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Initial checkin of Data Matrix detector. Still needs work, and is not enabled by default.

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git-svn-id: https://zxing.googlecode.com/svn/trunk@545 59b500cc-1b3d-0410-9834-0bbf25fbcc57
This commit is contained in:
srowen 2008-08-04 18:37:42 +00:00
parent 44d5796673
commit 3a1d1f1850
2 changed files with 388 additions and 12 deletions
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15
core/src/com/google/zxing/datamatrix/DataMatrixReader.java
View file

@ -17,6 +17,7 @@
package com.google.zxing.datamatrix;
import com.google.zxing.BarcodeFormat;
import com.google.zxing.DecodeHintType;
import com.google.zxing.MonochromeBitmapSource;
import com.google.zxing.Reader;
import com.google.zxing.ReaderException;
@ -24,7 +25,9 @@ import com.google.zxing.Result;
import com.google.zxing.ResultPoint;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.common.DecoderResult;
import com.google.zxing.common.DetectorResult;
import com.google.zxing.datamatrix.decoder.Decoder;
import com.google.zxing.datamatrix.detector.Detector;
import java.util.Hashtable;
@ -53,15 +56,15 @@ public final class DataMatrixReader implements Reader {
throws ReaderException {
DecoderResult decoderResult;
ResultPoint[] points;
//if (hints != null && hints.containsKey(DecodeHintType.PURE_BARCODE)) {
if (hints != null && hints.containsKey(DecodeHintType.PURE_BARCODE)) {
BitMatrix bits = extractPureBits(image);
decoderResult = decoder.decode(bits);
points = NO_POINTS;
//} else {
// DetectorResult result = new Detector(image).detect();
// decoderResult = decoder.decode(result.getBits());
// points = result.getPoints();
//}
} else {
DetectorResult result = new Detector(image).detect();
decoderResult = decoder.decode(result.getBits());
points = result.getPoints();
}
return new Result(decoderResult.getText(), decoderResult.getRawBytes(), points, BarcodeFormat.DATAMATRIX);
}

385
core/src/com/google/zxing/datamatrix/detector/Detector.java
View file

@ -1,5 +1,5 @@
/*
* Copyright 2007 ZXing authors
* 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.
@ -18,16 +18,34 @@ package com.google.zxing.datamatrix.detector;
import com.google.zxing.MonochromeBitmapSource;
import com.google.zxing.ReaderException;
import com.google.zxing.ResultPoint;
import com.google.zxing.BlackPointEstimationMethod;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.common.Collections;
import com.google.zxing.common.Comparator;
import com.google.zxing.common.DetectorResult;
import com.google.zxing.common.GenericResultPoint;
import com.google.zxing.common.GridSampler;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Vector;
/**
* <p>Encapsulates logic that can detect a Data Matrix Code in an image, even if the Data Matrix Code
* is rotated or skewed, or partially obscured.</p>
*
* @author bbrown@google.com (Brian Brown)
* @author srowen@google.com (Sean Owen)
*/
public final class Detector {
private static final int MAX_MODULES = 32;
// Trick to avoid creating new Integer objects below -- a sort of crude copy of
// the Integer.valueOf(int) optimization added in Java 5, not in J2ME
private static final Integer[] INTEGERS =
{ new Integer(0), new Integer(1), new Integer(2), new Integer(3), new Integer(4) };
private final MonochromeBitmapSource image;
public Detector(MonochromeBitmapSource image) {
@ -35,15 +53,370 @@ public final class Detector {
}
/**
* <p>Detects a Data Matrix Code in an image, simply.</p>
* <p>Detects a Data Matrix Code in an image.</p>
*
* @return {@link DetectorResult} encapsulating results of detecting a QR Code
* @throws ReaderException if no Data Matrix Code can be found
*/
public DetectorResult detect() {
// TODO
return new DetectorResult(null, null);
public DetectorResult detect() throws ReaderException {
if (!BlackPointEstimationMethod.TWO_D_SAMPLING.equals(image.getLastEstimationMethod())) {
image.estimateBlackPoint(BlackPointEstimationMethod.TWO_D_SAMPLING, 0);
}
int height = image.getHeight();
int width = image.getWidth();
int halfHeight = height >> 1;
int halfWidth = width >> 1;
int iSkip = Math.max(1, height / (MAX_MODULES << 2));
int jSkip = Math.max(1, width / (MAX_MODULES << 2));
int minI = 0;
int maxI = height;
int minJ = 0;
int maxJ = width;
ResultPoint pointA = findCornerFromCenter(halfHeight, -iSkip, minI, maxI, halfWidth, 0, minJ, maxJ, halfWidth >> 2);
minI = (int) pointA.getY() - 1;
ResultPoint pointB = findCornerFromCenter(halfHeight, 0, minI, maxI, halfWidth, -jSkip, minJ, maxJ, halfHeight >> 2);
minJ = (int) pointB.getX() - 1;
ResultPoint pointC = findCornerFromCenter(halfHeight, 0, minI, maxI, halfWidth, jSkip, minJ, maxJ, halfHeight >> 2);
maxJ = (int) pointC.getX() + 1;
ResultPoint pointD = findCornerFromCenter(halfHeight, iSkip, minI, maxI, halfWidth, 0, minJ, maxJ, halfWidth >> 2);
maxI = (int) pointD.getY() + 1;
// Go try to find point A again with better information -- might have been off at first.
