mirror of https://github.com/status-im/qzxing.git
542 lines
18 KiB
C++
542 lines
18 KiB
C++
// -*- mode:c++; tab-width:2; indent-tabs-mode:nil; c-basic-offset:2 -*-
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/*
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* FinderPatternFinder.cpp
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* zxing
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*
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* Created by Christian Brunschen on 13/05/2008.
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* Copyright 2008 ZXing authors All rights reserved.
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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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#include <zxing/qrcode/detector/FinderPatternFinder.h>
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#include <zxing/ReaderException.h>
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#include <zxing/DecodeHints.h>
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#include <vector>
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#include <cmath>
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#include <cstdlib>
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#include <algorithm>
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namespace zxing {
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namespace qrcode {
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using namespace std;
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class FurthestFromAverageComparator {
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private:
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const float averageModuleSize_;
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public:
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FurthestFromAverageComparator(float averageModuleSize) :
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averageModuleSize_(averageModuleSize) {
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}
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bool operator()(Ref<FinderPattern> a, Ref<FinderPattern> b) {
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float dA = abs(a->getEstimatedModuleSize() - averageModuleSize_);
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float dB = abs(b->getEstimatedModuleSize() - averageModuleSize_);
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return dA > dB;
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}
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};
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class CenterComparator {
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const float averageModuleSize_;
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public:
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CenterComparator(float averageModuleSize) :
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averageModuleSize_(averageModuleSize) {
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}
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bool operator()(Ref<FinderPattern> a, Ref<FinderPattern> b) {
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// N.B.: we want the result in descending order ...
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if (a->getCount() != b->getCount()) {
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return a->getCount() > b->getCount();
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} else {
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float dA = abs(a->getEstimatedModuleSize() - averageModuleSize_);
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float dB = abs(b->getEstimatedModuleSize() - averageModuleSize_);
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return dA < dB;
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}
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}
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};
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int FinderPatternFinder::CENTER_QUORUM = 2;
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int FinderPatternFinder::MIN_SKIP = 3;
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int FinderPatternFinder::MAX_MODULES = 57;
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float FinderPatternFinder::centerFromEnd(int* stateCount, int end) {
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return (float)(end - stateCount[4] - stateCount[3]) - stateCount[2] / 2.0f;
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}
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bool FinderPatternFinder::foundPatternCross(int* stateCount) {
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int totalModuleSize = 0;
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for (int i = 0; i < 5; i++) {
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if (stateCount[i] == 0) {
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return false;
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}
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totalModuleSize += stateCount[i];
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}
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if (totalModuleSize < 7) {
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return false;
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}
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float moduleSize = (float)totalModuleSize / 7.0f;
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float maxVariance = moduleSize / 2.0f;
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// Allow less than 50% variance from 1-1-3-1-1 proportions
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return abs(moduleSize - stateCount[0]) < maxVariance && abs(moduleSize - stateCount[1]) < maxVariance && abs(3.0f
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* moduleSize - stateCount[2]) < 3.0f * maxVariance && abs(moduleSize - stateCount[3]) < maxVariance && abs(
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moduleSize - stateCount[4]) < maxVariance;
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}
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float FinderPatternFinder::crossCheckVertical(size_t startI, size_t centerJ, int maxCount, int originalStateCountTotal) {
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int maxI = image_->getHeight();
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int stateCount[5];
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for (int i = 0; i < 5; i++)
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stateCount[i] = 0;
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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(centerJ, i)) {
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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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return NAN;
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}
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while (i >= 0 && !image_->get(centerJ, i) && stateCount[1] <= maxCount) {
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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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return NAN;
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}
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while (i >= 0 && image_->get(centerJ, i) && stateCount[0] <= maxCount) {
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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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return 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(centerJ, i)) {
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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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return NAN;
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}
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while (i < maxI && !image_->get(centerJ, i) && stateCount[3] < maxCount) {
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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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return NAN;
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}
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while (i < maxI && image_->get(centerJ, i) && stateCount[4] < maxCount) {
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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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return 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 * abs(stateCountTotal - originalStateCountTotal) >= 2 * originalStateCountTotal) {
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return NAN;
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}
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return foundPatternCross(stateCount) ? centerFromEnd(stateCount, i) : NAN;
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}
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float FinderPatternFinder::crossCheckHorizontal(size_t startJ, size_t centerI, int maxCount,
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int originalStateCountTotal) {
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int maxJ = image_->getWidth();
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int stateCount[5];
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for (int i = 0; i < 5; i++)
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stateCount[i] = 0;
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int j = startJ;
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while (j >= 0 && image_->get(j, centerI)) {
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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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return NAN;
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}
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while (j >= 0 && !image_->get(j, centerI) && stateCount[1] <= maxCount) {
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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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return NAN;
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}
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while (j >= 0 && image_->get(j, centerI) && stateCount[0] <= maxCount) {
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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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return NAN;
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}
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j = startJ + 1;
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while (j < maxJ && image_->get(j, centerI)) {
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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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return NAN;
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}
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while (j < maxJ && !image_->get(j, centerI) && stateCount[3] < maxCount) {
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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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return NAN;
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}
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while (j < maxJ && image_->get(j, centerI) && stateCount[4] < maxCount) {
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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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return 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 * abs(stateCountTotal - originalStateCountTotal) >= originalStateCountTotal) {
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return NAN;
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}
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return foundPatternCross(stateCount) ? centerFromEnd(stateCount, j) : NAN;
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}
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bool FinderPatternFinder::handlePossibleCenter(int* stateCount, size_t i, size_t j) {
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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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float centerI = crossCheckVertical(i, (size_t)centerJ, stateCount[2], stateCountTotal);
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if (!isnan(centerI)) {
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// Re-cross check
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centerJ = crossCheckHorizontal((size_t)centerJ, (size_t)centerI, stateCount[2], stateCountTotal);
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if (!isnan(centerJ)) {
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float estimatedModuleSize = (float)stateCountTotal / 7.0f;
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bool found = false;
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size_t max = possibleCenters_.size();
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for (size_t index = 0; index < max; index++) {
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Ref<FinderPattern> center = possibleCenters_[index];
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// Look for about the same center and module size:
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if (center->aboutEquals(estimatedModuleSize, centerI, centerJ)) {
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possibleCenters_[index] = center->combineEstimate(centerI, centerJ, estimatedModuleSize);
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found = true;
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break;
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}
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}
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if (!found) {
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Ref<FinderPattern> newPattern(new FinderPattern(centerJ, centerI, estimatedModuleSize));
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possibleCenters_.push_back(newPattern);
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if (callback_ != 0) {
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callback_->foundPossibleResultPoint(*newPattern);
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}
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}
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return true;
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}
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}
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return false;
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}
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int FinderPatternFinder::findRowSkip() {
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size_t max = possibleCenters_.size();
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if (max <= 1) {
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return 0;
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}
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Ref<FinderPattern> firstConfirmedCenter;
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for (size_t i = 0; i < max; i++) {
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Ref<FinderPattern> center = possibleCenters_[i];
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if (center->getCount() >= CENTER_QUORUM) {
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if (firstConfirmedCenter == 0) {
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firstConfirmedCenter = center;
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} else {
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// We have two confirmed centers
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// How far down can we skip before resuming looking for the next
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// pattern? In the worst case, only the difference between the
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// difference in the x / y coordinates of the two centers.
