I have a performance question about pixel bender. I want to enlarge many BitmapData (double their size into new BitmapData). I was doing this with as3, but wanted to use pixel bender to get better performance. On my machines, I get great comparative performance out of many pixel bender demonstrations.

To my surprise (or bad coding / understanding), I am getting much worse performance out of pixel bender -- 2 seconds to do 3000 scalings vs .5 seconds! I expected to get at least the same performance as as3. What am I doing wrong?

I got the straightforward pixel bender code here (and it is included below for easy reference).

package
{

import aCore.aUtil.timingUtils;

import flash.display.BitmapData;
import flash.display.Shader;
import flash.display.ShaderJob;
import flash.display.Sprite;
import flash.display.StageAlign;
import flash.display.StageScaleMode;
import flash.events.Event;
import flash.geom.Matrix;

public class flashFlash extends Sprite
{


[Embed ( source="pixelbender/bilinearresample.pbj", mimeType="application/octet-stream" ) ]
private static var BilinearScaling:Class;

public function flashFlash( ):void
{
    stage.align = StageAlign.TOP_LEFT;
    stage.scaleMode = StageScaleMode.NO_SCALE;

    addEventListener( Event.ENTER_FRAME, efCb, false, 0, true );
}

private function efCb( evt:Event ):void
{
    removeEventListener( Event.ENTER_FRAME, efCb, false );

    traceTime( "init" );

    var srcBmd:BitmapData = new BitmapData( 80, 120, false, 0 );
    var destBmd:BitmapData = new BitmapData( 160, 240, false, 0 );

    var mx:Matrix = new Matrix( );
    mx.scale( 2, 2 );
    for (var i:uint = 0; i < 3000; i++)
    {   destBmd.draw( srcBmd, mx );
    }

    traceTime( "scaled with as3" );

    // create and configure a Shader object
    var shader:Shader = new Shader( );
    shader.byteCode = new BilinearScaling( );
    shader.data.scale.value = [2];
    shader.data.src.input = srcBmd;

    for (var j:uint = 0; j < 3000; j++)
    {
        var shaderJob:ShaderJob = new ShaderJob( );
        shaderJob.shader = shader;
        shaderJob.target = destBmd;
        shaderJob.start( true );
    }

    traceTime( "scaled with pixel bender bilinearresample.pbj" );
}

private static var _lastTraceTime:Number = new Date().getTime();
public static function traceTime( note:String ):Number
{   var nowTime:Number = new Date().getTime();
    var diff:Number = (nowTime-_lastTraceTime);
    trace( "[t" + diff + "] " + note );
    _lastTraceTime = nowTime;
    return diff;
}

}
}

And the pixel bender code:

<languageVersion : 1.0;>

kernel BilinearResample
<   namespace : "com.brooksandrus.pixelbender";
    vendor : "Brooks Andrus";
    version : 1;
    description : "Resizes an image using bilinear resampling. Constrains aspect ratio - divide Math.max( input.width / output.width, input.height / output.height ) and pass in to the scale parameter";
>
{
    parameter float scale
    <
        minValue: 0.0;
        maxValue: 1000.0;
        defaultValue: 1.0;
    >;

    input image4 src;
    output pixel4 dst;

    void
    evaluatePixel()
    {
        // scale should be Math.max( src.width / output.width, src.height / output.height )
        dst = sampleLinear( src, outCoord() * scale ); // bilinear scaling
    }
}