=========for bitmapdata it self================

The alpha channel can used to store no zero value.            setPixel32  then  getPixel32  will match

If the alpha channel is 0 , it will set all the rgb balue to 0.     getPixel32()==0

=========when it upload to gpu over stage3d=========================

it will send the value after mutiply

bd.setPixel32(0, 0, 0xARGB);

the real value fetch by shader is this:  A   A/255*R    A/255*G    A/255*B

for example :  i want a value argb value such as (0.5,1,1,1) in the shader

then i do this bd.setPixel32(0, 0, 0x7fffffff);

the real value fetch by shader is this:  (0.5 0.5 0.5 0.5)

========================================================

There are there kinds value

val1=the parameter of setPixel32        

val2=the return value of getPixel32

val3=the texture value read by shader

if(alpha!=0)  val1==val2

if(alpha==0) val1!=val2   and  val2==0

val3=(val1.a , val1.a/255*val1.r, val1.a/255*val1.r, val1.a/255*val1.r)/255

Am i clear?

=============================================================

package 

{

    import flash.display.BitmapData;

    import flash.display.Sprite;

    public class BitmapDataTest extends Sprite

    {

        public function BitmapDataTest()

        {

            var bd:BitmapData = new BitmapData(128, 128);

            bd.setPixel32(0, 0, 0xffffffff);

            var storeValue:uint = bd.getPixel32(0, 0);

            trace(storeValue);//ok  and  also ok for shader

            bd.setPixel32(0, 0, 0x1ffffff);

            storeValue = bd.getPixel32(0, 0);

            trace(storeValue);//ok for bitmapdata but not ok for shader

            bd.setPixel32(0, 0, 0x0ffffff);

            storeValue = bd.getPixel32(0, 0);

            trace(storeValue);// not 0xffffff but 0

        }

    }

}