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Core barcode encoding/decoding library
/*
* Copyright 2007 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.common;
import java.util.Arrays;
/**
* Represents a 2D matrix of bits. In function arguments below, and throughout the common
* module, x is the column position, and y is the row position. The ordering is always x, y.
* The origin is at the top-left.
*
* Internally the bits are represented in a 1-D array of 32-bit ints. However, each row begins
* with a new int. This is done intentionally so that we can copy out a row into a BitArray very
* efficiently.
*
* The ordering of bits is row-major. Within each int, the least significant bits are used first,
* meaning they represent lower x values. This is compatible with BitArray's implementation.
*
* @author Sean Owen
* @author [email protected] (Daniel Switkin)
*/
public final class BitMatrix implements Cloneable {
private final int width;
private final int height;
private final int rowSize;
private final int[] bits;
// A helper to construct a square matrix.
public BitMatrix(int dimension) {
this(dimension, dimension);
}
public BitMatrix(int width, int height) {
if (width < 1 || height < 1) {
throw new IllegalArgumentException("Both dimensions must be greater than 0");
}
this.width = width;
this.height = height;
this.rowSize = (width + 31) >> 5;
bits = new int[rowSize * height];
}
private BitMatrix(int width, int height, int rowSize, int[] bits) {
this.width = width;
this.height = height;
this.rowSize = rowSize;
this.bits = bits;
}
/**
* Gets the requested bit, where true means black.
*
* @param x The horizontal component (i.e. which column)
* @param y The vertical component (i.e. which row)
* @return value of given bit in matrix
*/
public boolean get(int x, int y) {
int offset = y * rowSize + (x >> 5);
return ((bits[offset] >>> (x & 0x1f)) & 1) != 0;
}
/**
* Sets the given bit to true.
*
* @param x The horizontal component (i.e. which column)
* @param y The vertical component (i.e. which row)
*/
public void set(int x, int y) {
int offset = y * rowSize + (x >> 5);
bits[offset] |= 1 << (x & 0x1f);
}
/**
* Flips the given bit.
*
* @param x The horizontal component (i.e. which column)
* @param y The vertical component (i.e. which row)
*/
public void flip(int x, int y) {
int offset = y * rowSize + (x >> 5);
bits[offset] ^= 1 << (x & 0x1f);
}
/**
* Clears all bits (sets to false).
*/
public void clear() {
int max = bits.length;
for (int i = 0; i < max; i++) {
bits[i] = 0;
}
}
/**
* Sets a square region of the bit matrix to true.
*
* @param left The horizontal position to begin at (inclusive)
* @param top The vertical position to begin at (inclusive)
* @param width The width of the region
* @param height The height of the region
*/
public void setRegion(int left, int top, int width, int height) {
if (top < 0 || left < 0) {
throw new IllegalArgumentException("Left and top must be nonnegative");
}
if (height < 1 || width < 1) {
throw new IllegalArgumentException("Height and width must be at least 1");
}
int right = left + width;
int bottom = top + height;
if (bottom > this.height || right > this.width) {
throw new IllegalArgumentException("The region must fit inside the matrix");
}
for (int y = top; y < bottom; y++) {
int offset = y * rowSize;
for (int x = left; x < right; x++) {
bits[offset + (x >> 5)] |= 1 << (x & 0x1f);
}
}
}
/**
* A fast method to retrieve one row of data from the matrix as a BitArray.
