Visual Basic.NET How to Program (PDF)

746 Graphics and Multimedia Chapter 16
A graphics context represents a drawing surface on the screen. A Graphics object provides access
to the graphics context of a control.
An instance of the Pen class is used to draw lines.
An instance of one of the classes that derive from abstract class Brush is used to draw solid
shapes.
The Point structure can be used to represent a point in a two-dimensional plane.
Graphics objects contain methods for drawing, font manipulation, color manipulation and other
graphics-related actions.
Method OnPaint normally is called in response to an event, such as the uncovering of a window.
This method, in turn, triggers a Paint event.
Structure Color defines constants for manipulating colors in a Visual Basic program.
Color properties R, G and B return Integer values from 0 to 255, representing the amounts of
red, green and blue, respectively, that exist in a Color. The larger the value, the greater the
amount of that particular color.
Visual Basic provides class ColorDialog to display a dialog that allows users to select colors.
Component property BackColor (one of the many Component properties that can be called
on most GUI components) changes the component’s background color.
Class Font’s constructors all take at least three arguments—the font name, the font size and the
font style. The font name is any font currently supported by the system. The font style is a member
of the FontStyle enumeration.
Class FontMetrics defines several methods for obtaining font metrics.
Class Font provides the Bold, Italic, Strikeout and Underline properties, which return
True if the font is bold, italic, strikeout or underlined, respectively.
Class Font provides the Name property, which returns a String representing the name of the
font.
Class Font provides the Size and SizeInPoints properties, which return the size of the font
in design units and points, respectively.
The FontFamily class provides information about such font metrics as the family’s spacing and
height information.
The FontFamily class provides the GetCellAscent, GetCellDescent, GetEmHeight
and GetLineSpacing methods, which return the ascent of a font, descent of a font, the font’s
height in points and the distance between two consecutive lines of text, respectively.
Class Graphics provides methods DrawLine, DrawRectangle, DrawEllipse,
DrawArc, DrawLines, DrawPolygon and DrawPie, which draw lines and shape outlines.
Class Graphics provides methods FillRectangle, FillEllipse, FillPolygon and
FillPie, which draw solid shapes.
Classes HatchBrush, LinearGradientBrush, PathGradientBrush and Texture-
Brush all derive from class Brush and represent shape-filling styles.
Graphics method FromImage retrieves the Graphics object associated with the image file
that is its argument.
The DashStyle and DashCap enumerations define the style of dashes and their ends, respectively.
Class GraphicsPath represents a shape constructed from straight lines and curves.
GraphicsPath method AddLine appends a line to the shape that is encapsulated by the object.