C# Winform Programming (8) GDI+ Drawing

GDI + Drawing

• Introduction
• System.Drawing namespace
• • Common classes in the System.Drawing namespace:
  • Common structures in the System.Drawing namespace:
• Graphics class
• Pen class
• Brush class
• Font class
• PictureBox image control
• Bitmap class

Introduction

GDI (Graphics Device Interface) image device interface, which is a drawing API. The System.Drawing namespace provides access to the basic graphics functions of GDI+.

System.Drawing namespace

Common classes in the System.Drawing namespace:

Class	Description
Bitmap	Encapsulates a GDI+ bitmap that consists of the pixel data of a graphics image and its properties.
Brush	Brush, defines internal objects used to fill graphic shapes (such as rectangles, ellipses, pie charts, polygons and closed paths)
Font	Font, defines a specific text format, including: font, font size and font style attributes. This class cannot be inherited
Graphics	Encapsulates a GDI+ drawing surface. This class cannot be inherited
Pen	Brush, which defines an object used to draw straight lines and curves. This class cannot be inherited
Region	Indicates the interior of a graphic shape composed of a rectangle and a path. This class cannot be inherited

Common structures in the System.Drawing namespace:

Structure	Description
Color	Represents RGB color
Point	Represents an ordered pair of points, integer X and Y coordinates defined in a two-dimensional plane
Rectangle	Stores a set of 4 integers, representing the position and size of a rectangle
Size	Stores an ordered pair of integers, usually the width and height of a rectangle

Graphics class

The Graphics class encapsulates a GDI + drawing interface and provides methods for drawing objects to display devices.
Common methods of the Graphics class:

Name	Description
Dispose	Releases all resources used by Graphics
DrawEllipse	Draws an ellipse defined by a border specified by a pair of coordinates, height and width
DrawArc	Draw an arc
DrawLine	Draw a straight line
td>
DrawPolygon	Draw a polygon defined by a set of Point structures
DrawRectangle	Draw a rectangle specified by a coordinate pair, width and height
DrawPie	Draw a sector shape specified by a coordinate pair, width, height and two The ellipse definition specified by the sky ray
DrawCurse	Draw a curve, specified by the parameter Point array
FillEllips	Fills the interior of an ellipse defined by a border specified by a pair of coordinates, a width and a height
FillRegion	Fill the interior of the Region
ScaleTransform	Apply the specified scaling operation to this Graphics
TanslateTransform	Translation coordinate system origin

Pen class

The Pen class can set the color of the brush, the thickness of the line and the style of the line (realization, dashed line, etc.). The brush is the tool for drawing, and the Graphics object is the place for drawing.

Brush class

Brush class (brush), used to fill graphics. This class is an abstract base class and cannot be instantiated directly.
Derived classes of the Brush class:

Name	Description
ImageBrush	Image drawing area
LinearGradientBrush	Linear gradient drawing area
RadialGradientBrush	Radial gradient drawing area, the focus defines the beginning of the gradient, and the ellipse defines the focus of the gradient
SolidColorBrush	Single color drawing area
VideoBrush	Video content drawing area

Font class

Font class, when drawing text, you can set the font style, size, and font type.

using System.Drawing.Drawing2D;
using System.Numerics;
using System.Security.Cryptography.Xml;
using System.Threading;


namespace GDIDemo
{<!-- -->
    public partial class Form1 : Form
    {<!-- -->
        public Form1()
        {<!-- -->
            InitializeComponent();
        }

        /// <summary>
        /// Draw a straight line
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button1_Click(object sender, EventArgs e)
        {<!-- -->
            Graphics g = this.CreateGraphics();
            Pen p = new Pen(Color.Black);
            g.DrawLine(p, 0, this.Height / 2, this.Width, this.Height / 2);
            p.Dispose();
            g.Dispose();
        }


        /// <summary>
        /// Draw a rectangle
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button2_Click(object sender, EventArgs e)
        {<!-- -->
            Graphics g = this.CreateGraphics();
            Pen p = new Pen(Color.Red);
            g.DrawRectangle(p, 50, 50, 200, 200);
            p.Dispose();
            g.Dispose();
        }

