GDI provides abstraction for graphics hardware by allowing calls to Windows API graphics functions without needing to know specifics of the video card. It uses device contexts (DCs) as the main object for drawing. GDI+ builds on GDI by providing a more intuitive object-oriented interface and some performance improvements. The .NET Framework encapsulates GDI+ functionality in the System.Drawing namespace for 2D graphics like drawing lines, shapes, and text without 3D capabilities. Key classes include Graphics for drawing and Pen, Brush, and Image for defining drawing objects. Alpha blending and blending are used for transparency effects and gradients in drawings.

1. GDI

2. • GDI provides a layer of abstraction, hiding the
differences between the different video cards.
You simply call the Windows API function to
do the specific task, and internally the GDI
figures out how to get your particular video
card to do whatever it is you want.
• the device-context object (DC) is a very
powerful object and you won’t be surprised to
learn that under GDI all drawing had to be
done through a device context.

3. • GDI+ to a large extent sits as a layer between
GDI and your application, providing a more
intuitive, inheritance-based object model.
• Although GDI+ is basically a wrapper around
GDI, Microsoft has been able through GDI+ to
provide new features and claims to have
made some performance improvements.

4. • System.Drawing namespace that encapsulates .NET’s
basic graphics functionality, which is known as GDI+.
• The name GDI+ comes from the original Windows graphics
library, which was called the Graphical Device Interface.
• It is a library of simple 2D graphics designed to draw lines
and shapes, draw text, and display bitmaps. There is no
3D functionality in any of GDI+.
• If you need 3D graphics, you are going to have to consider
using Direct3D.

5. GDI+ namespaces
• System.Drawing :-Contains most of the
classes, structs, enums, and delegates concerned with the basic functionality of drawing
• System.Drawing.Drawing2D:- Provides most
of the support for advanced 2D and vector
drawing, including anti-aliasing, geometric
transformations, and graphics paths
• System.Drawing.Imaging:- Contains various
classes that assist in the manipulation of
images (bitmaps, GIF files, and so on)

6. classes
• the .NET base class System.Drawing.Graphics .
Most drawing is done by calling methods on an
instance of Graphics .
• In fact, since the Graphics class is the class that
is responsible for handling most drawing
operations,
• Form1, derived from System.Windows.Form,
which represents the application’s main
window.
• System.Drawing.Pen : A Pen is one of a number
of supporting objects to help with drawing

7. • PaintEventArgs is a class that is derived from
the EventArgs class normally used to pass in
informa-tion about events.
• Region is a class that represents an area of the
screen that has some complex shape. the
process of initializing a Region instance is itself
quite complex.
• the Control class, from which both Form and
all the various Windows Forms controls
derive, that maintains the information needed
to carry out the conversion.

8. blending and alpha blending
• Alpha blending is the process of creating a Pen,
Brush, or Image that has attributes that
determine its transparency.
• Blending is the process of drawing a line or filling
a shape with a color that starts out at one end of
the spectrum (range) and ends at the other.
• An example of alpha blending would be creating
an image on the screen.
• An example of blending would be drawing an
ellipse that is filled starting with blue and ending
with red

9. The top one is the gamma correction for the top image
and the bottom one is the alpha blend for the line.

10. GDI+
• Alpha blending allows two objects to be visually
blended(merge) together. This is primarily used
for 3D atmospheric and environmental effects.
• It allows such things as "fogging", where an
image is rendered behind another translucent
(clear) image, which creates the effect of looking
though fog or looking down through a pool and
seeing the bottom. It also allows Depth Cueing,
which is the lowering of the intensity of lighting
to make an object appear farther away.