Recipe 8.1.
Creating a BitmapData Object
Problem
You want to create a new bitmap in your
application.
Solution
Use the BitmapData class's constructor to
create a new BitmapData object.
Discussion
The BitmapData class represents the
pixels in a bitmap image, and contains many built-in methods for
adding content to and manipulating that image. The first step is to
create an instance of the class by calling its constructor, as
follows:
var bitmap:BitmapData = new BitmapData(width, height,
transparent, fillColor);
This class is part of the flash.display package, so make
sure you import flash.display.BitmapData at the top of the
file. The width and height parameters specify
what size bitmap you want to create. The next parameter is a
Boolean value, which specifies whether the bitmap is created with
an alpha channel (true) or not
(false), and the fillColor determines the initial
background color of the image.
Although width and
height are mandatory, transparent
and fillColor default to true and
0xFFFFFFFF, respectively if not explicitly passed to the
constructor.
The fillColor accepts a 32-bit color value, which means that
it supports an alpha channel. Of course, the alpha channel of the
fill color is only relevant if you create the BitmapData
specifying transparent as true. Otherwise, all
colors are treated as 100 percent opaque.
The following example creates a
BitmapData that is initially completely transparent, as the
alpha channel of the fillColor is set to zero:
var bitmap:BitmapData = new BitmapData(100, 100,
true, 0x00FFFFFF);
After you create a new BitmapData, it
exists only in memory. Although you can create content in the image
and manipulate it, it will not be visible until you add it to the
display list.
See Also
Recipe
8.2 for information on how to make a BitmapData
visible.
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