mirror of
https://github.com/zxing/zxing.git
synced 2025-01-28 03:21:49 -08:00
7854d30103
git-svn-id: https://zxing.googlecode.com/svn/trunk@817 59b500cc-1b3d-0410-9834-0bbf25fbcc57
258 lines
11 KiB
C#
Executable file
258 lines
11 KiB
C#
Executable file
/*
|
|
* 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.
|
|
*/
|
|
using System;
|
|
using com.google.zxing;
|
|
using com.google.zxing.common;
|
|
|
|
namespace com.google.zxing.qrcode.detector
|
|
{
|
|
public sealed class AlignmentPatternFinder
|
|
{
|
|
private MonochromeBitmapSource image;
|
|
private System.Collections.ArrayList possibleCenters;
|
|
private int startX;
|
|
private int startY;
|
|
private int width;
|
|
private int height;
|
|
private float moduleSize;
|
|
private int[] crossCheckStateCount;
|
|
|
|
/**
|
|
* <p>Creates a finder that will look in a portion of the whole image.</p>
|
|
*
|
|
* @param image image to search
|
|
* @param startX left column from which to start searching
|
|
* @param startY top row from which to start searching
|
|
* @param width width of region to search
|
|
* @param height height of region to search
|
|
* @param moduleSize estimated module size so far
|
|
*/
|
|
public AlignmentPatternFinder(MonochromeBitmapSource image,
|
|
int startX,
|
|
int startY,
|
|
int width,
|
|
int height,
|
|
float moduleSize) {
|
|
this.image = image;
|
|
this.possibleCenters = new System.Collections.ArrayList(5);
|
|
this.startX = startX;
|
|
this.startY = startY;
|
|
this.width = width;
|
|
this.height = height;
|
|
this.moduleSize = moduleSize;
|
|
this.crossCheckStateCount = new int[3];
|
|
}
|
|
|
|
/**
|
|
* <p>This method attempts to find the bottom-right alignment pattern in the image. It is a bit messy since
|
|
* it's pretty performance-critical and so is written to be fast foremost.</p>
|
|
*
|
|
* @return {@link AlignmentPattern} if found
|
|
* @throws ReaderException if not found
|
|
*/
|
|
public AlignmentPattern find() {
|
|
int startX = this.startX;
|
|
int height = this.height;
|
|
int maxJ = startX + width;
|
|
int middleI = startY + (height >> 1);
|
|
BitArray luminanceRow = new BitArray(width);
|
|
// We are looking for black/white/black modules in 1:1:1 ratio;
|
|
// this tracks the number of black/white/black modules seen so far
|
|
int[] stateCount = new int[3];
|
|
for (int iGen = 0; iGen < height; iGen++) {
|
|
// Search from middle outwards
|
|
int i = middleI + ((iGen & 0x01) == 0 ? ((iGen + 1) >> 1) : -((iGen + 1) >> 1));
|
|
image.getBlackRow(i, luminanceRow, startX, width);
|
|
stateCount[0] = 0;
|
|
stateCount[1] = 0;
|
|
stateCount[2] = 0;
|
|
int j = startX;
|
|
// Burn off leading white pixels before anything else; if we start in the middle of
|
|
// a white run, it doesn't make sense to count its length, since we don't know if the
|
|
// white run continued to the left of the start point
|
|
while (j < maxJ && !luminanceRow.get(j - startX)) {
|
|
j++;
|
|
}
|
|
int currentState = 0;
|
|
while (j < maxJ) {
|
|
if (luminanceRow.get(j - startX)) {
|
|
// Black pixel
|
|
if (currentState == 1) { // Counting black pixels
|
|
stateCount[currentState]++;
|
|
} else { // Counting white pixels
|
|
if (currentState == 2) { // A winner?
|
|
if (foundPatternCross(stateCount)) { // Yes
|
|
AlignmentPattern confirmed = handlePossibleCenter(stateCount, i, j);
|
|
if (confirmed != null) {
|
|
return confirmed;
|
|
}
|
|
}
|
|
stateCount[0] = stateCount[2];
|
|
stateCount[1] = 1;
|
|
stateCount[2] = 0;
|
|
currentState = 1;
|
|
} else {
|
|
stateCount[++currentState]++;
|
|
}
|
|
}
|
|
} else { // White pixel
|
|
if (currentState == 1) { // Counting black pixels
|
|
currentState++;
|
|
}
|
|
stateCount[currentState]++;
|
|
}
|
|
j++;
|
|
}
|
|
if (foundPatternCross(stateCount)) {
|
|
AlignmentPattern confirmed = handlePossibleCenter(stateCount, i, maxJ);
|
|
if (confirmed != null) {
|
|
return confirmed;
|
|
}
|
|
}
|
|
|
|
}
|
|
|
|
// Hmm, nothing we saw was observed and confirmed twice. If we had
|
|
// any guess at all, return it.
|
|
if (!(possibleCenters.Count==0)) {
|
|
return (AlignmentPattern) possibleCenters[0];
|
|
}
|
|
|
|
throw new ReaderException();
|
|
}
|
|
|
|
/**
|
|
* Given a count of black/white/black pixels just seen and an end position,
|
|
* figures the location of the center of this black/white/black run.
