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d4efd44fb0
git-svn-id: https://zxing.googlecode.com/svn/trunk@1202 59b500cc-1b3d-0410-9834-0bbf25fbcc57
646 lines
23 KiB
C#
Executable file
646 lines
23 KiB
C#
Executable file
/*
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* Copyright 2007 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 DecodeHintType = com.google.zxing.DecodeHintType;
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using ReaderException = com.google.zxing.ReaderException;
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using ResultPoint = com.google.zxing.ResultPoint;
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using ResultPointCallback = com.google.zxing.ResultPointCallback;
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using Collections = com.google.zxing.common.Collections;
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using Comparator = com.google.zxing.common.Comparator;
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using BitMatrix = com.google.zxing.common.BitMatrix;
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namespace com.google.zxing.qrcode.detector
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{
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/// <summary> <p>This class attempts to find finder patterns in a QR Code. Finder patterns are the square
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/// markers at three corners of a QR Code.</p>
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///
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/// <p>This class is thread-safe but not reentrant. Each thread must allocate its own object.
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///
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/// </summary>
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/// <author> Sean Owen
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/// </author>
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/// <author>www.Redivivus.in (suraj.supekar@redivivus.in) - Ported from ZXING Java Source
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/// </author>
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public class FinderPatternFinder
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{
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virtual protected internal BitMatrix Image
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{
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get
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{
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return image;
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}
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}
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virtual protected internal System.Collections.ArrayList PossibleCenters
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{
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get
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{
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return possibleCenters;
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}
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}
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private int[] CrossCheckStateCount
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{
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get
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{
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crossCheckStateCount[0] = 0;
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crossCheckStateCount[1] = 0;
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crossCheckStateCount[2] = 0;
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crossCheckStateCount[3] = 0;
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crossCheckStateCount[4] = 0;
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return crossCheckStateCount;
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}
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}
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private const int CENTER_QUORUM = 2;
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protected internal const int MIN_SKIP = 3; // 1 pixel/module times 3 modules/center
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protected internal const int MAX_MODULES = 57; // support up to version 10 for mobile clients
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private const int INTEGER_MATH_SHIFT = 8;
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//UPGRADE_NOTE: Final was removed from the declaration of 'image '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
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private BitMatrix image;
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//UPGRADE_NOTE: Final was removed from the declaration of 'possibleCenters '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
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private System.Collections.ArrayList possibleCenters;
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private bool hasSkipped;
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//UPGRADE_NOTE: Final was removed from the declaration of 'crossCheckStateCount '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
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private int[] crossCheckStateCount;
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//UPGRADE_NOTE: Final was removed from the declaration of 'resultPointCallback '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
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private ResultPointCallback resultPointCallback;
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/// <summary> <p>Creates a finder that will search the image for three finder patterns.</p>
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///
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/// </summary>
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/// <param name="image">image to search
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/// </param>
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public FinderPatternFinder(BitMatrix image):this(image, null)
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{
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}
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public FinderPatternFinder(BitMatrix image, ResultPointCallback resultPointCallback)
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{
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this.image = image;
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this.possibleCenters = System.Collections.ArrayList.Synchronized(new System.Collections.ArrayList(10));
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this.crossCheckStateCount = new int[5];
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this.resultPointCallback = resultPointCallback;
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}
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internal virtual FinderPatternInfo find(System.Collections.Hashtable hints)
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{
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bool tryHarder = hints != null && hints.ContainsKey(DecodeHintType.TRY_HARDER);
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int maxI = image.Height;
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int maxJ = image.Width;
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// We are looking for black/white/black/white/black modules in
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// 1:1:3:1:1 ratio; this tracks the number of such modules seen so far
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// Let's assume that the maximum version QR Code we support takes up 1/4 the height of the
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// image, and then account for the center being 3 modules in size. This gives the smallest
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// number of pixels the center could be, so skip this often. When trying harder, look for all
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// QR versions regardless of how dense they are.
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int iSkip = (3 * maxI) / (4 * MAX_MODULES);
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if (iSkip < MIN_SKIP || tryHarder)
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{
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iSkip = MIN_SKIP;
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}
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bool done = false;
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int[] stateCount = new int[5];
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for (int i = iSkip - 1; i < maxI && !done; i += iSkip)
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{
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// Get a row of black/white values
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stateCount[0] = 0;
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stateCount[1] = 0;
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stateCount[2] = 0;
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stateCount[3] = 0;
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stateCount[4] = 0;
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int currentState = 0;
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for (int j = 0; j < maxJ; j++)
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{
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if (image.get_Renamed(j, i))
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{
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// Black pixel
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if ((currentState & 1) == 1)
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{
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// Counting white pixels
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currentState++;
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}
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stateCount[currentState]++;
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}
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else
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{
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// White pixel
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if ((currentState & 1) == 0)
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{
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// Counting black pixels
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if (currentState == 4)
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{
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// A winner?
