scale_mask_centered.groovy

#@Dataset(label="Image to transform") img
#@Double(label="scale") scaling_factor
#@UIService ui

import net.imglib2.*;
import net.imglib2.realtransform.*;
import net.imglib2.view.*;
import net.imglib2.interpolation.*;
import net.imglib2.interpolation.randomaccess.*;


int nd = img.numDimensions();
RealPoint p = new RealPoint(nd);
long N = 0;

c = img.cursor();
while( c.hasNext())
{
	if ( c.next().getRealDouble() > 0 )
	{
		N++;
		for( int i = 0; i < nd; i++ )
			p.setPosition( p.getDoublePosition( i ) + c.getDoublePosition( i ), i );
	}
}

for( int i = 0; i < nd; i++ )
	p.setPosition( p.getDoublePosition( i ) / N, i );

center = new double[ nd ];
p.localize( center );

t = new AffineTransform3D();  // centering part
t.translate( center );

transform = new AffineTransform3D();
transform.preConcatenate( t.inverse() );  	// center about zero
transform.scale( scaling_factor ); 		// scale
transform.preConcatenate( t );  		// un-center

interp = new NearestNeighborInterpolatorFactory()

result = Views.interval( 
	Views.raster(
		RealViews.transform(
				Views.interpolate( Views.extendZero( img ), interp),
				transform )),
	img );

ui.show( "transformed", result )