*
* @param y The row to retrieve
* @param row An optional caller-allocated BitArray, will be allocated if null or too small
* @return The resulting BitArray - this reference should always be used even when passing
* your own row
*/
public BitArray getRow(int y, BitArray row) {
if (row == null || row.getSize() < width) {
row = new BitArray(width);
} else {
row.clear();
}
int offset = y * rowSize;
for (int x = 0; x < rowSize; x++) {
row.setBulk(x << 5, bits[offset + x]);
}
return row;
}
/**
* @param y row to set
* @param row {@link BitArray} to copy from
*/
public void setRow(int y, BitArray row) {
System.arraycopy(row.getBitArray(), 0, bits, y * rowSize, rowSize);
}
/**
* Modifies this {@code BitMatrix} to represent the same but rotated 180 degrees
*/
public void rotate180() {
int width = getWidth();
int height = getHeight();
BitArray topRow = new BitArray(width);
BitArray bottomRow = new BitArray(width);
for (int i = 0; i < (height+1) / 2; i++) {
topRow = getRow(i, topRow);
bottomRow = getRow(height - 1 - i, bottomRow);
topRow.reverse();
bottomRow.reverse();
setRow(i, bottomRow);
setRow(height - 1 - i, topRow);
}
}
/**
* This is useful in detecting the enclosing rectangle of a 'pure' barcode.
*
* @return {@code left,top,width,height} enclosing rectangle of all 1 bits, or null if it is all white
*/
public int[] getEnclosingRectangle() {
int left = width;
int top = height;
int right = -1;
int bottom = -1;
for (int y = 0; y < height; y++) {
for (int x32 = 0; x32 < rowSize; x32++) {
int theBits = bits[y * rowSize + x32];
if (theBits != 0) {
if (y < top) {
top = y;
}
if (y > bottom) {
bottom = y;
}
if (x32 * 32 < left) {
int bit = 0;
while ((theBits << (31 - bit)) == 0) {
bit++;
}
if ((x32 * 32 + bit) < left) {
left = x32 * 32 + bit;
}
}
if (x32 * 32 + 31 > right) {
int bit = 31;
while ((theBits >>> bit) == 0) {
bit--;
}
if ((x32 * 32 + bit) > right) {
right = x32 * 32 + bit;
}
}
}
}
}
int width = right - left;
int height = bottom - top;
if (width < 0 || height < 0) {
return null;
}
return new int[] {left, top, width, height};
}
/**
* This is useful in detecting a corner of a 'pure' barcode.
*
* @return {@code x,y} coordinate of top-left-most 1 bit, or null if it is all white
*/
public int[] getTopLeftOnBit() {
int bitsOffset = 0;
while (bitsOffset < bits.length && bits[bitsOffset] == 0) {
bitsOffset++;
}
if (bitsOffset == bits.length) {
return null;
}
int y = bitsOffset / rowSize;
int x = (bitsOffset % rowSize) << 5;
int theBits = bits[bitsOffset];
int bit = 0;
while ((theBits << (31-bit)) == 0) {
bit++;
}
x += bit;
return new int[] {x, y};
}
public int[] getBottomRightOnBit() {
int bitsOffset = bits.length - 1;
while (bitsOffset >= 0 && bits[bitsOffset] == 0) {
bitsOffset--;
}
if (bitsOffset < 0) {
return null;
}
int y = bitsOffset / rowSize;
int x = (bitsOffset % rowSize) << 5;
int theBits = bits[bitsOffset];
int bit = 31;
while ((theBits >>> bit) == 0) {
bit--;
}
x += bit;
return new int[] {x, y};
}
/**
* @return The width of the matrix
*/
public int getWidth() {
return width;
}
/**
* @return The height of the matrix
*/
public int getHeight() {
return height;
}
@Override
public boolean equals(Object o) {
if (!(o instanceof BitMatrix)) {
return false;
}
BitMatrix other = (BitMatrix) o;
return width == other.width && height == other.height && rowSize == other.rowSize &&
Arrays.equals(bits, other.bits);
}
@Override
public int hashCode() {
int hash = width;
hash = 31 * hash + width;
hash = 31 * hash + height;
hash = 31 * hash + rowSize;
hash = 31 * hash + Arrays.hashCode(bits);
return hash;
}
@Override
public String toString() {
StringBuilder result = new StringBuilder(height * (width + 1));
for (int y = 0; y < height; y++) {
for (int x = 0; x < width; x++) {
result.append(get(x, y) ? "X " : " ");
}
result.append('\n');
}
return result.toString();
}
@Override
public BitMatrix clone() {
return new BitMatrix(width, height, rowSize, bits.clone());
}
}
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