XNA - DXT5 Normal Map Content Processor

[ContentProcessor( DisplayName = "Texture - DXT Normal Map" )]
public class DxtNormalMapProcessor : TextureProcessor {

    // PUBLIC DATA

    // Hard-coded parameter values - optional:

    public override bool GenerateMipmaps {
        get { return true; }
        set { }
    }

    public override bool ColorKeyEnabled {
        get { return false; }
        set { }
    }

    public override bool PremultiplyAlpha {
        get { return false; }
        set { }
    }

    public override TextureProcessorOutputFormat TextureFormat {
        get { return TextureProcessorOutputFormat.DxtCompressed; }
        set { }
    }



    // PUBLIC METHODS

    /// <summary>
    /// Processes the texture for DXT5 normal map compression. Moves X to green and Y to alpha.
    /// </summary>
    public override TextureContent Process( TextureContent input, ContentProcessorContext context ) {

        // Move X to green and Y to alpha
        foreach ( MipmapChain face in input.Faces ) {
            foreach ( BitmapContent bitmap in face ) {
                byte[] data = bitmap.GetPixelData();
                for ( int i = 0; i < data.Length; i += 4 ) {
                    int red = i, green = i + 1, blue = i + 2, alpha = i + 3;
                    data[ alpha ] = data[ green ];
                    data[ green ] = data[ red ];
                    data[ red ] = 0;
                    data[ blue ] = 0;
                }
                bitmap.SetPixelData( data );
            }
        }

        // Do base class processing
        TextureContent output = base.Process( input, context );

        // Return result
        return output;
    }

} // end class