Bug when using BitmapData.draw() with blend-modes

Question

I want to fill bitmapdata with transparent sprites using different transformations and blend-modes. It causes light lines on the borders of image after drawing.

Here is screenshot of result without using blend-modes http://www.flasher.ru/forum/attachment.php?attachmentid=30347&stc=1&d=1389390901 And result when using blend-modes http://www.flasher.ru/forum/attachment.php?attachmentid=30348&stc=1&d=1389390901

here example of code, as singleSp you can use any transparent image

    package 
    {
import flash.display.Bitmap;
import flash.display.BitmapData;
import flash.display.Sprite;
import flash.geom.ColorTransform;
import flash.geom.Matrix;
import flash.geom.Rectangle;
import flash.display.StageScaleMode;
import flash.display.StageAlign;

public class Main extends Sprite 
{

    [Embed(source = "assets/pic1.png")]
    public var singleSp:Class;

    var picBD:BitmapData;
    var picBM:Bitmap;


    public function Main():void 
    {
        picBD = new BitmapData(600, 600, true, 0);
        picBM = new Bitmap(picBD, "auto", true);
        addChild(picBM);

        var tr:Matrix = new Matrix();

        var drawIm:BitmapData = (new singleSp as Bitmap).bitmapData;

        for (var i:int = 0; i < 30; i++ ) {

            var scale:Number = 0.3 + Math.random() * 0.8;               
            tr.setTo(1, 0, 0, 1, 0, 0);
            tr.scale(scale, scale);
            tr.rotate(Math.random() * 2);
            tr.tx = Math.random() * 150 + 150;
            tr.ty = Math.random() * 150;                

            picBD.draw(drawIm, tr, new ColorTransform(1,1,1,0.4), "invert", null, true);

        }
    }       
}

}

Answer 1

I have run a test and I can seen those lines (edges of the image) My guess is that artefact is due to the semi transparent colorTransform.