The Three Parts of GDI+
The services of GDI+ fall into the following three broad categories:
- 2-D vector graphics
2-D Vector Graphics
Vector graphics involves drawing primitives (such as lines, curves, and figures) that are specified by sets of points on a coordinate system. For example, a straight line can be specified by its two endpoints, and 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 simple path can be specified by an array of points to be connected by straight lines. A Bézier spline is a sophisticated curve specified by four control points.
GDI+ provides classes (and structures) that store information about the primitives themselves, classes that store information about how the primitives are to be drawn, and classes that actually do the drawing. For example, the Rectangle structure stores the location and size of a rectangle; the Pen class stores information about line color, line width, and line style; and the Graphics class has methods for drawing lines, rectangles, paths, and other figures. There are also several Brush classes that store information about how closed figures and paths are to be filled with colors or patterns.
You can record a vector image (a sequence of graphics commands) in a metafile. GDI+ provides the Metafile class for recording, displaying, and saving metafiles. The MetafileHeader and MetaHeader classes allow you to inspect the data stored in a metafile header.
Certain kinds of pictures are difficult or impossible to display with the techniques of vector graphics. For example, the pictures on toolbar buttons and the pictures that appear as icons would be difficult to specify as collections of lines and curves. A high-resolution digital photograph of a crowded baseball stadium would be even more difficult to create with vector techniques. Images of this type are stored as bitmaps, arrays of numbers that represent the colors of individual dots on the screen. GDI+ provides the Bitmap class for displaying, manipulating, and saving bitmaps.
Typography is concerned with the display of text in a variety of fonts, sizes, and styles. GDI+ provides an impressive amount of support for this complex task. One of the new features in GDI+ is subpixel antialiasing, which gives text rendered on an LCD screen a smoother appearance.