CODEWITHSUNDEEP
actionscript-3
thedayturns
thedayturns

Reputation: 10823

Why isn't the BitmapData transparent?

    var subimage = new Bitmap();
    subimage.bitmapData = new BitmapData(25, 25, true, 0);
    addChild(subimage);

From everything I've read, this should be transparent. I'm seeing a big black square. What could cause that?

Upvotes: 7

Views: 4717

Answers (4)

Chunky Chunk
Chunky Chunk

Reputation: 17217

You can either create or pass BitmapData to the constructor of a new Bitmap object, or edit it by reference after it is created. Both options work:

package 
{
    //Imports
    import flash.display.Bitmap;
    import flash.display.BitmapData;
    import flash.display.Sprite;

    //Document Class
    public class Main extends Sprite 
    {
        //Constructor
        public function Main() 
        {
            var bmpData:BitmapData = new BitmapData(200, 200, true, 0x5500FF00);
            var bmp:Bitmap = new Bitmap(bmpData);

            addChild(bmp);

            var bmp2:Bitmap = new Bitmap();
            bmp2.bitmapData = new BitmapData(200, 200, true, 0x55FF0000);
            bmp2.x = bmp2.y = 200;

            addChild(bmp2);
        }
    }
}

Upvotes: 3

sanchez
sanchez

Reputation: 4530

use this 

new BitmapData(25, 25, true, 0x00000000);

instead of 

new BitmapData(25, 25, true, 0);

0xFF000000 is black(0x000000) with alpha equal to 1

0x00000000 is black(0x000000) with alpha equal to 0

Here is a nice explanation how colors & alpha work: http://myflex.wordpress.com/2007/09/07/about-hex-color-codes-in-flex-as3/

//EDIT:

Dennis Krøger and strille are right, 0x00000000 == 0. Looks like the problem is somewhere else, not in the code you pasted in.

Upvotes: 13

DennisK
DennisK

Reputation: 416

It makes no sense: I tried the following code:

package
{
    import flash.display.Bitmap;
    import flash.display.BitmapData;
    import flash.display.Sprite;

public class TestBitMap extends Sprite
    {
        public function TestBitMap() {
            var imageYellow:Bitmap = new Bitmap(new BitmapData(100, 100, true, 0xFFFFFF00));
            var imageTransparent:Bitmap = new Bitmap(new BitmapData(100, 100, true, 0));
            var imageSemiTransparent:Bitmap = new Bitmap(new BitmapData(100, 100, true, 0x99000000));
            imageTransparent.x = 25;
            imageTransparent.y = 25;
            imageSemiTransparent.x = 50;
            imageSemiTransparent.y = 50;
            addChild(imageYellow);
            addChild(imageTransparent);
            addChild(imageSemiTransparent);
        }       
    }
}

And I got a yellow box with a semitransparent black box over it. The "imageTransparent" was completely invisible.

I also tried your method with creating the BitMap first, then changing the bitmapData. No difference, still invisible.

San.chez: 0 is equal to 0x00000000, no matter what. It is an unsigned integer, ActionScript doesn't magically change it. Your link is good though.

Upvotes: 2

raju-bitter
raju-bitter

Reputation: 8996

ActionScript uses a 32-bit hexadecimal numbers to represent color values with transparency. ARGB colors as 32 bit variables are specified by 4 groups of 8 bits each / or 2 hex each:

In binary: AAAAAAAA RRRRRRRR GGGGGGGG BBBBBBBB

In hex: AA RR GG BB

A represents the alpha value (transparency), R is rd, G is green, B is blue. Each group defines intensity of each of the colors channels, A is alpha, R is red, G is green, B is blue. Full intensity on the alpha channel means no alpha (FF) and no intensity (00) means full alpha. So a transparent pixel color value is 0x00rrggbb.

Upvotes: 3

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