|
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
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).
-
Point
-
A single location in a coordinate space. In the 2-d coordinate
system used in ActionScript, a point is defined by its location
along the x axis and the y axis (the point’s coordinates).
-
Quadratic Bézier curve
-
A type of curve defined by a particular mathematical formula.
In this type of curve, the shape of the curve is calculated based
on the positions of the anchor points (the end points of the curve)
and a control point that defines the amount and direction of the
curve.
-
Scale
-
The size of an object relative to its original size. When
used as a verb, to scale an object means to change its size by stretching
or shrinking the object.
-
Stroke
-
The outline portion of a shape that has a line filled in
with color, or the lines of an un-filled shape.
-
Translate
-
To change a point’s coordinates from one coordinate space
to another.
-
X axis
-
The horizontal axis in the 2-d coordinate system used in
ActionScript.
-
Y axis
-
The vertical axis in the 2-d coordinate system used in ActionScript.
|
|
|
