Filters and alpha issue

[doskallemaskin]

Hi. I've been playing around with this wooonderful API and was doing a particlesystem. My next step was to try out filters.
 

Above is the filtered effect and below is the source. Don't get me wrong, it looks awesome! I just can't wrap my head around WHY all alpha channel is gone? It's regardless of what filter i use. (i've only tried pixi's internal ones so far). 

 

 

As you can see, the Bunny is changed as expected, but my particlesystem looks a bit wierd. 

All i do is this:

this.filter = new PIXI.PixelateFilter();this._currentCamera.filters = [this.filter];this.filter.size.x = 2;this.filter.size.y = 2;