The revised ColorOffsetFilter of the tutorial from the Starling manual; now with fixed PMA handling.

ColorOffsetFilter.as

// =================================================================================================
//
//	Starling Framework
//	Copyright Gamua GmbH. All Rights Reserved.
//
//	This program is free software. You can redistribute and/or modify it
//	in accordance with the terms of the accompanying license agreement.
//
// =================================================================================================

package starling.extensions
{
    import starling.filters.FragmentFilter;
    import starling.rendering.FilterEffect;

    public class ColorOffsetFilter extends FragmentFilter
    {
        public function ColorOffsetFilter(redOffset:Number=0, greenOffset:Number=0,
                                          blueOffset:Number=0, alphaOffset:Number=0):void
        {
            colorOffsetEffect.redOffset = redOffset;
            colorOffsetEffect.greenOffset = greenOffset;
            colorOffsetEffect.blueOffset = blueOffset;
            colorOffsetEffect.alphaOffset = alphaOffset;
        }

        override protected function createEffect():FilterEffect
        {
            return new ColorOffsetEffect();
        }

        private function get colorOffsetEffect():ColorOffsetEffect
        {
            return effect as ColorOffsetEffect;
        }

        public function get redOffset():Number { return colorOffsetEffect.redOffset; }
        public function set redOffset(value:Number):void
        {
            colorOffsetEffect.redOffset = value;
            setRequiresRedraw();
        }

        public function get greenOffset():Number { return colorOffsetEffect.greenOffset; }
        public function set greenOffset(value:Number):void
        {
            colorOffsetEffect.greenOffset = value;
            setRequiresRedraw();
        }

        public function get blueOffset():Number { return colorOffsetEffect.blueOffset; }
        public function set blueOffset(value:Number):void
        {
            colorOffsetEffect.blueOffset = value;
            setRequiresRedraw();
        }

        public function get alphaOffset():Number { return colorOffsetEffect.alphaOffset; }
        public function set alphaOffset(value:Number):void
        {
            colorOffsetEffect.alphaOffset = value;
            setRequiresRedraw();
        }
    }
}

import flash.display3D.Context3D;
import flash.display3D.Context3DProgramType;

import starling.rendering.FilterEffect;
import starling.rendering.Program;

class ColorOffsetEffect extends FilterEffect
{
    private var _offsets:Vector.<Number>;

    private static const MIN_COLOR:Vector.<Number> = new <Number>[0, 0, 0, 0.001];

    public function ColorOffsetEffect()
    {
        _offsets = new Vector.<Number>(4, true);
    }

    override protected function createProgram():Program
    {
        var vertexShader:String = STD_VERTEX_SHADER;
        var fragmentShader:String = [
            tex("ft0", "v0", 0, texture),     // get color from texture
            "mov ft1, fc0",                   // copy complete offset to ft1
            "mul ft1.xyz, fc0.xyz, ft0.www",  // multiply offset.rgb with alpha (pma!)
            "add  oc, ft0, ft1     "          // add offset, copy to output
        ].join("\n");

        return Program.fromSource(vertexShader, fragmentShader);
    }

    override protected function beforeDraw(context:Context3D):void
    {
        context.setProgramConstantsFromVector(Context3DProgramType.FRAGMENT, 0, _offsets);
        context.setProgramConstantsFromVector(Context3DProgramType.FRAGMENT, 1, MIN_COLOR);
        super.beforeDraw(context);
    }

    public function get redOffset():Number { return _offsets[0]; }
    public function set redOffset(value:Number):void { _offsets[0] = value; }

    public function get greenOffset():Number { return _offsets[1]; }
    public function set greenOffset(value:Number):void { _offsets[1] = value; }

    public function get blueOffset():Number { return _offsets[2]; }
    public function set blueOffset(value:Number):void { _offsets[2] = value; }

    public function get alphaOffset():Number { return _offsets[3]; }
    public function set alphaOffset(value:Number):void { _offsets[3] = value; }
}