BinaryWeights_erodeByOne.java

package edu.stanford.rsl.tutorial.fan.redundancy;

import ij.ImageJ;
import edu.stanford.rsl.conrad.data.numeric.Grid2D;
import edu.stanford.rsl.conrad.data.numeric.Grid3D;
import edu.stanford.rsl.conrad.data.numeric.NumericPointwiseOperators;

public class BinaryWeights_erodeByOne extends Grid2D {

	private final double focalLength;
	private final double maxT;
	private final double deltaT, dLambda;
	private final int maxTIndex, maxLambdaIndex;
	private Grid2D binaryMask;

	public BinaryWeights_erodeByOne(final double focalLength, final double maxT,
			final double deltaT, double maxLambda, double dLambda) {
		// Call constructor from superclass
		super(((int) Math.round(maxT / deltaT)), ((int) Math.round(maxLambda / dLambda) + 1));
		
		// Initialize parameters
		this.focalLength = focalLength;
		this.maxT = maxT;
		this.deltaT = deltaT;
		this.dLambda = dLambda;
		this.maxLambdaIndex = (int) (Math.round(maxLambda / dLambda)) + 1;
		this.maxTIndex = (int) Math.round(maxT / deltaT);

		binaryMask = new Grid2D(this);
		createMask();
		createWeights();

		// Correct for scaling due to varying angle lambda
		NumericPointwiseOperators.multiplyBy(this, (float) (maxLambda / (Math.PI)));
	}

	private void createMask() {
		double lambda, delta;
		// iterate over the detector elements
		for (int t = 0; t < maxTIndex; ++t) {
			// compute delta of the current ray (detector element)
			delta = Math.atan((t * deltaT - maxT / 2.d + 0.5 * deltaT)
					/ focalLength);

			// iterate over the projection angles
			for (int b = 0; b < maxLambdaIndex; ++b) {
				// compute the current lambda angle
				lambda = b * dLambda;

				// Default weight is 1
				binaryMask.setAtIndex(maxTIndex - t - 1, b, 1.0f);
				this.setAtIndex(maxTIndex - t - 1, b, 1.0f);

				// First case: Handles weights for redundancies at the end of
				// the scan
				// Set weights to zero (Simulates the collimator)
				if (lambda >= (Math.PI + 2 * delta)) {
					binaryMask.setAtIndex(maxTIndex - t - 1, b, 0.f);
					this.setAtIndex(maxTIndex - t - 1, b, 0.f);
				}
			}
		}

	}

	private void createWeights() {
		Grid2D tmp = new Grid2D(this);
		NumericPointwiseOperators.fill(tmp, -100.f);

		// basically an dilation step!
		// iterate over the projection angles
		for (int b = 0; b < maxLambdaIndex; ++b) {
			// iterate over the detector elements
			for (int t = 0; t < maxTIndex; ++t) {
				if (t > 0) {
					if (this.getAtIndex(t, b) == 1 || this.getAtIndex(t-1, b) == 1) {
						tmp.setAtIndex(t, b, 1.f);
					} 
					else {
						tmp.setAtIndex(t, b, 0.f);
					}
				}
				if (t == 0)
				{
					tmp.setAtIndex(t, b, this.getAtIndex(t, b));
				}
			}
		}
		// iterate over the projection angles
		for (int b = 0; b < maxLambdaIndex; ++b) {
			// iterate over the detector elements
			for (int t = 0; t < maxTIndex; ++t) {
				this.setAtIndex(t, b, tmp.getAtIndex(t, b));
			}
		}

	}

	public Grid2D getBinaryMask() {
		return binaryMask;
	}

	public void applyToGrid(Grid2D sino) {
		NumericPointwiseOperators.multiplyBy(sino, this);
	}

	public static void main(String[] args) {
		// fan beam bp parameters

		double maxT = 400;
		double deltaT = 1.d;
		// set focal length according to the fan angle
		double focalLength = (maxT / 2.0 - 0.5)
				/ Math.tan(30.0 * Math.PI / 180.0);

		new ImageJ();
		Grid3D g = new Grid3D((int)maxT, 181, 360); 
		for (int i = 0; i < 360; ++i) { 
			double maxBeta = (double)(i+1) * Math.PI * 2.0 / 360.0;
			double deltaBeta = maxBeta / 180;

			BinaryWeights p = new BinaryWeights(focalLength, maxT, deltaT, maxBeta, deltaBeta); 
			g.setSubGrid(i, p); 
			//g.setSliceLabel("MaxBeta: " + Double.toString(maxBeta*180/Math.PI), i+1); }
		}
		g.show();


		double maxBeta = Math.PI;
		double deltaBeta = maxBeta / 180;

		BinaryWeights_erodeByOne p = new BinaryWeights_erodeByOne(focalLength, maxT, deltaT, maxBeta,
				deltaBeta);
		p.show("Weights");
		p.getBinaryMask().show("Mask");

	}

}
/*
 * Copyright (C) 2010-2014 Andreas Maier
 * CONRAD is developed as an Open Source project under the GNU General Public License (GPL).
*/