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if (foundPatternCross(stateCount))
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{
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// Yes
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bool confirmed = handlePossibleCenter(stateCount, i, j);
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if (confirmed)
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{
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// Start examining every other line. Checking each line turned out to be too
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// expensive and didn't improve performance.
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iSkip = 2;
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if (hasSkipped)
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{
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done = haveMultiplyConfirmedCenters();
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}
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else
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{
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int rowSkip = findRowSkip();
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if (rowSkip > stateCount[2])
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{
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// Skip rows between row of lower confirmed center
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// and top of presumed third confirmed center
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// but back up a bit to get a full chance of detecting
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// it, entire width of center of finder pattern
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// Skip by rowSkip, but back off by stateCount[2] (size of last center
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// of pattern we saw) to be conservative, and also back off by iSkip which
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// is about to be re-added
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i += rowSkip - stateCount[2] - iSkip;
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j = maxJ - 1;
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}
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}
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}
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else
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{
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// Advance to next black pixel
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do
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{
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j++;
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}
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while (j < maxJ && !image.get_Renamed(j, i));
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j--; // back up to that last white pixel
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}
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// Clear state to start looking again
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currentState = 0;
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stateCount[0] = 0;
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stateCount[1] = 0;
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stateCount[2] = 0;
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stateCount[3] = 0;
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stateCount[4] = 0;
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}
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else
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{
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// No, shift counts back by two
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stateCount[0] = stateCount[2];
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stateCount[1] = stateCount[3];
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stateCount[2] = stateCount[4];
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stateCount[3] = 1;
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stateCount[4] = 0;
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currentState = 3;
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}
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}
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else
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{
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stateCount[++currentState]++;
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}
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}
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else
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{
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// Counting white pixels
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stateCount[currentState]++;
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}
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}
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}
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if (foundPatternCross(stateCount))
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{
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bool confirmed = handlePossibleCenter(stateCount, i, maxJ);
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if (confirmed)
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{
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iSkip = stateCount[0];
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if (hasSkipped)
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{
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// Found a third one
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done = haveMultiplyConfirmedCenters();
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}
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}
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}
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}
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FinderPattern[] patternInfo = selectBestPatterns();
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ResultPoint.orderBestPatterns(patternInfo);
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return new FinderPatternInfo(patternInfo);
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}
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/// <summary> Given a count of black/white/black/white/black pixels just seen and an end position,
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/// figures the location of the center of this run.
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/// </summary>
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private static float centerFromEnd(int[] stateCount, int end)
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{
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//UPGRADE_WARNING: Data types in Visual C# might be different. Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
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return (float) (end - stateCount[4] - stateCount[3]) - stateCount[2] / 2.0f;
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}
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/// <param name="stateCount">count of black/white/black/white/black pixels just read
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/// </param>
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/// <returns> true iff the proportions of the counts is close enough to the 1/1/3/1/1 ratios
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/// used by finder patterns to be considered a match
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/// </returns>
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protected internal static bool foundPatternCross(int[] stateCount)
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{
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int totalModuleSize = 0;
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for (int i = 0; i < 5; i++)
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{
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int count = stateCount[i];
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if (count == 0)
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{
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return false;
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}
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totalModuleSize += count;
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}
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if (totalModuleSize < 7)
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{
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return false;
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}
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int moduleSize = (totalModuleSize << INTEGER_MATH_SHIFT) / 7;
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int maxVariance = moduleSize / 2;
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// Allow less than 50% variance from 1-1-3-1-1 proportions
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return System.Math.Abs(moduleSize - (stateCount[0] << INTEGER_MATH_SHIFT)) < maxVariance && System.Math.Abs(moduleSize - (stateCount[1] << INTEGER_MATH_SHIFT)) < maxVariance && System.Math.Abs(3 * moduleSize - (stateCount[2] << INTEGER_MATH_SHIFT)) < 3 * maxVariance && System.Math.Abs(moduleSize - (stateCount[3] << INTEGER_MATH_SHIFT)) < maxVariance && System.Math.Abs(moduleSize - (stateCount[4] << INTEGER_MATH_SHIFT)) < maxVariance;
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}
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/// <summary> <p>After a horizontal scan finds a potential finder pattern, this method
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/// "cross-checks" by scanning down vertically through the center of the possible
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/// finder pattern to see if the same proportion is detected.</p>
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///
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/// </summary>
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/// <param name="startI">row where a finder pattern was detected
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/// </param>
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/// <param name="centerJ">center of the section that appears to cross a finder pattern
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/// </param>
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/// <param name="maxCount">maximum reasonable number of modules that should be
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/// observed in any reading state, based on the results of the horizontal scan
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/// </param>
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/// <returns> vertical center of finder pattern, or {@link Float#NaN} if not found
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/// </returns>
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private float crossCheckVertical(int startI, int centerJ, int maxCount, int originalStateCountTotal)
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{
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BitMatrix image = this.image;
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int maxI = image.Height;
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int[] stateCount = CrossCheckStateCount;
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// Start counting up from center
