BinaryBitmap.java

/*
 * Copyright 2009 ZXing authors
 *
 * 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 com.google.zxing;

import com.google.zxing.common.BitArray;
import com.google.zxing.common.BitMatrix;

/**
 * This class is the core bitmap class used by ZXing to represent 1 bit data.
 * Reader objects accept a BinaryBitmap and attempt to decode it.
 * 
 * @author dswitkin@google.com (Daniel Switkin)
 */
public final class BinaryBitmap {

	private final Binarizer binarizer;
	private BitMatrix matrix;

	public BinaryBitmap(Binarizer binarizer) {
		if (binarizer == null) {
			throw new IllegalArgumentException("Binarizer must be non-null.");
		}
		this.binarizer = binarizer;
	}

	/**
	 * @return The width of the bitmap.
	 */
	public int getWidth() {
		return binarizer.getWidth();
	}

	/**
	 * @return The height of the bitmap.
	 */
	public int getHeight() {
		return binarizer.getHeight();
	}

	/**
	 * Converts one row of luminance data to 1 bit data. May actually do the
	 * conversion, or return cached data. Callers should assume this method is
	 * expensive and call it as seldom as possible. This method is intended for
	 * decoding 1D barcodes and may choose to apply sharpening.
	 * 
	 * @param y
	 *            The row to fetch, which must be in [0, bitmap height)
	 * @param row
	 *            An optional preallocated array. If null or too small, it will
	 *            be ignored. If used, the Binarizer will call BitArray.clear().
	 *            Always use the returned object.
	 * @return The array of bits for this row (true means black).
	 * @throws NotFoundException
	 *             if row can't be binarized
	 */
	public BitArray getBlackRow(int y, BitArray row) throws NotFoundException {
		return binarizer.getBlackRow(y, row);
	}

	/**
	 * Converts a 2D array of luminance data to 1 bit. As above, assume this
	 * method is expensive and do not call it repeatedly. This method is
	 * intended for decoding 2D barcodes and may or may not apply sharpening.
	 * Therefore, a row from this matrix may not be identical to one fetched
	 * using getBlackRow(), so don't mix and match between them.
	 * 
	 * @return The 2D array of bits for the image (true means black).
	 * @throws NotFoundException
	 *             if image can't be binarized to make a matrix
	 */
	public BitMatrix getBlackMatrix() throws NotFoundException {
		// The matrix is created on demand the first time it is requested, then
		// cached. There are two
		// reasons for this:
		// 1. This work will never be done if the caller only installs 1D Reader
		// objects, or if a
		// 1D Reader finds a barcode before the 2D Readers run.
		// 2. This work will only be done once even if the caller installs
		// multiple 2D Readers.
		if (matrix == null) {
			matrix = binarizer.getBlackMatrix();
		}
		return matrix;
	}

	/**
	 * @return Whether this bitmap can be cropped.
	 */
	public boolean isCropSupported() {
		return binarizer.getLuminanceSource().isCropSupported();
	}

	/**
	 * Returns a new object with cropped image data. Implementations may keep a
	 * reference to the original data rather than a copy. Only callable if
	 * isCropSupported() is true.
	 * 
	 * @param left
	 *            The left coordinate, which must be in [0,getWidth())
	 * @param top
	 *            The top coordinate, which must be in [0,getHeight())
	 * @param width
	 *            The width of the rectangle to crop.
	 * @param height
	 *            The height of the rectangle to crop.
	 * @return A cropped version of this object.
	 */
	public BinaryBitmap crop(int left, int top, int width, int height) {
		LuminanceSource newSource = binarizer.getLuminanceSource().crop(left,
				top, width, height);
		return new BinaryBitmap(binarizer.createBinarizer(newSource));
	}

	/**
	 * @return Whether this bitmap supports counter-clockwise rotation.
	 */
	public boolean isRotateSupported() {
		return binarizer.getLuminanceSource().isRotateSupported();
	}

	/**
	 * Returns a new object with rotated image data by 90 degrees
	 * counterclockwise. Only callable if {@link #isRotateSupported()} is true.
	 * 
	 * @return A rotated version of this object.
	 */
	public BinaryBitmap rotateCounterClockwise() {
		LuminanceSource newSource = binarizer.getLuminanceSource()
				.rotateCounterClockwise();
		return new BinaryBitmap(binarizer.createBinarizer(newSource));
	}

	/**
	 * Returns a new object with rotated image data by 45 degrees
	 * counterclockwise. Only callable if {@link #isRotateSupported()} is true.
	 * 
	 * @return A rotated version of this object.
	 */
	public BinaryBitmap rotateCounterClockwise45() {
		LuminanceSource newSource = binarizer.getLuminanceSource()
				.rotateCounterClockwise45();
		return new BinaryBitmap(binarizer.createBinarizer(newSource));
	}

	@Override
	public String toString() {
		try {
			return getBlackMatrix().toString();
		} catch (NotFoundException e) {
			return "";
		}
	}

}