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Core barcode encoding/decoding library
/*
* Copyright 2008 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.qrcode.encoder;
/**
* @author Satoru Takabayashi
* @author Daniel Switkin
* @author Sean Owen
*/
final class MaskUtil {
// Penalty weights from section 6.8.2.1
private static final int N1 = 3;
private static final int N2 = 3;
private static final int N3 = 40;
private static final int N4 = 10;
private MaskUtil() {
// do nothing
}
/**
* Apply mask penalty rule 1 and return the penalty. Find repetitive cells with the same color and
* give penalty to them. Example: 00000 or 11111.
*/
static int applyMaskPenaltyRule1(ByteMatrix matrix) {
return applyMaskPenaltyRule1Internal(matrix, true) + applyMaskPenaltyRule1Internal(matrix, false);
}
/**
* Apply mask penalty rule 2 and return the penalty. Find 2x2 blocks with the same color and give
* penalty to them. This is actually equivalent to the spec's rule, which is to find MxN blocks and give a
* penalty proportional to (M-1)x(N-1), because this is the number of 2x2 blocks inside such a block.
*/
static int applyMaskPenaltyRule2(ByteMatrix matrix) {
int penalty = 0;
byte[][] array = matrix.getArray();
int width = matrix.getWidth();
int height = matrix.getHeight();
for (int y = 0; y < height - 1; y++) {
byte[] arrayY = array[y];
for (int x = 0; x < width - 1; x++) {
int value = arrayY[x];
if (value == arrayY[x + 1] && value == array[y + 1][x] && value == array[y + 1][x + 1]) {
penalty++;
}
}
}
return N2 * penalty;
}
/**
* Apply mask penalty rule 3 and return the penalty. Find consecutive runs of 1:1:3:1:1:4
* starting with black, or 4:1:1:3:1:1 starting with white, and give penalty to them. If we
* find patterns like 000010111010000, we give penalty once.
*/
static int applyMaskPenaltyRule3(ByteMatrix matrix) {
int numPenalties = 0;
byte[][] array = matrix.getArray();
int width = matrix.getWidth();
int height = matrix.getHeight();
for (int y = 0; y < height; y++) {
for (int x = 0; x < width; x++) {
byte[] arrayY = array[y]; // We can at least optimize this access
if (x + 6 < width &&
arrayY[x] == 1 &&
arrayY[x + 1] == 0 &&
arrayY[x + 2] == 1 &&
arrayY[x + 3] == 1 &&
arrayY[x + 4] == 1 &&
arrayY[x + 5] == 0 &&
arrayY[x + 6] == 1 &&
(isWhiteHorizontal(arrayY, x - 4, x) || isWhiteHorizontal(arrayY, x + 7, x + 11))) {
numPenalties++;
}
if (y + 6 < height &&
array[y][x] == 1 &&
array[y + 1][x] == 0 &&
array[y + 2][x] == 1 &&
array[y + 3][x] == 1 &&
array[y + 4][x] == 1 &&
array[y + 5][x] == 0 &&
array[y + 6][x] == 1 &&
(isWhiteVertical(array, x, y - 4, y) || isWhiteVertical(array, x, y + 7, y + 11))) {
numPenalties++;
}
}
}
return numPenalties * N3;
}
private static boolean isWhiteHorizontal(byte[] rowArray, int from, int to) {
from = Math.max(from, 0);
to = Math.min(to, rowArray.length);
for (int i = from; i < to; i++) {
if (rowArray[i] == 1) {
return false;
}
}
return true;
}
private static boolean isWhiteVertical(byte[][] array, int col, int from, int to) {
from = Math.max(from, 0);
to = Math.min(to, array.length);
for (int i = from; i < to; i++) {
if (array[i][col] == 1) {
return false;
}
}
return true;
}
/**
* Apply mask penalty rule 4 and return the penalty. Calculate the ratio of dark cells and give
* penalty if the ratio is far from 50%. It gives 10 penalty for 5% distance.
*/
static int applyMaskPenaltyRule4(ByteMatrix matrix) {
int numDarkCells = 0;
byte[][] array = matrix.getArray();
int width = matrix.getWidth();
int height = matrix.getHeight();
for (int y = 0; y < height; y++) {
byte[] arrayY = array[y];
for (int x = 0; x < width; x++) {
if (arrayY[x] == 1) {
numDarkCells++;
}
}
}
int numTotalCells = matrix.getHeight() * matrix.getWidth();
int fivePercentVariances = Math.abs(numDarkCells * 2 - numTotalCells) * 10 / numTotalCells;
return fivePercentVariances * N4;
}
/**
* Return the mask bit for "getMaskPattern" at "x" and "y". See 8.8 of JISX0510:2004 for mask
* pattern conditions.
*/
static boolean getDataMaskBit(int maskPattern, int x, int y) {
int intermediate;
int temp;
switch (maskPattern) {
case 0:
intermediate = (y + x) & 0x1;
break;
case 1:
intermediate = y & 0x1;
break;
case 2:
intermediate = x % 3;
break;
case 3:
intermediate = (y + x) % 3;
break;
case 4:
intermediate = ((y / 2) + (x / 3)) & 0x1;
break;
case 5:
temp = y * x;
intermediate = (temp & 0x1) + (temp % 3);
break;
case 6:
temp = y * x;
intermediate = ((temp & 0x1) + (temp % 3)) & 0x1;
break;
case 7:
temp = y * x;
intermediate = ((temp % 3) + ((y + x) & 0x1)) & 0x1;
break;
default:
throw new IllegalArgumentException("Invalid mask pattern: " + maskPattern);
}
return intermediate == 0;
}
/**
* Helper function for applyMaskPenaltyRule1. We need this for doing this calculation in both
* vertical and horizontal orders respectively.
*/
private static int applyMaskPenaltyRule1Internal(ByteMatrix matrix, boolean isHorizontal) {
int penalty = 0;
int iLimit = isHorizontal ? matrix.getHeight() : matrix.getWidth();
int jLimit = isHorizontal ? matrix.getWidth() : matrix.getHeight();
byte[][] array = matrix.getArray();
for (int i = 0; i < iLimit; i++) {
int numSameBitCells = 0;
int prevBit = -1;
for (int j = 0; j < jLimit; j++) {
int bit = isHorizontal ? array[i][j] : array[j][i];
if (bit == prevBit) {
numSameBitCells++;
} else {
if (numSameBitCells >= 5) {
penalty += N1 + (numSameBitCells - 5);
}
numSameBitCells = 1; // Include the cell itself.
prevBit = bit;
}
}
if (numSameBitCells >= 5) {
penalty += N1 + (numSameBitCells - 5);
}
}
return penalty;
}
}