ACTIONSCRIPT 3 Developer’s Guide en

Chapter 12: Using the drawing API
Flash Player 9 and later, Adobe AIR 1.0 and later
Although imported images and artwork are important, the functionality known as the drawing API, which allows you
to draw lines and shapes in ActionScript, gives you the freedom to start an application with the computer equivalent
of a blank canvas, on which you can create whatever images you wish. The ability to create your own graphics opens
up broad possibilities for your applications. With the techniques covered here you can create a drawing program, make
animated, interactive art, or programmatically create your own user interface elements, among many possibilities.
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flash.display.Graphics
Basics of the drawing API
Flash Player 9 and later, Adobe AIR 1.0 and later
The drawing API is the name for the functionality built into ActionScript that allows you to create vector graphics—
lines, curves, shapes, fills, and gradients—and display them on the screen using ActionScript. The
flash.display.Graphics class provides this functionality. You can draw with ActionScript on any Shape, Sprite, or
MovieClip instance, using the graphics property defined in each of those classes. (Each of those classes’ graphics
property is in fact an instance of the Graphics class.)
If you’re just getting started with drawing with code, the Graphics class includes several methods that make it easy to
draw common shapes like circles, ellipses, rectangles, and rectangles with rounded corners. You can draw them as
empty lines or filled shapes. When you need more advanced functionality, the Graphics class also includes methods
for drawing lines and quadratic Bézier curves, which you can use in conjunction with the trigonometry functions in
the Math class to create any shape you need.
Flash runtimes (such as Flash Player 10 and Adobe AIR 1.5 and later versions) add an additional API for drawing,
which allow you to programmatically draw entire shapes with a single command. Once you’re familiar with the
Graphics class and tasks covered in “Basics of using the drawing API”, continue to “Advanced use of the drawing API”
on page 234 to learn more about these drawing API features.
Important concepts and terms
The following reference list contains important terms that you will encounter while using the drawing API:
Anchor point One of the two end points of a quadratic Bézier curve.
Control point The point that defines the direction and amount of curve of a quadratic Bézier curve. The curved line
never reaches the control point; however, the line curves as though being drawn toward the control point.
Coordinate space The graph of coordinates contained in a display object, on which its child elements are positioned.
Fill The solid inner portion of a shape that has a line filled in with color, or all of a shape that has no outline.
Gradient A color that consists of a gradual transition from one color to one or more other colors (as opposed to a solid
color).
Last updated 6/6/2012
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