectangle(new Pen(Color.Black),
                        this.txtWednesday.Left + 5,
                        280 - wednesday, 40, wednesday);
                graphDrawingArea.FillRectangle(new SolidBrush(Color.Brown),
                        this.txtThursday.Left + 5,
                        280 - thursday, 40, thursday);
                graphDrawingArea.DrawRectangle(new Pen(Color.Black),
                        this.txtThursday.Left + 5,
                        280 - thursday, 40, thursday);
                graphDrawingArea.FillRectangle(new SolidBrush(Color.Turquoise),
                        this.txtFriday.Left + 5,
                        280 - friday, 40, friday);
                graphDrawingArea.DrawRectangle(new Pen(Color.Black),
                        this.txtFriday.Left + 5,
                            280 - friday, 40, friday);
    
                graphDrawingArea.DrawRectangle(new Pen(Color.Black),
                        10, 280, Width - 30, 1);
                Invalidate();
    }
  8. Execute the application and test the form
     
     Weekly Sales
  9. After using it, close the form
 

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