You can measure and manipulate the
size of a display object in two ways, using either the dimension
properties (width and height)
or the scale properties (scaleX and scaleY).
Every display object has a width property and
a height property, which are initially set to the
size of the object in pixels. You can read the values of those properties
to measure the size of the display object. You can also specify
new values to change the size of the object, as follows:
// Resize a display object.
square.width = 420;
square.height = 420;
// Determine the radius of a circle display object.
var radius:Number = circle.width / 2;
Changing the height or width of
a display object causes the object to scale, meaning its contents
stretch or squeeze to fit in the new area. If the display object contains
only vector shapes, those shapes will be redrawn at the new scale,
with no loss in quality. Any bitmap graphic elements in the display
object will be scaled rather than redrawn. So, for example, a digital
photo whose width and height are increased beyond the actual dimensions
of the pixel information in the image will be pixelated, making
it look jagged.
When you change the width or height properties
of a display object, Flash Player and AIR update the scaleX and scaleY properties
of the object as well.
Note: TextField objects are an exception to this scaling behavior.
Text fields need to resize themselves to accommodate text wrapping
and font sizes, so they reset their scaleX or scaleY values to 1
after resizing. However, if you adjust the scaleX or scaleY values
of a TextField object, the width and height values change to accommodate
the scaling values you provide.
These properties represent the relative size of the display object
compared to its original size. The scaleX and scaleY properties
use fraction (decimal) values to represent percentage. For example,
if a display object’s width has been changed so
that it’s half as wide as its original size, the object’s scaleX property will
have the value .5, meaning 50 percent. If its height
has been doubled, its scaleY property will have
the value 2, meaning 200 percent.
// circle is a display object whose width and height are 150 pixels.
// At original size, scaleX and scaleY are 1 (100%).
trace(circle.scaleX); // output: 1
trace(circle.scaleY); // output: 1
// When you change the width and height properties,
// Flash Player changes the scaleX and scaleY properties accordingly.
circle.width = 100;
circle.height = 75;
trace(circle.scaleX); // output: 0.6622516556291391
trace(circle.scaleY); // output: 0.4966887417218543
Size changes are not proportional. In other words, if you change
the height of a square but not its width,
its proportions will no longer be the same, and it will be a rectangle
instead of a square. If you want to make relative changes to the size
of a display object, you can set the values of the scaleX and scaleY properties
to resize the object, as an alternative to setting the width or height properties.
For example, this code changes the width of the
display object named square, and then alters the
vertical scale (scaleY) to match the horizontal
scale, so that the size of the square stays proportional.
// Change the width directly.
square.width = 150;
// Change the vertical scale to match the horizontal scale,
// to keep the size proportional.
square.scaleY = square.scaleX;