Windows Graphics Device Interface Plus GDI gdiplus'dll

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Windows Graphics Device Interface
PlusGDIgdiplus.dll
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Microsoft Windows GDI

• Graphics Device Interface
• two-dimensional vector graphics
• Imaging
• Typography
• GDI is on Windows XP and Windows Server 2003
• GDI improves on Windows Graphics Device
  Interface (GDI)
• GDI was included with earlier versions of Windows
• backwards compatibility with (plain old) GDI is
  present
• GDI adds new features and speeds up existing
  features

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overview of GDI

• .NET class libraries
• System.Drawing
• System.Drawing.Drawing2D
• GDI allows application programmers to display
  information on a screen or printer without
  knowing about a particular display device
• the programmer calls methods provided by GDI
  classes and those methods in turn make the
  appropriate calls to specific device drivers
• GDI insulates the application from the graphics
  hardware
• this insulation that allows developers to create
  device-independent applications

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3 parts to GDI

• Windows GDI offers three broad capabilities
• 2-D vector graphics
• imaging
• typography

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2-D vector graphics

• Vector graphics
• drawing lines, curves, and figures that are
  specified by sets of points on a coordinate
  system
• a straight line can be specified by its two
  endpoints
• a rectangle can be specified by a point giving
  the location of its upper-left corner and a pair
  of numbers giving its width and height
• a path can be specified by an array of points to
  be connected by straight lines
• a Bezier spline is a sophisticated curve
  specified by four control points
• GDI provides
• classes that store information about location
• the Rectangle class stores the location and size
  of a rectangle
• the Point class stores a pixel location on the
  screen
• classes that store information about how to draw
• the Pen class stores information about line
  color, width, and style
• several Brush classes store information about how
  closed figures are to be filled with colors or
  patterns
• a class that actually does the drawing
• the Graphics class has methods for drawing lines,
  rectangles, paths, and other figures

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imaging

• some pictures are difficult or impossible to
  display with the techniques of vector graphics.
• i.e., pictures on buttons or icons would be
  difficult to specify as collections of lines and
  curves
• a photograph of a crowd would be even more
  difficult to create with vector graphics
• images of this type are stored as bitmaps
• a bitmap is an array of numbers that represent
  the colors of individual dots on the screen
• data structures for bitmaps are more complex than
  those required for vector graphics
• there are several classes in GDI devoted to this
  purpose
• i.e., CachedBitmap stores a bitmap in memory for
  fast access and display

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typography

• the display of text in a variety of fonts, sizes,
  and styles
• GDI provides a lot of support for this complex
  task
• one of the new features in GDI is subpixel
  antialiasing
• gives text rendered on an LCD screen a smoother
  appearance

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the GDI class interface

• about 40 classes, 50 enumerations, and 6
  structures
• the Graphics class is the core of the GDI
  interface
• Its the class that actually draws lines, curves,
  figures, images, and text
• containers such as forms and panels pass these to
  their OnPaint() methods
• other classes work together with the Graphics
  class
• the GraphicsDrawLine method
• requires a Pen object
• holds attributes (color, width, dash style, and
  the like) of the line to be drawn
• the GraphicsFillRectangle method
• can use a LinearGradientBrush object
• to fill a rectangle with a gradually changing
  color
• Font and StringFormat objects influence the way a
  Graphics object draws text
• a Matrix object stores and manipulates the world
  transformation of a Graphics object
• used to rotate, scale, and flip images.

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the Graphics class

• provides methods for drawing lines, curves,
  figures, images, and text
• stores attributes of the display device and
  attributes of the items to be drawn
• encapsulates a GDI drawing surface and is
  associated with a specific device context
• How to get a Graphics object
• call the Control.CreateGraphics method on an
  object that inherits from System.Windows.Forms.Con
  trol
• handle a control's Control.Paint event and access
  the Graphics property of the System.Windows.Forms.
  PaintEventArgs class

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the GDI class interface

• some classes serve primarily as structured data
  types
• i.e., Rectangle, Point, and Size are for general
  purposes
• others are specialized and are considered helper
  classes
• i.e., the BitmapData class is a helper for the
  Bitmap class
• the PathData class is a helper for the
  GraphicsPath class
• GDI defines a few structures for organizing data
• i.e., the ColorMap structure holds a pair of
  Color objects that form one entry in a color
  conversion table.
• GDI defines several enumerations
• the LineJoin enumeration contains
• LineJoinBevel, LineJoinMiter, and LineJoinRound
• styles that can be used to join two lines

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sample programs and code snippets

• showdate
• gradient picker (and project 1)
• line drawing program
• ImageList control
• how to embed bitmaps
• PictureBox control
• drawing bitmaps directly in OnPaint()

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the end of this PowerPoint file
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