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BoofCV is an open source Java library for real-time computer vision and robotics applications.
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/*
 * Copyright (c) 2011-2017, Peter Abeles. All Rights Reserved.
 *
 * This file is part of BoofCV (http://boofcv.org).
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package boofcv.alg.fiducial.qrcode;

import georegression.struct.point.Point2D_I32;
import org.ejml.data.BMatrixRMaj;

import java.util.ArrayList;
import java.util.List;

/**
 * Pre-computes which pixels in a QR code are data bits or not. (0,0) is top left corner of QR code. +x are columns
 * and +y are rows. This is needed because there is no simple equation which says what modules encode data and which
 * ones do it.
 *
 * @author Peter Abeles
 */
public class QrCodeCodeWordLocations extends BMatrixRMaj {

	public List bits = new ArrayList<>();

	public QrCodeCodeWordLocations(int numModules , int alignment[] , boolean hasVersion ) {
		super(numModules,numModules);
		computeFeatureMask(numModules, alignment, hasVersion);
		computeBitLocations();
	}

	public QrCodeCodeWordLocations( int version ) {
		this(QrCode.totalModules(version), QrCode.VERSION_INFO[version].alignment,version >= QrCode.VERSION_ENCODED_AT);
	}

	/**
	 * Blocks out the location of features in the image. Needed for codeworld location extraction
	 * @param numModules
	 * @param alignment
	 * @param hasVersion
	 */
	private void computeFeatureMask(int numModules, int[] alignment, boolean hasVersion) {
		// mark alignment patterns + format info
		markSquare(0,0,9);
		markRectangle(numModules-8,0,9,8);
		markRectangle(0,numModules-8,8,9);

		// timing pattern
		markRectangle(8,6,1,numModules-8-8);
		markRectangle(6,8,numModules-8-8,1);

		// version info
		if( hasVersion ) {
			markRectangle(numModules-11,0,6,3);
			markRectangle(0,numModules-11,3,6);
		}

		// alignment patterns
		for (int i = 0; i < alignment.length; i++) {
			int row = alignment[i];

			for (int j = 0; j < alignment.length; j++) {
				if( i == 0 & j == 0 )
					continue;
				if( i == alignment.length-1 & j == 0)
					continue;
				if( i == alignment.length-1 & j == alignment.length-1)
					continue;

				int col = alignment[j];
				markSquare(numModules-row-3,col-2,5);
			}
		}
	}

	private void markSquare( int row , int col , int width ) {
		for (int i = 0; i < width; i++) {
			for (int j = 0; j < width; j++) {
				set(row+i,col+j,true);
			}
		}
	}

	private void markRectangle( int row , int col , int width , int height ) {
		for (int i = 0; i < height; i++) {
			for (int j = 0; j < width; j++) {
				set(row+i,col+j,true);
			}
		}
	}

	/**
	 * Snakes through and specifies the location of each bit for all the code words in the grid.
	 */
	private void computeBitLocations() {
		int N = numRows;
		int row = N-1;
		int col = N-1;
		int direction = -1;

		while (col > 0) {
			if (col == 6)
				col -= 1;

			if (!get(row,col)) {
				bits.add( new Point2D_I32(col,row));
			}
			if (!get(row,col-1)) {
				bits.add( new Point2D_I32(col-1,row));
			}

			row += direction;

			if (row < 0 || row >= N) {
				direction = -direction;
				col -= 2;
				row += direction;
			}
		}
	}

	/**
	 * Returns number of data bits available.
	 */
	public int getTotalDataBits() {
		return numRows*numRows - sum();
	}
}