|
|
*/
|
|
private static float centerFromEnd(int[] stateCount, int end) {
|
|
return (float) (end - stateCount[2]) - stateCount[1] / 2.0f;
|
|
}
|
|
|
|
/**
|
|
* @param stateCount count of black/white/black pixels just read
|
|
* @return true iff the proportions of the counts is close enough to the 1/1/1 ratios
|
|
* used by alignment patterns to be considered a match
|
|
*/
|
|
private bool foundPatternCross(int[] stateCount) {
|
|
float moduleSize = this.moduleSize;
|
|
float maxVariance = moduleSize / 2.0f;
|
|
for (int i = 0; i < 3; i++) {
|
|
if (Math.Abs(moduleSize - stateCount[i]) >= maxVariance) {
|
|
return false;
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/**
|
|
* <p>After a horizontal scan finds a potential alignment pattern, this method
|
|
* "cross-checks" by scanning down vertically through the center of the possible
|
|
* alignment pattern to see if the same proportion is detected.</p>
|
|
*
|
|
* @param startI row where an alignment pattern was detected
|
|
* @param centerJ center of the section that appears to cross an alignment pattern
|
|
* @param maxCount maximum reasonable number of modules that should be
|
|
* observed in any reading state, based on the results of the horizontal scan
|
|
* @return vertical center of alignment pattern, or {@link Float#NaN} if not found
|
|
*/
|
|
private float crossCheckVertical(int startI, int centerJ, int maxCount, int originalStateCountTotal) {
|
|
MonochromeBitmapSource image = this.image;
|
|
|
|
int maxI = image.getHeight();
|
|
int[] stateCount = crossCheckStateCount;
|
|
stateCount[0] = 0;
|
|
stateCount[1] = 0;
|
|
stateCount[2] = 0;
|
|
|
|
// Start counting up from center
|
|
int i = startI;
|
|
while (i >= 0 && image.isBlack(centerJ, i) && stateCount[1] <= maxCount) {
|
|
stateCount[1]++;
|
|
i--;
|
|
}
|
|
// If already too many modules in this state or ran off the edge:
|
|
if (i < 0 || stateCount[1] > maxCount) {
|
|
return float.NaN;
|
|
}
|
|
while (i >= 0 && !image.isBlack(centerJ, i) && stateCount[0] <= maxCount) {
|
|
stateCount[0]++;
|
|
i--;
|
|
}
|
|
if (stateCount[0] > maxCount) {
|
|
return float.NaN;
|
|
}
|
|
|
|
// Now also count down from center
|
|
i = startI + 1;
|
|
while (i < maxI && image.isBlack(centerJ, i) && stateCount[1] <= maxCount) {
|
|
stateCount[1]++;
|
|
i++;
|
|
}
|
|
if (i == maxI || stateCount[1] > maxCount) {
|
|
return float.NaN;
|
|
}
|
|
while (i < maxI && !image.isBlack(centerJ, i) && stateCount[2] <= maxCount) {
|
|
stateCount[2]++;
|
|
i++;
|
|
}
|
|
if (stateCount[2] > maxCount) {
|
|
return float.NaN;
|
|
}
|
|
|
|
int stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2];
|
|
if (5 * Math.Abs(stateCountTotal - originalStateCountTotal) >= originalStateCountTotal) {
|
|
return float.NaN;
|
|
}
|
|
|
|
return foundPatternCross(stateCount) ? centerFromEnd(stateCount, i) : float.NaN;
|
|
}
|
|
|
|
/**
|
|
* <p>This is called when a horizontal scan finds a possible alignment pattern. It will
|
|
* cross check with a vertical scan, and if successful, will see if this pattern had been
|
|
* found on a previous horizontal scan. If so, we consider it confirmed and conclude we have
|
|
* found the alignment pattern.</p>
|
|
*
|
|
* @param stateCount reading state module counts from horizontal scan
|
|
* @param i row where alignment pattern may be found
|
|
* @param j end of possible alignment pattern in row
|
|
* @return {@link AlignmentPattern} if we have found the same pattern twice, or null if not
|
|
*/
|
|
private AlignmentPattern handlePossibleCenter(int[] stateCount, int i, int j) {
|
|
int stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2];
|
|
float centerJ = centerFromEnd(stateCount, j);
|
|
float centerI = crossCheckVertical(i, (int) centerJ, 2 * stateCount[1], stateCountTotal);
|
|
if (!Single.IsNaN(centerI))
|
|
{
|
|
float estimatedModuleSize = (float) (stateCount[0] + stateCount[1] + stateCount[2]) / 3.0f;
|
|
int max = possibleCenters.Count;
|
|
for (int index = 0; index < max; index++) {
|
|
AlignmentPattern center = (AlignmentPattern) possibleCenters[index];
|
|
// Look for about the same center and module size:
|
|
if (center.aboutEquals(estimatedModuleSize, centerI, centerJ)) {
|
|
return new AlignmentPattern(centerJ, centerI, estimatedModuleSize);
|
|
}
|
|
}
|
|
// Hadn't found this before; save it
|
|
possibleCenters.Add(new AlignmentPattern(centerJ, centerI, estimatedModuleSize));
|
|
}
|
|
return null;
|
|
}
|
|
|
|
|
|
}
|
|
} |