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1c4f85ee24
git-svn-id: https://zxing.googlecode.com/svn/trunk@820 59b500cc-1b3d-0410-9834-0bbf25fbcc57
425 lines
19 KiB
C#
425 lines
19 KiB
C#
/*
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* Copyright 2008 ZXing authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Text;
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using com.google.zxing;
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using com.google.zxing.common;
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namespace com.google.zxing.datamatrix.detector
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{
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/**
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* <p>Encapsulates logic that can detect a Data Matrix Code in an image, even if the Data Matrix Code
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* is rotated or skewed, or partially obscured.</p>
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*
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* @author Sean Owen
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*/
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public sealed class Detector
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{
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private static int MAX_MODULES = 32;
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// Trick to avoid creating new int objects below -- a sort of crude copy of
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// the int.valueOf(int) optimization added in Java 5, not in J2ME
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private static int[] intS =
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{0, 1, 2, 3, 4};
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private MonochromeBitmapSource image;
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public Detector(MonochromeBitmapSource image) {
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this.image = image;
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}
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/**
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* <p>Detects a Data Matrix Code in an image.</p>
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*
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* @return {@link DetectorResult} encapsulating results of detecting a QR Code
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* @throws ReaderException if no Data Matrix Code can be found
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*/
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public DetectorResult detect() {
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if (!BlackPointEstimationMethod.TWO_D_SAMPLING.Equals(image.getLastEstimationMethod())) {
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image.estimateBlackPoint(BlackPointEstimationMethod.TWO_D_SAMPLING, 0);
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}
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int height = image.getHeight();
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int width = image.getWidth();
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int halfHeight = height >> 1;
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int halfWidth = width >> 1;
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int iSkip = Math.Max(1, height / (MAX_MODULES << 3));
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int jSkip = Math.Max(1, width / (MAX_MODULES << 3));
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int minI = 0;
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int maxI = height;
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int minJ = 0;
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int maxJ = width;
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ResultPoint pointA = findCornerFromCenter(halfHeight, -iSkip, minI, maxI, halfWidth, 0, minJ, maxJ, halfWidth >> 1);
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minI = (int) pointA.getY() - 1;
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ResultPoint pointB = findCornerFromCenter(halfHeight, 0, minI, maxI, halfWidth, -jSkip, minJ, maxJ, halfHeight >> 1);
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minJ = (int) pointB.getX() - 1;
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ResultPoint pointC = findCornerFromCenter(halfHeight, 0, minI, maxI, halfWidth, jSkip, minJ, maxJ, halfHeight >> 1);
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maxJ = (int) pointC.getX() + 1;
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ResultPoint pointD = findCornerFromCenter(halfHeight, iSkip, minI, maxI, halfWidth, 0, minJ, maxJ, halfWidth >> 1);
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maxI = (int) pointD.getY() + 1;
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// Go try to find point A again with better information -- might have been off at first.
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pointA = findCornerFromCenter(halfHeight, -iSkip, minI, maxI, halfWidth, 0, minJ, maxJ, halfWidth >> 2);
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// Point A and D are across the diagonal from one another,
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// as are B and C. Figure out which are the solid black lines
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// by counting transitions
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System.Collections.ArrayList transitions = new System.Collections.ArrayList(4);
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transitions.Add(transitionsBetween(pointA, pointB));
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transitions.Add(transitionsBetween(pointA, pointC));
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transitions.Add(transitionsBetween(pointB, pointD));
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transitions.Add(transitionsBetween(pointC, pointD));
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Collections.insertionSort(transitions, new ResultPointsAndTransitionsComparator());
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// Sort by number of transitions. First two will be the two solid sides; last two
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// will be the two alternating black/white sides
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ResultPointsAndTransitions lSideOne = (ResultPointsAndTransitions) transitions[0];
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ResultPointsAndTransitions lSideTwo = (ResultPointsAndTransitions) transitions[1];
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// Figure out which point is their intersection by tallying up the number of times we see the
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// endpoints in the four endpoints. One will show up twice.
