docs-desktop/dotnet-desktop-guide/framework/winforms/advanced/how-to-create-graphics-objects-for-drawing.md

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How to: Create Graphics Objects for Drawing	Learn now to create a Graphic object that you need to draw lines and shapes, render text, or display and manipulate images with GDI+.	03/30/2017	csharp vb cpp	graphics [Windows Forms], creating images [Windows Forms], creating GDI+, creating images	162861f9-f050-445e-8abb-b2c43a918b8b

How to: Create Graphics Objects for Drawing

Before you can draw lines and shapes, render text, or display and manipulate images with GDI+, you need to create a xref:System.Drawing.Graphics object. The xref:System.Drawing.Graphics object represents a GDI+ drawing surface, and is the object that is used to create graphical images.

There are two steps in working with graphics:

1. Creating a xref:System.Drawing.Graphics object.

2. Using the xref:System.Drawing.Graphics object to draw lines and shapes, render text, or display and manipulate images.

Creating a Graphics Object

A graphics object can be created in a variety of ways.

To create a graphics object

• Receive a reference to a graphics object as part of the xref:System.Windows.Forms.PaintEventArgs in the xref:System.Windows.Forms.Control.Paint event of a form or control. This is usually how you obtain a reference to a graphics object when creating painting code for a control. Similarly, you can also obtain a graphics object as a property of the xref:System.Drawing.Printing.PrintPageEventArgs when handling the xref:System.Drawing.Printing.PrintDocument.PrintPage event for a xref:System.Drawing.Printing.PrintDocument.

  -or-

• Call the xref:System.Windows.Forms.Control.CreateGraphics%2A method of a control or form to obtain a reference to a xref:System.Drawing.Graphics object that represents the drawing surface of that control or form. Use this method if you want to draw on a form or control that already exists.

  -or-

• Create a xref:System.Drawing.Graphics object from any object that inherits from xref:System.Drawing.Image. This approach is useful when you want to alter an already existing image.

  The following sections give details about each of these processes.

PaintEventArgs in the Paint Event Handler

When programming the xref:System.Windows.Forms.PaintEventHandler for controls or the xref:System.Drawing.Printing.PrintDocument.PrintPage for a xref:System.Drawing.Printing.PrintDocument, a graphics object is provided as one of the properties of xref:System.Windows.Forms.PaintEventArgs or xref:System.Drawing.Printing.PrintPageEventArgs.

To obtain a reference to a Graphics object from the PaintEventArgs in the Paint event

1. Declare the xref:System.Drawing.Graphics object.

2. Assign the variable to refer to the xref:System.Drawing.Graphics object passed as part of the xref:System.Windows.Forms.PaintEventArgs.

3. Insert code to paint the form or control.

   The following example shows how to reference a xref:System.Drawing.Graphics object from the xref:System.Windows.Forms.PaintEventArgs in the xref:System.Windows.Forms.Control.Paint event:

   Private Sub Form1_Paint(sender As Object, pe As PaintEventArgs) Handles _  
      MyBase.Paint  
      ' Declares the Graphics object and sets it to the Graphics object  
      ' supplied in the PaintEventArgs.  
      Dim g As Graphics = pe.Graphics  
      ' Insert code to paint the form here.  
   End Sub  
   

   private void Form1_Paint(object sender,
      System.Windows.Forms.PaintEventArgs pe)
   {  
      // Declares the Graphics object and sets it to the Graphics object  
      // supplied in the PaintEventArgs.  
      Graphics g = pe.Graphics;  
      // Insert code to paint the form here.  
   }  
   

   private:  
      void Form1_Paint(System::Object ^ sender,  
         System::Windows::Forms::PaintEventArgs ^ pe)  
      {  
         // Declares the Graphics object and sets it to the Graphics object  
         // supplied in the PaintEventArgs.  
         Graphics ^ g = pe->Graphics;  
         // Insert code to paint the form here.  
      }  
   

CreateGraphics Method

You can also use the xref:System.Windows.Forms.Control.CreateGraphics%2A method of a control or form to obtain a reference to a xref:System.Drawing.Graphics object that represents the drawing surface of that control or form.

To create a Graphics object with the CreateGraphics method

• Call the xref:System.Windows.Forms.Control.CreateGraphics%2A method of the form or control upon which you want to render graphics.

  Dim g as Graphics  
  ' Sets g to a Graphics object representing the drawing surface of the  
  ' control or form g is a member of.  
  g = Me.CreateGraphics  
  

  Graphics g;  
  // Sets g to a graphics object representing the drawing surface of the  
  // control or form g is a member of.  
  g = this.CreateGraphics();  
  

  Graphics ^ g;  
  // Sets g to a graphics object representing the drawing surface of the  
  // control or form g is a member of.  
  g = this->CreateGraphics();  
  

Create from an Image Object

Additionally, you can create a graphics object from any object that derives from the xref:System.Drawing.Image class.

To create a Graphics object from an Image

• Call the xref:System.Drawing.Graphics.FromImage%2A?displayProperty=nameWithType method, supplying the name of the Image variable from which you want to create a xref:System.Drawing.Graphics object.

  The following example shows how to use a xref:System.Drawing.Bitmap object:

  Dim myBitmap as New Bitmap("C:\Documents and Settings\Joe\Pics\myPic.bmp")  
  Dim g as Graphics = Graphics.FromImage(myBitmap)  
  

  Bitmap myBitmap = new Bitmap(@"C:\Documents and
     Settings\Joe\Pics\myPic.bmp");  
  Graphics g = Graphics.FromImage(myBitmap);  
  

  Bitmap ^ myBitmap = gcnew  
     Bitmap("D:\\Documents and Settings\\Joe\\Pics\\myPic.bmp");  
  Graphics ^ g = Graphics::FromImage(myBitmap);  
  

Note

You can only create xref:System.Drawing.Graphics objects from nonindexed .bmp files, such as 16-bit, 24-bit, and 32-bit .bmp files. Each pixel of nonindexed .bmp files holds a color, in contrast to pixels of indexed .bmp files, which hold an index to a color table.

Drawing and Manipulating Shapes and Images

After it is created, a xref:System.Drawing.Graphics object may be used to draw lines and shapes, render text, or display and manipulate images. The principal objects that are used with the xref:System.Drawing.Graphics object are:

• The xref:System.Drawing.Pen class—Used for drawing lines, outlining shapes, or rendering other geometric representations.

• The xref:System.Drawing.Brush class—Used for filling areas of graphics, such as filled shapes, images, or text.

• The xref:System.Drawing.Font class—Provides a description of what shapes to use when rendering text.

• The xref:System.Drawing.Color structure—Represents the different colors to display.

To use the Graphics object you have created

• Work with the appropriate object listed above to draw what you need.

  For more information, see the following topics:

  To render	See
  Lines	How to: Draw a Line on a Windows Form
  Shapes	How to: Draw an Outlined Shape
  Text	How to: Draw Text on a Windows Form
  Images	How to: Render Images with GDI+

See also

• Getting Started with Graphics Programming
• Graphics and Drawing in Windows Forms
• Lines, Curves, and Shapes
• How to: Render Images with GDI+