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int i = startI;
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while (i >= 0 && image.get_Renamed(centerJ, i))
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{
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stateCount[2]++;
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i--;
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}
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if (i < 0)
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{
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return System.Single.NaN;
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}
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while (i >= 0 && !image.get_Renamed(centerJ, i) && stateCount[1] <= maxCount)
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{
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stateCount[1]++;
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i--;
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}
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// If already too many modules in this state or ran off the edge:
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if (i < 0 || stateCount[1] > maxCount)
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{
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return System.Single.NaN;
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}
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while (i >= 0 && image.get_Renamed(centerJ, i) && stateCount[0] <= maxCount)
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{
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stateCount[0]++;
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i--;
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}
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if (stateCount[0] > maxCount)
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{
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return System.Single.NaN;
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}
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// Now also count down from center
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i = startI + 1;
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while (i < maxI && image.get_Renamed(centerJ, i))
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{
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stateCount[2]++;
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i++;
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}
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if (i == maxI)
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{
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return System.Single.NaN;
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}
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while (i < maxI && !image.get_Renamed(centerJ, i) && stateCount[3] < maxCount)
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{
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stateCount[3]++;
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i++;
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}
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if (i == maxI || stateCount[3] >= maxCount)
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{
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return System.Single.NaN;
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}
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while (i < maxI && image.get_Renamed(centerJ, i) && stateCount[4] < maxCount)
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{
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stateCount[4]++;
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i++;
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}
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if (stateCount[4] >= maxCount)
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{
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return System.Single.NaN;
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}
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// If we found a finder-pattern-like section, but its size is more than 40% different than
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// the original, assume it's a false positive
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int stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2] + stateCount[3] + stateCount[4];
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if (5 * System.Math.Abs(stateCountTotal - originalStateCountTotal) >= 2 * originalStateCountTotal)
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{
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return System.Single.NaN;
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}
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return foundPatternCross(stateCount)?centerFromEnd(stateCount, i):System.Single.NaN;
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}
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/// <summary> <p>Like {@link #crossCheckVertical(int, int, int, int)}, and in fact is basically identical,
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/// except it reads horizontally instead of vertically. This is used to cross-cross
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/// check a vertical cross check and locate the real center of the alignment pattern.</p>
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/// </summary>
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private float crossCheckHorizontal(int startJ, int centerI, int maxCount, int originalStateCountTotal)
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{
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BitMatrix image = this.image;
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int maxJ = image.Width;
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int[] stateCount = CrossCheckStateCount;
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int j = startJ;
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while (j >= 0 && image.get_Renamed(j, centerI))
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{
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stateCount[2]++;
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j--;
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}
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if (j < 0)
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{
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return System.Single.NaN;
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}
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while (j >= 0 && !image.get_Renamed(j, centerI) && stateCount[1] <= maxCount)
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{
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stateCount[1]++;
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j--;
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}
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if (j < 0 || stateCount[1] > maxCount)
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{
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return System.Single.NaN;
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}
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while (j >= 0 && image.get_Renamed(j, centerI) && stateCount[0] <= maxCount)
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{
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stateCount[0]++;
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j--;
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}
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if (stateCount[0] > maxCount)
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{
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return System.Single.NaN;
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}
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j = startJ + 1;
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while (j < maxJ && image.get_Renamed(j, centerI))
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{
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stateCount[2]++;
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j++;
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}
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if (j == maxJ)
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{
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return System.Single.NaN;
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}
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while (j < maxJ && !image.get_Renamed(j, centerI) && stateCount[3] < maxCount)
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{
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stateCount[3]++;
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j++;
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}
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if (j == maxJ || stateCount[3] >= maxCount)
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{
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return System.Single.NaN;
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}
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while (j < maxJ && image.get_Renamed(j, centerI) && stateCount[4] < maxCount)
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{
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stateCount[4]++;
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j++;
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}
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if (stateCount[4] >= maxCount)
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{
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return System.Single.NaN;
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}
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// If we found a finder-pattern-like section, but its size is significantly different than
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// the original, assume it's a false positive
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int stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2] + stateCount[3] + stateCount[4];
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if (5 * System.Math.Abs(stateCountTotal - originalStateCountTotal) >= originalStateCountTotal)
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{
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return System.Single.NaN;
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}
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return foundPatternCross(stateCount)?centerFromEnd(stateCount, j):System.Single.NaN;
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}
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/// <summary> <p>This is called when a horizontal scan finds a possible alignment pattern. It will
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/// cross check with a vertical scan, and if successful, will, ah, cross-cross-check
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/// with another horizontal scan. This is needed primarily to locate the real horizontal
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/// center of the pattern in cases of extreme skew.</p>
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///
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/// <p>If that succeeds the finder pattern location is added to a list that tracks
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/// the number of times each location has been nearly-matched as a finder pattern.