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System.Collections.Hashtable pointCount = new System.Collections.Hashtable();
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increment(pointCount, lSideOne.getFrom());
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increment(pointCount, lSideOne.getTo());
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increment(pointCount, lSideTwo.getFrom());
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increment(pointCount, lSideTwo.getTo());
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ResultPoint maybeTopLeft = null;
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ResultPoint bottomLeft = null;
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ResultPoint maybeBottomRight = null;
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System.Collections.IEnumerator points = pointCount.GetEnumerator();
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while (points.MoveNext()) {
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ResultPoint point = (ResultPoint) points.Current;
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int value = (int) pointCount[point];
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if (value == 2) {
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bottomLeft = point; // this is definitely the bottom left, then -- end of two L sides
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} else {
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// Otherwise it's either top left or bottom right -- just assign the two arbitrarily now
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if (maybeTopLeft == null) {
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maybeTopLeft = point;
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} else {
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maybeBottomRight = point;
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}
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}
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}
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if (maybeTopLeft == null || bottomLeft == null || maybeBottomRight == null) {
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throw new ReaderException();
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}
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// Bottom left is correct but top left and bottom right might be switched
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ResultPoint[] corners = { maybeTopLeft, bottomLeft, maybeBottomRight };
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// Use the dot product trick to sort them out
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GenericResultPoint.orderBestPatterns(corners);
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// Now we know which is which:
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ResultPoint bottomRight = corners[0];
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bottomLeft = corners[1];
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ResultPoint topLeft = corners[2];
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// Which point didn't we find in relation to the "L" sides? that's the top right corner
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ResultPoint topRight;
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if (!pointCount.ContainsKey(pointA)) {
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topRight = pointA;
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} else if (!pointCount.ContainsKey(pointB)) {
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topRight = pointB;
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} else if (!pointCount.ContainsKey(pointC)) {
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topRight = pointC;
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} else {
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topRight = pointD;
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}
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// Next determine the dimension by tracing along the top or right side and counting black/white
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// transitions. Since we start inside a black module, we should see a number of transitions
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// equal to 1 less than the code dimension. Well, actually 2 less, because we are going to
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// end on a black module:
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// The top right point is actually the corner of a module, which is one of the two black modules
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// adjacent to the white module at the top right. Tracing to that corner from either the top left
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// or bottom right should work here, but, one will be more reliable since it's traced straight
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// up or across, rather than at a slight angle. We use dot products to figure out which is
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// better to use:
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int dimension;
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if (GenericResultPoint.crossProductZ(bottomLeft, bottomRight, topRight) <
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GenericResultPoint.crossProductZ(topRight, topLeft, bottomLeft)) {
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dimension = transitionsBetween(topLeft, topRight).getTransitions();
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} else {
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dimension = transitionsBetween(bottomRight, topRight).getTransitions();
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}
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dimension += 2;
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BitMatrix bits = sampleGrid(image, topLeft, bottomLeft, bottomRight, dimension);
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return new DetectorResult(bits, new ResultPoint[] {pointA, pointB, pointC, pointD});
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}
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/**
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* Attempts to locate a corner of the barcode by scanning up, down, left or right from a center
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* point which should be within the barcode.