pointA = findCornerFromCenter(halfHeight, -iSkip, minI, maxI, halfWidth, 0, minJ, maxJ, halfWidth >> 2);
// Point A and D are across the diagonal from one another,
// as are B and C. Figure out which are the solid black lines
// by counting transitions
Vector transitions = new Vector(4);
transitions.addElement(transitionsBetween(pointA, pointB));
transitions.addElement(transitionsBetween(pointA, pointC));
transitions.addElement(transitionsBetween(pointB, pointD));
transitions.addElement(transitionsBetween(pointC, pointD));
Collections.insertionSort(transitions, new ResultPointsAndTransitionsComparator());
// Sort by number of transitions. First two will be the two solid sides; last two
// will be the two alternating black/white sides
ResultPointsAndTransitions lSideOne = (ResultPointsAndTransitions) transitions.elementAt(0);
ResultPointsAndTransitions lSideTwo = (ResultPointsAndTransitions) transitions.elementAt(1);
// Figure out which point is their intersection by tallying up the number of times we see the
// endpoints in the four endpoints. One will show up twice.
Hashtable pointCount = new Hashtable();
increment(pointCount, lSideOne.getFrom());
increment(pointCount, lSideOne.getTo());
increment(pointCount, lSideTwo.getFrom());
increment(pointCount, lSideTwo.getTo());
ResultPoint maybeTopLeft = null;
ResultPoint bottomLeft = null;
ResultPoint maybeBottomRight = null;
Enumeration points = pointCount.keys();
while (points.hasMoreElements()) {
ResultPoint point = (ResultPoint) points.nextElement();
Integer value = (Integer) pointCount.get(point);
if (value.intValue() == 2) {
bottomLeft = point; // this is definitely the bottom left, then -- end of two L sides
} else {
// Otherwise it's either top left or bottom right -- just assign the two arbitrarily now
if (maybeTopLeft == null) {
maybeTopLeft = point;
} else {
maybeBottomRight = point;
}
}
}
// Bottom left is correct but top left and bottom right might be switched
ResultPoint[] corners = new ResultPoint[] { maybeTopLeft, bottomLeft, maybeBottomRight };
// Use the dot product trick to sort them out
GenericResultPoint.orderBestPatterns(corners);
// Now we know which is which:
ResultPoint bottomRight = corners[0];
bottomLeft = corners[1];
ResultPoint topLeft = corners[2];
// Which point didn't we find in relation to the "L" sides? that's the top right corner
ResultPoint topRight;
if (!pointCount.containsKey(pointA)) {
topRight = pointA;
} else if (!pointCount.containsKey(pointB)) {
topRight = pointB;
} else if (!pointCount.containsKey(pointC)) {
topRight = pointC;
} else {
topRight = pointD;
}
// Next determine the dimension by tracing along the top or right side and counting black/white
// transitions. Since we start inside a black module, we should see a number of transitions
// equal to 1 less than the code dimension. Well, actually 2 less, because we are going to
// end on a black module:
// The top right point is actually the corner of a module, which is one of the two black modules
// adjacent to the white module at the top right. Tracing to that corner from either the top left
// or bottom right should work here, but, one will be more reliable since it's traced straight
// up or across, rather than at a slight angle. We use dot products to figure out which is
// better to use:
int dimension;
if (GenericResultPoint.crossProductZ(bottomLeft, bottomRight, topRight) <
GenericResultPoint.crossProductZ(topRight, topLeft, bottomLeft)) {
dimension = transitionsBetween(topLeft, topRight).getTransitions();
} else {
dimension = transitionsBetween(bottomRight, topRight).getTransitions();
}
dimension += 2;
BitMatrix bits = sampleGrid(image, topLeft, bottomLeft, bottomRight, dimension);
return new DetectorResult(bits, new ResultPoint[] {pointA, pointB, pointC, pointD});
}
/**
* Attempts to locate a corner of the barcode by scanning up, down, left or right from a center
* point which should be within the barcode.