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/// Each additional find is more evidence that the location is in fact a finder
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/// pattern center
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///
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/// </summary>
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/// <param name="stateCount">reading state module counts from horizontal scan
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/// </param>
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/// <param name="i">row where finder pattern may be found
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/// </param>
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/// <param name="j">end of possible finder pattern in row
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/// </param>
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/// <returns> true if a finder pattern candidate was found this time
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/// </returns>
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protected internal virtual bool handlePossibleCenter(int[] stateCount, int i, int j)
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{
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int stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2] + stateCount[3] + stateCount[4];
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float centerJ = centerFromEnd(stateCount, j);
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//UPGRADE_WARNING: Data types in Visual C# might be different. Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
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float centerI = crossCheckVertical(i, (int) centerJ, stateCount[2], stateCountTotal);
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if (!System.Single.IsNaN(centerI))
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{
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// Re-cross check
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//UPGRADE_WARNING: Data types in Visual C# might be different. Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
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centerJ = crossCheckHorizontal((int) centerJ, (int) centerI, stateCount[2], stateCountTotal);
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if (!System.Single.IsNaN(centerJ))
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{
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//UPGRADE_WARNING: Data types in Visual C# might be different. Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
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float estimatedModuleSize = (float) stateCountTotal / 7.0f;
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bool found = false;
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int max = possibleCenters.Count;
|
|
for (int index = 0; index < max; index++)
|
|
{
|
|
FinderPattern center = (FinderPattern) possibleCenters[index];
|
|
// Look for about the same center and module size:
|
|
if (center.aboutEquals(estimatedModuleSize, centerI, centerJ))
|
|
{
|
|
center.incrementCount();
|
|
found = true;
|
|
break;
|
|
}
|
|
}
|
|
if (!found)
|
|
{
|
|
ResultPoint point = new FinderPattern(centerJ, centerI, estimatedModuleSize);
|
|
possibleCenters.Add(point);
|
|
if (resultPointCallback != null)
|
|
{
|
|
resultPointCallback.foundPossibleResultPoint(point);
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// <returns> number of rows we could safely skip during scanning, based on the first
|
|
/// two finder patterns that have been located. In some cases their position will
|
|
/// allow us to infer that the third pattern must lie below a certain point farther
|
|
/// down in the image.
|
|
/// </returns>
|
|
private int findRowSkip()
|
|
{
|
|
int max = possibleCenters.Count;
|
|
if (max <= 1)
|
|
{
|
|
return 0;
|
|
}
|
|
FinderPattern firstConfirmedCenter = null;
|
|
for (int i = 0; i < max; i++)
|
|
{
|
|
FinderPattern center = (FinderPattern) possibleCenters[i];
|
|
if (center.Count >= CENTER_QUORUM)
|
|
{
|
|
if (firstConfirmedCenter == null)
|
|
{
|
|
firstConfirmedCenter = center;
|
|
}
|
|
else
|
|
{
|
|
// We have two confirmed centers
|
|
// How far down can we skip before resuming looking for the next
|
|
// pattern? In the worst case, only the difference between the
|
|
// difference in the x / y coordinates of the two centers.
|
|
// This is the case where you find top left last.