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*
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* @param centerI center's i componennt (vertical)
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* @param di change in i per step. If scanning up this is negative; down, positive; left or right, 0
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* @param minI minimum value of i to search through (meaningless when di == 0)
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* @param maxI maximum value of i
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* @param centerJ center's j component (horizontal)
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* @param dj same as di but change in j per step instead
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* @param minJ see minI
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* @param maxJ see minJ
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* @param maxWhiteRun maximum run of white pixels that can still be considered to be within
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* the barcode
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* @return a {@link ResultPoint} encapsulating the corner that was found
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* @throws ReaderException if such a point cannot be found
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*/
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private ResultPoint findCornerFromCenter(int centerI, int di, int minI, int maxI,
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int centerJ, int dj, int minJ, int maxJ,
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int maxWhiteRun) {
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int[] lastRange = null;
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for (int i = centerI, j = centerJ;
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i < maxI && i >= minI && j < maxJ && j >= minJ;
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i += di, j += dj) {
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int[] range;
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if (dj == 0) {
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// horizontal slices, up and down
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range = blackWhiteRange(i, maxWhiteRun, minJ, maxJ, true);
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} else {
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// vertical slices, left and right
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range = blackWhiteRange(j, maxWhiteRun, minI, maxI, false);
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}
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if (range == null) {
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if (lastRange == null) {
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throw new ReaderException();
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}
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// lastRange was found
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if (dj == 0) {
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int lastI = i - di;
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if (lastRange[0] < centerJ) {
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if (lastRange[1] > centerJ) {
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// straddle, choose one or the other based on direction
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return new GenericResultPoint(di > 0 ? lastRange[0] : lastRange[1], lastI);
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}
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return new GenericResultPoint(lastRange[0], lastI);
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} else {
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return new GenericResultPoint(lastRange[1], lastI);
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}
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} else {
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int lastJ = j - dj;
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if (lastRange[0] < centerI) {
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if (lastRange[1] > centerI) {
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return new GenericResultPoint(lastJ, dj < 0 ? lastRange[0] : lastRange[1]);
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}
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return new GenericResultPoint(lastJ, lastRange[0]);
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} else {
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return new GenericResultPoint(lastJ, lastRange[1]);
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}
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}
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}
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lastRange = range;
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}
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throw new ReaderException();
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}
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/**
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* Increments the int associated with a key by one.
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*/
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private static void increment(System.Collections.Hashtable table, ResultPoint key) {
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int value = (int) table[key];
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table[key] = value.Equals(null) ? intS[1] : intS[value + 1];
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//table.put(key, value == null ? intS[1] : intS[value.intValue() + 1]);
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}
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/**
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* Computes the start and end of a region of pixels, either horizontally or vertically, that could be
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* part of a Data Matrix barcode.
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*
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* @param fixedDimension if scanning horizontally, this is the row (the fixed vertical location) where
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* we are scanning. If scanning vertically it's the colummn, the fixed horizontal location
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* @param maxWhiteRun largest run of white pixels that can still be considered part of the barcode region
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* @param minDim minimum pixel location, horizontally or vertically, to consider
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* @param maxDim maximum pixel location, horizontally or vertically, to consider
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* @param horizontal if true, we're scanning left-right, instead of up-down
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* @return int[] with start and end of found range, or null if no such range is found (e.g. only white was found)
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*/
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private int[] blackWhiteRange(int fixedDimension, int maxWhiteRun, int minDim, int maxDim, bool horizontal) {
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int center = (minDim + maxDim) / 2;
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BitArray rowOrColumn = horizontal ? image.getBlackRow(fixedDimension, null, 0, image.getWidth())
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: image.getBlackColumn(fixedDimension, null, 0, image.getHeight());
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// Scan left/up first
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int start = center;
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while (start >= minDim) {
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if (rowOrColumn.get(start)) {
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start--;
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} else {
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int whiteRunStart = start;
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do {
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start--;
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} while (start >= minDim && !rowOrColumn.get(start));
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int whiteRunSize = whiteRunStart - start;
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if (start < minDim || whiteRunSize > maxWhiteRun) {
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start = whiteRunStart + 1; // back up
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break;
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}
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}
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}
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start++;
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// Then try right/down
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int end = center;
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while (end < maxDim) {
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if (rowOrColumn.get(end)) {
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end++;
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} else {
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int whiteRunStart = end;
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do {
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end++;
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} while (end < maxDim && !rowOrColumn.get(end));
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int whiteRunSize = end - whiteRunStart;
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if (end >= maxDim || whiteRunSize > maxWhiteRun) {
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end = whiteRunStart - 1;
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break;
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}
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}
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}
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end--;
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if (end > start) {
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return new int[] { start, end };
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} else {
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return null;
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}
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}
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private static BitMatrix sampleGrid(MonochromeBitmapSource image,
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ResultPoint topLeft,
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ResultPoint bottomLeft,
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ResultPoint bottomRight,
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int dimension) {
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// We make up the top right point for now, based on the others.
