The Graphics Class

Mahesh Chand
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This article has been excerpted from book "Graphics Programming with GDI+ ".

Graphics objects are the heart of GDI+. They are represented by the Graphics class, which defines methods and properties to draw and fill graphics objects. Whenever an application needs to draw or paint something, it has to use the Graphics object. Hence, understanding the Graphics class, its methods, and its properties is very important.

Specifically, in this article we will discuss the methods and properties of the Graphics class, and how to use them in real-world applications, including line charts, pie charts, and our GDI+Painter application. GDI+Painter is similar to the PaintBrush application, which allows you to draw simple graphics object such as lines, rectangles, and circles and save the images as bitmaps.

Graphics Class Properties

The Graphics class provides a long list of properties (see Table 3.1) and methods.

TABLE 3.1: Graphics properties

Property	Description
Clip	Gets and sets a Region type that limits the drawing region of the Graphics object.
ClipBounds	Returns a RectangeF structure that bounds the clipping region of this Graphics object. Supports read only access.
CompositingMode	Returns a value of type CompositingMode enumeration representing how composite images are drawn to the Graphics object.
CompositingQuality	Gets and sets the rendering quality (directly proportional to the visual quality of the output and inversely proportional to the rendering time) of composite images, represented by the CompositingQuality enumeration.
DpiX	Returns the horizontal resolution (dots per inch) of a Graphics object.
DpiY	Returns the vertical resolution (dots per inch) of a Graphics object.
InterpolationMode	Gets and sets the interpolation mode (which determines intermediate values between two endpoints), represented by the InterpolationMode enumerator.
IsClipEmpty	Returns a value indicating whether the clipping region of a Graphics object is empty. When there is no clipping this property return false.
IsVisibleClipEmpty	Returns a value indicating whether the visible clipping region of a Graphics object is empty.
PageScale	Gets and sets a value for scaling between world units and page units for this Graphics object.
PageUnit	Gets and sets a value that represents the unit of measure for page coordinates.
PixelOffsetMode	Gets and sets a value for the pixel offset mode (PixelOffsetMode enumeration).
RenderingOrigin	Represents the rendering origin of a Graphics object for dithering and hatch brushes.
SmoothingMode	Gets and sets the smoothing mode of a Graphics object (SmoothingMode enumeration). Does not affect text. Smoothing modes include high quality, high speed, and anti-aliasing.
TextContrast	Gets and sets the gamma correction value for rendering anti-aliased and ClearType text values, ranging from 0 to 12. The default is 4.
TextRenderingHint	Gets and sets the text rendering quality (TextRenderingHint enumeration). Affects only text drawn on the Graphics object.
Transform	Gets and sets the world transformation matrix (transformation is the process of converting graphics objects from one state to another). The transformation state is represented by a transformation matrix.
VisibleClipBounds	Gets and sets the visible clipping region of the Graphics object (the intersection of the clipping region of the Graphics object and the clipping region of the window).

Graphics Class Methods

We can divide Graphics class methods into three categories: draw, fill, and miscellaneous. Draw methods are used to draw lines, curves, and outer boundaries of closed curves and images. Fill methods fill the interior area of graphics objects. There are also a few miscellaneous methods that fall in neither category-for example, MeasureString and Clear.

Draw Methods

The draw methods of the Graphics class are used to draw lines, curves, and outer boundaries of closed curves and images. Table 3.2 lists the draw methods of the Graphics class.

TABLE 3.2: Graphics draw methods

Mehtods	Description
DrawArc	Draws an arc (a portions of an ellipse specified by a pair of coordinates, a width, a height, and start and end angles).
DrawBezier	Draws a Bezier curve defined by four Point structures.
DrawBeziers	Draws a series of Bezier splines from an array of Point structures.
DrawClosedCurve	Draws a closed cardinal spline defined by an array of Point structures.
DrawCurve	Draws a cardinal spline through a specified array of Point structures.
DrawEllipse	Draws an ellipse defined by a bounding rectangle specified by a pair of coordinates, a height, and a width.
DrawIcon	Draws an image represented by the specified Icon object at the specified coordinates.
DrawIconUnstretched	Draws an image represented by the specified Icon object without scaling the image.
DrawImage	Draws the specified Image object at the specified location and with the original size.
DrawImageUnscaled	Draws the specified Image object with its original size at the location specified by a coordinate pair.
DrawLine	Draws a line connecting two points specified by coordinate pairs.
DrawLines	Draws a series of line segments that connect an array of Point structures.
DrawPath	Draws a GraphicsPath object.
DrawPie	Draws a pie shape specified by a coordinate pair, a width, a height, and two radial lines.
DrawPolygon	Draws a polygon defined by an array of Point structures.
DrawRectangle	Draws a rectangle specified by a coordinate pair, a width, and a height.
DrawRectangles	Draws a series of rectangles specified by an array of Rectangle structures.
DrawString	Draws the specified text string at the specified location using the specified Brush and Font objects.

Conclusion

Hope the article would have helped you in understanding Graphic Class methods and properties. Read other articles on GDI+ on the website.

This book teaches .NET developers how to work with GDI+ as they develop applications that include graphics, or that interact with monitors or printers. It begins by explaining the difference between GDI and GDI+, and covering the basic concepts of graphics programming in Windows.

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