|
|
hasSkipped = true;
|
|
//UPGRADE_WARNING: Data types in Visual C# might be different. Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
|
|
return (int) (System.Math.Abs(firstConfirmedCenter.X - center.X) - System.Math.Abs(firstConfirmedCenter.Y - center.Y)) / 2;
|
|
}
|
|
}
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/// <returns> true iff we have found at least 3 finder patterns that have been detected
|
|
/// at least {@link #CENTER_QUORUM} times each, and, the estimated module size of the
|
|
/// candidates is "pretty similar"
|
|
/// </returns>
|
|
private bool haveMultiplyConfirmedCenters()
|
|
{
|
|
int confirmedCount = 0;
|
|
float totalModuleSize = 0.0f;
|
|
int max = possibleCenters.Count;
|
|
for (int i = 0; i < max; i++)
|
|
{
|
|
FinderPattern pattern = (FinderPattern) possibleCenters[i];
|
|
if (pattern.Count >= CENTER_QUORUM)
|
|
{
|
|
confirmedCount++;
|
|
totalModuleSize += pattern.EstimatedModuleSize;
|
|
}
|
|
}
|
|
if (confirmedCount < 3)
|
|
{
|
|
return false;
|
|
}
|
|
// OK, we have at least 3 confirmed centers, but, it's possible that one is a "false positive"
|
|
// and that we need to keep looking. We detect this by asking if the estimated module sizes
|
|
// vary too much. We arbitrarily say that when the total deviation from average exceeds
|
|
// 5% of the total module size estimates, it's too much.
|
|
//UPGRADE_WARNING: Data types in Visual C# might be different. Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
|
|
float average = totalModuleSize / (float) max;
|
|
float totalDeviation = 0.0f;
|
|
for (int i = 0; i < max; i++)
|
|
{
|
|
FinderPattern pattern = (FinderPattern) possibleCenters[i];
|
|
totalDeviation += System.Math.Abs(pattern.EstimatedModuleSize - average);
|
|
}
|
|
return totalDeviation <= 0.05f * totalModuleSize;
|
|
}
|
|
|
|
/// <returns> the 3 best {@link FinderPattern}s from our list of candidates. The "best" are
|
|
/// those that have been detected at least {@link #CENTER_QUORUM} times, and whose module
|
|
/// size differs from the average among those patterns the least
|
|
/// </returns>
|
|
/// <throws> ReaderException if 3 such finder patterns do not exist </throws>
|
|
private FinderPattern[] selectBestPatterns()
|
|
{
|
|
|
|
int startSize = possibleCenters.Count;
|
|
if (startSize < 3)
|
|
{
|
|
// Couldn't find enough finder patterns
|
|
throw ReaderException.Instance;
|
|
}
|
|
|
|
// Filter outlier possibilities whose module size is too different
|
|
if (startSize > 3)
|
|
{
|
|
// But we can only afford to do so if we have at least 4 possibilities to choose from
|
|
float totalModuleSize = 0.0f;
|
|
for (int i = 0; i < startSize; i++)
|
|
{
|
|
totalModuleSize += ((FinderPattern) possibleCenters[i]).EstimatedModuleSize;
|
|
}
|
|
//UPGRADE_WARNING: Data types in Visual C# might be different. Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
|
|
float average = totalModuleSize / (float) startSize;
|
|
for (int i = 0; i < possibleCenters.Count && possibleCenters.Count > 3; i++)
|
|
{
|
|
FinderPattern pattern = (FinderPattern) possibleCenters[i];
|
|
if (System.Math.Abs(pattern.EstimatedModuleSize - average) > 0.2f * average)
|
|
{
|
|
possibleCenters.RemoveAt(i);
|
|
i--;
|
|
}
|
|
}
|
|
}
|
|
|
|
if (possibleCenters.Count > 3)
|
|
{
|
|
// Throw away all but those first size candidate points we found.
|
|
Collections.insertionSort(possibleCenters, new CenterComparator());
|
|
SupportClass.SetCapacity(possibleCenters, 3);
|
|
}
|
|
|
|
return new FinderPattern[]{(FinderPattern) possibleCenters[0], (FinderPattern) possibleCenters[1], (FinderPattern) possibleCenters[2]};
|
|
}
|
|
|
|
/// <summary> <p>Orders by {@link FinderPattern#getCount()}, descending.</p></summary>
|
|
private class CenterComparator : Comparator
|
|
{
|
|
public virtual int compare(System.Object center1, System.Object center2)
|
|
{
|
|
return ((FinderPattern) center2).Count - ((FinderPattern) center1).Count;
|
|
}
|
|
}
|
|
}
|
|
} |