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// TODO: we actually found a fourth corner above and figured out which of two modules
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// it was the corner of. We could use that here and adjust for perspective distortion.
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float topRightX = (bottomRight.getX() - bottomLeft.getX()) + topLeft.getX();
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float topRightY = (bottomRight.getY() - bottomLeft.getY()) + topLeft.getY();
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// Note that unlike in the QR Code sampler, we didn't find the center of modules, but the
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// very corners. So there is no 0.5f here; 0.0f is right.
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GridSampler sampler = GridSampler.Instance;
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return sampler.sampleGrid(
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image,
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dimension,
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0.0f,
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0.0f,
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dimension,
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0.0f,
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dimension,
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dimension,
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0.0f,
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dimension,
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topLeft.getX(),
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topLeft.getY(),
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topRightX,
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topRightY,
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bottomRight.getX(),
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bottomRight.getY(),
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bottomLeft.getX(),
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bottomLeft.getY());
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}
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/**
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* Counts the number of black/white transitions between two points, using something like Bresenham's algorithm.
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*/
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private ResultPointsAndTransitions transitionsBetween(ResultPoint from, ResultPoint to) {
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// See QR Code Detector, sizeOfBlackWhiteBlackRun()
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int fromX = (int) from.getX();
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int fromY = (int) from.getY();
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int toX = (int) to.getX();
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int toY = (int) to.getY();
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bool steep = Math.Abs(toY - fromY) > Math.Abs(toX - fromX);
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if (steep) {
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int temp = fromX;
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fromX = fromY;
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fromY = temp;
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temp = toX;
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toX = toY;
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toY = temp;
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}
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int dx = Math.Abs(toX - fromX);
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int dy = Math.Abs(toY - fromY);
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int error = -dx >> 1;
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int ystep = fromY < toY ? 1 : -1;
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int xstep = fromX < toX ? 1 : -1;
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int transitions = 0;
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bool inBlack = image.isBlack(steep ? fromY : fromX, steep ? fromX : fromY);
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for (int x = fromX, y = fromY; x != toX; x += xstep) {
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bool isBlack = image.isBlack(steep ? y : x, steep ? x : y);
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if (isBlack == !inBlack) {
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transitions++;
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inBlack = isBlack;
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}
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error += dy;
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if (error > 0) {
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y += ystep;
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error -= dx;
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}
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}
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return new ResultPointsAndTransitions(from, to, transitions);
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}
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/**
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* Simply encapsulates two points and a number of transitions between them.
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*/
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private class ResultPointsAndTransitions {
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private ResultPoint from;
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private ResultPoint to;
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private int transitions;
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public ResultPointsAndTransitions(ResultPoint from, ResultPoint to, int transitions) {
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this.from = from;
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this.to = to;
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this.transitions = transitions;
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}
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public ResultPoint getFrom() {
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return from;
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}
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public ResultPoint getTo() {
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return to;
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}
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public int getTransitions() {
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return transitions;
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}
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public String toString() {
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return from + "/" + to + '/' + transitions;
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}
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}
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/**
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* Orders ResultPointsAndTransitions by number of transitions, ascending.
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*/
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private class ResultPointsAndTransitionsComparator : Comparator {
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public int compare(Object o1, Object o2) {
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return ((ResultPointsAndTransitions) o1).getTransitions() - ((ResultPointsAndTransitions) o2).getTransitions();
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}
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}
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}
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}
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