actionscript-3 – 在flash AS3中使用BlendMode“erase”时的奇

这是一个例子.我在舞台上绘制了一个黑色背景,然后将2个重叠的圆圈绘制成一个精灵,并尝试从背景中删除它们.

var solidBitmapData = new BitmapData(550,400,true,0x000000);
            var mySpriteLayer = new Sprite();

            // Create black background.
            mySpriteLayer.graphics.beginFill(0x000000);
            mySpriteLayer.graphics.drawRect(0,550,400);
            mySpriteLayer.graphics.endFill();

            // Draw it to bitmap data.
            solidBitmapData.draw(mySpriteLayer);

            // Clear sprite.
            mySpriteLayer.graphics.clear();

            // Draw two circles
            mySpriteLayer.graphics.beginFill(0xFF0000);
            mySpriteLayer.graphics.drawCircle(200,200,50);
            mySpriteLayer.graphics.endFill();
            mySpriteLayer.graphics.beginFill(0xFF0000);
            mySpriteLayer.graphics.drawCircle(250,50);
            mySpriteLayer.graphics.endFill();

            // Draw circles to bitmap with blend mode erase.
            solidBitmapData.draw(mySpriteLayer,null,BlendMode.ERASE);

            // Create bitmap and add to stage.
            var solidBitmap = new Bitmap(solidBitmapData);
            addChild(solidBitmap);

我在谈论圈子中间的线条.这似乎与linestyle有关但我已经尝试将其设置为零并将alpha设置为0但我无法摆脱线条.

有任何想法吗？