        /// <summary>
        /// Draw a circle
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button3_Click(object sender, EventArgs e)
        {<!-- -->
            Graphics g = this.CreateGraphics();
            Pen p = new Pen(Color.Blue);
            g.DrawEllipse(p, 50, 50, 100, 100);
            p.Dispose();
            g.Dispose();
        }

        /// <summary>
        /// Draw a cylinder
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button4_Click(object sender, EventArgs e)
        {<!-- -->
            int height = this.ClientSize.Height - 100;
            int width = this.ClientSize.Width - 50;
            int vHeight = 200;
            int vWidth = 100;

            Graphics g = this.CreateGraphics();
            g.Clear(Color.White);
            Pen pen = new Pen(Color.Gray);
            SolidBrush brush = new SolidBrush(Color.Gainsboro);
            for (int i = height / 2; i > 0; i--)
            {<!-- -->
                g.DrawEllipse(pen, width / 2, i, vHeight, vWidth);
            }
            g.FillEllipse(brush, width / 2, 0, vHeight, vWidth);
        }

        /// <summary>
        /// Draw a filled rectangle
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button5_Click(object sender, EventArgs e)
        {<!-- -->
            Graphics g = this.CreateGraphics();
            Pen pen = new Pen(Color.Blue);
            Brush brush = pen.Brush;
            Rectangle rect = new Rectangle(50, 50, 100, 100);
            g.FillRectangle(brush, rect);
            pen.Dispose();
            g.Dispose();
        }

        /// <summary>
        /// Draw a gradient circle
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button6_Click(object sender, EventArgs e)
        {<!-- -->
            Graphics g = this.CreateGraphics();
            Rectangle rect = new Rectangle(150, 50, 200, 200);
            LinearGradientBrush brush = new LinearGradientBrush(rect, Color.Orange, Color.Purple, 90);
            g.FillEllipse(brush, rect);
            brush.Dispose();
            g.Dispose();
        }

        /// <summary>
        /// Draw text
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button7_Click(object sender, EventArgs e)
        {<!-- -->
            Graphics g = this.CreateGraphics();
            Pen pen = new Pen(Color.Blue);
            Font f = new Font("official script", 24, FontStyle.Italic);
            g.DrawString("Windows Application Design", f, pen.Brush, 50, 50);
            pen.Dispose();
            g.Dispose();
        }


        private void button9_Click(object sender, EventArgs e)
        {<!-- -->
            using (Graphics g = this.CreateGraphics())
            {<!-- -->
                g.Clear(Color.White);
            }
        }
        private void Form1_Paint(object sender, PaintEventArgs e)
        {<!-- -->
#if false
            Graphics g = this.CreateGraphics();
            g.Clear(Color.White);
            Pen myPen = new Pen(Color.Red, 3);
            g.DrawRectangle(myPen, 0, 0, 200, 100);
            g.DrawEllipse(myPen, 0, 0, 200, 100);
            g.Dispose();
            myPen.Dispose();
#endif
        }

        /// <summary>
        /// Coordinate translation
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button8_Click(object sender, EventArgs e)
        {<!-- -->

            Graphics g = this.CreateGraphics();
            g.Clear(Color.White);
            Pen myPen = new Pen(Color.Red, 3);

            g.DrawRectangle(myPen, 0, 0, 200, 100);
            g.DrawEllipse(myPen, 0, 0, 200, 100);
            Thread.Sleep(1000);

            g.Clear(Color.White);
            g.TranslateTransform(30, 30);
            g.DrawRectangle(myPen, 0, 0, 200, 100);
            g.DrawEllipse(myPen, 0, 0, 200, 100);
            g.Dispose();
            myPen.Dispose();
        }

        /// <summary>
        /// Coordinate scaling
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button10_Click(object sender, EventArgs e)
        {<!-- -->
            Graphics g = this.CreateGraphics();
            g.Clear(Color.White);
            Pen myPen = new Pen(Color.Red, 3);
            g.DrawRectangle(myPen, 0, 0, 200, 100);
            g.DrawEllipse(myPen, 0, 0, 200, 100);
            Thread.Sleep(1000);

            g.Clear(Color.White);
            g.ScaleTransform(1.5f, 2.0f); // The horizontal axis is enlarged to 1.5 times and the vertical axis is enlarged to 2 times
            g.DrawRectangle(myPen, 0, 0, 200, 100);
            g.DrawEllipse(myPen, 0, 0, 200, 100);
            g.Dispose();
            myPen.Dispose();