*
* @param centerI center's i componennt (vertical)
* @param di change in i per step. If scanning up this is negative; down, positive; left or right, 0
* @param minI minimum value of i to search through (meaningless when di == 0)
* @param maxI maximum value of i
* @param centerJ center's j component (horizontal)
* @param dj same as di but change in j per step instead
* @param minJ see minI
* @param maxJ see minJ
* @param maxWhiteRun maximum run of white pixels that can still be considered to be within
* the barcode
* @return a {@link ResultPoint} encapsulating the corner that was found
* @throws ReaderException if such a point cannot be found
*/
private ResultPoint findCornerFromCenter(int centerI, int di, int minI, int maxI,
int centerJ, int dj, int minJ, int maxJ,
int maxWhiteRun) throws ReaderException {
int[] lastRange = null;
for (int i = centerI, j = centerJ;
i < maxI && i >= minI && j < maxJ && j >= minJ;
i += di, j += dj) {
int[] range;
if (dj == 0) {
// horizontal slices, up and down
range = blackWhiteRange(i, maxWhiteRun, minJ, maxJ, true);
} else {
// vertical slices, left and right
range = blackWhiteRange(j, maxWhiteRun, minI, maxI, false);
}
if (range == null) {
if (lastRange == null) {
throw new ReaderException("Center of image not within barcode");
}
// lastRange was found
if (dj == 0) {
int lastI = i - di;
if (lastRange[0] < centerJ) {
if (lastRange[1] > centerJ) {
// straddle, choose one or the other based on direction
return new GenericResultPoint(di > 0 ? lastRange[0] : lastRange[1], lastI);
}
return new GenericResultPoint(lastRange[0], lastI);
} else {
return new GenericResultPoint(lastRange[1], lastI);
}
} else {
int lastJ = j - dj;
if (lastRange[0] < centerI) {
if (lastRange[1] > centerI) {
return new GenericResultPoint(lastJ, dj < 0 ? lastRange[0] : lastRange[1]);
}
return new GenericResultPoint(lastJ, lastRange[0]);
} else {
return new GenericResultPoint(lastJ, lastRange[1]);
}
}
}
lastRange = range;
}
throw new ReaderException("Couldn't find an end to barcode");
}
/**
* Increments the Integer associated with a key by one.
*/
private static void increment(Hashtable table, ResultPoint key) {
Integer value = (Integer) table.get(key);
table.put(key, value == null ? INTEGERS[1] : INTEGERS[value.intValue() + 1]);
}
/**
* Computes the start and end of a region of pixels, either horizontally or vertically, that could be
* part of a Data Matrix barcode.
