Visual Basic® 2008 Programmer's Reference

Chapter 33. Image Processing

The Graphics class represents a drawing surface at a logical level. Below that level, a Graphics object is attached to a Bitmap or Metafile object. Those objects understand the slightly lower-level needs of managing more physical data structures. For example, a Bitmap object maps abstract drawing commands such as DrawLine and DrawEllipse to colored pixels that can be displayed on a PictureBox or saved into a file. Similarly, a Metafile maps the Graphics object's abstract commands into metafile records that you can play back on a drawing surface, or save in a graphical metafile.

This chapter describes the more down-to-earth Bitmap and Metafile classes. It explains methods for building, modifying, and manipulating these objects. It shows how to load and save them from graphics files and, in the case of Bitmap classes, how to work with files saved in a variety of graphic formats such as BMP, GIF, JPEG, TIFF, and PNG.

Image

An Image object represents some sort of picture that you can draw on, copy, transform, and display. Image is an abstract (MustInherit) class, so you cannot create instances of this class directly. Instead you must make instances of its derived classes Bitmap and Metafile.

You can also derive your own class from Image if you want, although that's a fairly advanced technique, so it isn't covered here.

The Image class provides useful graphical methods that the Bitmap and Metafile classes inherit. Many other objects can work with any type of ...