        }

        /// <summary>
        /// Draw waveform
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>

        private void button11_Click(object sender, EventArgs e)
        {<!-- -->
            Graphics g = this.CreateGraphics();
            g.Clear(Color.White);
            Pen pen = new Pen(Color.Blue, 3);
            Point p1 = new Point(30, this.ClientSize.Height - 200);
            Point p2 = new Point(this.ClientSize.Width - 100, this.ClientSize.Height - 200);
            Point p3 = new Point(30, 30);
            g.DrawLine(pen, p1, p2);
            g.DrawLine(pen, p1, p3);
            Font f = new Font("宋体", 12, FontStyle.Bold);
            g.DrawString("x", f, pen.Brush, p2);
            g.DrawString("y", f, pen.Brush, 10, 10);


            double x1, x2, y1, y2, a;
            x1 = x2 = y1 = y2 = 0;
            y2 = this.ClientSize.Height - 200;
            for (x2 = 0; x2 <this.ClientSize.Width; x2 + + )
            {<!-- -->
                a = 2 * Math.PI * x2 / this.ClientSize.Width;
                y2 = Math.Sin(a);
                y2 = (1 - y2) * (this.ClientSize.Height - 200) / 2;
                g.DrawLine(pen, (int)(x1 + 30), (int)y1, (int)(x2 + 30), (int)y2);
                x1 = x2;
                y1 = y2;
            }


        }

        /// <summary>
        /// Draw a pie chart
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button12_Click(object sender, EventArgs e)
        {<!-- -->
            Graphics g = this.CreateGraphics();
            Rectangle rect = new Rectangle(50, 50, 200, 100);
            Brush brush = new SolidBrush(Color.Blue);
            g.FillPie(brush, rect, 0, 60);
            g.FillPie(brush, rect, 60, 150);
            brush = new SolidBrush(Color.Yellow);
            g.FillPie(brush, rect, 210, 150);
            brush.Dispose();
            g.Dispose();
        }
    }
}

PictureBox image control

PictureBox control, the picture box is a basic control for operating graphics and images. It is mainly used to display and save graphics and image information. Its main attribute methods are:

• Attributes:
  • Image: Set or get the image displayed with this control
  • SizeMode: Indicates how to display the image
• method:
  • Load: display image

Bitmap class

Bitmap class encapsulates GDI + bitmap. This bitmap consists of pixel data of the graphic image and its attributes. Bitmap is an object used to process images defined by pixel data. Its common properties and methods are:

Name	Description
Size	Get the width and height of the image in pixels
Width	Get the width of the image
Height	Get the height of the image
FromFile()	Create an image from the specified file
FromStream()	Create an image from the specified data stream
GetPixel	Get this Bitmap Specify the color of the pixel
MakeTransparent	Make the default transparent color transparent to this Bitmap
Save	Save this image in the specified format to the specified stream
RotateFlip	Rotate, mirror, or both rotate and mirror Image

        /// <summary>
        /// Create a bitmap and save it as a picture
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button13_Click(object sender, EventArgs e)
        {<!-- -->
            Bitmap bm = new Bitmap(this.ClientSize.Width, this.ClientSize.Height,
                System.Drawing.Imaging.PixelFormat.Format32bppArgb);
            Graphics g = Graphics.FromImage(bm);

            Font f = new Font("official script", 24, FontStyle.Italic);
            Pen pen = new Pen(Color.OrangeRed);
            g.DrawString("Create bitmap test save image", f, pen.Brush, 0, 0);
            pictureBox1.Image = bm;
            pictureBox1.Show();

            bm.Save("c:\temp\1.bmp");
            pen.Dispose();
            g.Dispose();
        }

        /// <summary>
        /// Load the image and save the image
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button14_Click(object sender, EventArgs e)
        {<!-- -->
            OpenFileDialog openfile = new OpenFileDialog();
            openfile.Filter = "Image file *.bmp|*.bmp|*.jpg|*.png";
            if (openfile.ShowDialog() == DialogResult.OK)
            {<!-- -->
                pictureBox1.Image = Image.FromFile(openfile.FileName);
                pictureBox1.Image.Save("c:\temp\2.bmp");
            }
        }