Here is the example:
var shader:Shader = new Shader( new myshader() as ByteArray);
var bmp:Bitmap = new image1() as Bitmap;
var bmp2:Bitmap = new image2() as Bitmap;

var bmpdata:BitmapData = new BitmapData(256,256,true);
bmpdata.draw(bmp);
var bmp3:Bitmap = new Bitmap(bmpdata);

bmp3.blendShader = shader;
bmp3.blendMode = BlendMode.SHADER;

this.addChild(bmp2);
this.addChild(bmp3);