*
* @param fixedDimension if scanning horizontally, this is the row (the fixed vertical location) where
* we are scanning. If scanning vertically it's the colummn, the fixed horizontal location
* @param maxWhiteRun largest run of white pixels that can still be considered part of the barcode region
* @param minDim minimum pixel location, horizontally or vertically, to consider
* @param maxDim maximum pixel location, horizontally or vertically, to consider
* @param horizontal if true, we're scanning left-right, instead of up-down
* @return int[] with start and end of found range, or null if no such range is found (e.g. only white was found)
*/
private int[] blackWhiteRange(int fixedDimension, int maxWhiteRun, int minDim, int maxDim, boolean horizontal) {
int center = (minDim + maxDim) / 2;
// Scan left/up first
int start = center;
while (start >= minDim) {
if (horizontal ? image.isBlack(start, fixedDimension) : image.isBlack(fixedDimension, start)) {
start--;
} else {
int whiteRunStart = start;
do {
start--;
} while (start >= minDim &&
!(horizontal ? image.isBlack(start, fixedDimension) : image.isBlack(fixedDimension, start)));
int whiteRunSize = whiteRunStart - start;
if (start < minDim || whiteRunSize > maxWhiteRun) {
start = whiteRunStart + 1; // back up
break;
}
}
}
// Then try right/down
int end = center;
while (end < maxDim) {
if (horizontal ? image.isBlack(end, fixedDimension) : image.isBlack(fixedDimension, end)) {
end++;
} else {
int whiteRunStart = end;
do {
end++;
} while (end < maxDim &&
!(horizontal ? image.isBlack(end, fixedDimension) : image.isBlack(fixedDimension, end)));
int whiteRunSize = end - whiteRunStart;
if (end >= maxDim || whiteRunSize > maxWhiteRun) {
end = whiteRunStart - 1;
break;
}
}
}
if (end > start) {
return new int[] { start, end };
} else {
return null;
}
}
private static BitMatrix sampleGrid(MonochromeBitmapSource image,
ResultPoint topLeft,
ResultPoint bottomLeft,
ResultPoint bottomRight,
int dimension) throws ReaderException {
// We make up the top right point for now, based on the others.
// TODO: we actually found a fourth corner above and figured out which of two modules
// it was the corner of. We could use that here and adjust for perspective distortion.
float topRightX = (bottomRight.getX() - bottomLeft.getX()) + topLeft.getX();
float topRightY = (bottomRight.getY() - bottomLeft.getY()) + topLeft.getY();
// Note that unlike in the QR Code sampler, we didn't find the center of modules, but the
// very corners. So there is no 0.5f here; 0.0f is right.
GridSampler sampler = GridSampler.getInstance();
return sampler.sampleGrid(
image,
dimension,
0.0f,
0.0f,
dimension,
0.0f,
dimension,
dimension,
0.0f,
dimension,
topLeft.getX(),
topLeft.getY(),
topRightX,
topRightY,
bottomRight.getX(),
bottomRight.getY(),
bottomLeft.getX(),
bottomLeft.getY());
}
/**
* Counts the number of black/white transitions between two points, using something like Bresenham's algorithm.
*/
private ResultPointsAndTransitions transitionsBetween(ResultPoint from, ResultPoint to) {
// See QR Code Detector, sizeOfBlackWhiteBlackRun()
int fromX = (int) from.getX();
int fromY = (int) from.getY();
int toX = (int) to.getX();
int toY = (int) to.getY();
boolean steep = Math.abs(toY - fromY) > Math.abs(toX - fromX);
if (steep) {
int temp = fromX;
fromX = fromY;
fromY = temp;
temp = toX;
toX = toY;
toY = temp;
}
int dx = Math.abs(toX - fromX);
int dy = Math.abs(toY - fromY);
int error = -dx >> 1;
int ystep = fromY < toY ? 1 : -1;
int xstep = fromX < toX ? 1 : -1;
int transitions = 0;
boolean inBlack = image.isBlack(steep ? fromY : fromX, steep ? fromX : fromY);
for (int x = fromX, y = fromY; x != toX; x += xstep) {
boolean isBlack = image.isBlack(steep ? y : x, steep ? x : y);
if (isBlack == !inBlack) {
transitions++;
inBlack = isBlack;
}
error += dy;
if (error > 0) {
y += ystep;
error -= dx;
}
}
return new ResultPointsAndTransitions(from, to, transitions);
}
/**
* Simply encapsulates two points and a number of transitions between them.
*/
private static class ResultPointsAndTransitions {
private final ResultPoint from;
private final ResultPoint to;
private final int transitions;
private ResultPointsAndTransitions(ResultPoint from, ResultPoint to, int transitions) {
this.from = from;
this.to = to;
this.transitions = transitions;
}
public ResultPoint getFrom() {
return from;
}
public ResultPoint getTo() {
return to;
}
public int getTransitions() {
return transitions;
}
public String toString() {
return from + "/" + to + '/' + transitions;
}
}
/**
* Orders ResultPointsAndTransitions by number of transitions, ascending.
*/
private static class ResultPointsAndTransitionsComparator implements Comparator {
public int compare(Object o1, Object o2) {
return ((ResultPointsAndTransitions) o1).getTransitions() - ((ResultPointsAndTransitions) o2).getTransitions();
}
}
}