/**
 * update an image by altering the pixels to become grayscale.
 */
void irr::output::CScreenFilter::modifyGrayscale(video::ITexture* image)
{
	irr::c8* data;
	irr::s32 code;
	irr::u32 steps;
	IplImage* modify;
	IplImage* modified;
	core::dimension2di size;

	// retrieve the size of the image
	size = image->getSize();

	// retrieve the specific code to use for formatting and the number of steps
	switch( image->getColorFormat() )
	{
	default: // unknown
	case video::ECF_R8G8B8:		steps = 3; code = CV_RGB2GRAY;	break; // RGB
	case video::ECF_A8R8G8B8:	steps = 4; code = CV_RGBA2GRAY;	break; // ARGB
	}

	// retrieve the data pointer object for transformation on the image
	data = (char*)image->lock();

	// create the image using openCV
	modify = cvCreateImageHeader( cvSize(size.Width, size.Height), IPL_DEPTH_8U, 1 );
	modified = cvCreateImageHeader( cvSize(size.Width, size.Height), IPL_DEPTH_8U, 1 );

	// copy the data from the original texture into the new image object
	cvSetData( modify, data, size.Width * steps );

	// perform the grayscale operation on the data
	cvCvtColor( modify, modified, code );

	// ensure that the data is updated to match the grayscale image
	memcpy( data, modified->imageData, modified->imageSize );

	// destroy the image since it is no longer required
	cvReleaseImageHeader( &modify );
	cvReleaseImageHeader( &modified );

	// unlock the image for processing normally by the irrlicht engine
	image->unlock();
}