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// This is the case where you find top left first. Draw it out.
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hasSkipped_ = true;
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return (int)(abs(firstConfirmedCenter->getX() - center->getX()) - abs(firstConfirmedCenter->getY()
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- center->getY()))/2;
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}
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}
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}
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return 0;
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}
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bool FinderPatternFinder::haveMultiplyConfirmedCenters() {
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int confirmedCount = 0;
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float totalModuleSize = 0.0f;
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size_t max = possibleCenters_.size();
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for (size_t i = 0; i < max; i++) {
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Ref<FinderPattern> pattern = possibleCenters_[i];
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if (pattern->getCount() >= CENTER_QUORUM) {
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confirmedCount++;
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totalModuleSize += pattern->getEstimatedModuleSize();
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}
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}
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if (confirmedCount < 3) {
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return false;
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}
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// OK, we have at least 3 confirmed centers, but, it's possible that one is a "false positive"
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// and that we need to keep looking. We detect this by asking if the estimated module sizes
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// vary too much. We arbitrarily say that when the total deviation from average exceeds
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// 5% of the total module size estimates, it's too much.
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float average = totalModuleSize / max;
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float totalDeviation = 0.0f;
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for (size_t i = 0; i < max; i++) {
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Ref<FinderPattern> pattern = possibleCenters_[i];
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totalDeviation += abs(pattern->getEstimatedModuleSize() - average);
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}
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return totalDeviation <= 0.05f * totalModuleSize;
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}
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vector<Ref<FinderPattern> > FinderPatternFinder::selectBestPatterns() {
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size_t startSize = possibleCenters_.size();
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if (startSize < 3) {
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// Couldn't find enough finder patterns
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throw zxing::ReaderException("Could not find three finder patterns");
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}
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// Filter outlier possibilities whose module size is too different
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if (startSize > 3) {
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// But we can only afford to do so if we have at least 4 possibilities to choose from
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float totalModuleSize = 0.0f;
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float square = 0.0f;
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for (size_t i = 0; i < startSize; i++) {
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float size = possibleCenters_[i]->getEstimatedModuleSize();
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totalModuleSize += size;
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square += size * size;
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}
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float average = totalModuleSize / (float) startSize;
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float stdDev = (float)sqrt(square / startSize - average * average);
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sort(possibleCenters_.begin(), possibleCenters_.end(), FurthestFromAverageComparator(average));
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float limit = max(0.2f * average, stdDev);
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for (size_t i = 0; i < possibleCenters_.size() && possibleCenters_.size() > 3; i++) {
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if (abs(possibleCenters_[i]->getEstimatedModuleSize() - average) > limit) {
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possibleCenters_.erase(possibleCenters_.begin()+i);
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i--;
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}
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}
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}
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if (possibleCenters_.size() > 3) {
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// Throw away all but those first size candidate points we found.
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float totalModuleSize = 0.0f;
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for (size_t i = 0; i < possibleCenters_.size(); i++) {
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float size = possibleCenters_[i]->getEstimatedModuleSize();
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totalModuleSize += size;
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}
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float average = totalModuleSize / (float) possibleCenters_.size();
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sort(possibleCenters_.begin(), possibleCenters_.end(), CenterComparator(average));
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}
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if (possibleCenters_.size() > 3) {
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possibleCenters_.erase(possibleCenters_.begin()+3,possibleCenters_.end());
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}
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vector<Ref<FinderPattern> > result(3);
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result[0] = possibleCenters_[0];
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result[1] = possibleCenters_[1];
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result[2] = possibleCenters_[2];
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return result;
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}
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vector<Ref<FinderPattern> > FinderPatternFinder::orderBestPatterns(vector<Ref<FinderPattern> > patterns) {
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// Find distances between pattern centers
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float abDistance = distance(patterns[0], patterns[1]);
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float bcDistance = distance(patterns[1], patterns[2]);
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float acDistance = distance(patterns[0], patterns[2]);
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Ref<FinderPattern> topLeft;
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Ref<FinderPattern> topRight;
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Ref<FinderPattern> bottomLeft;
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// Assume one closest to other two is top left;
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// topRight and bottomLeft will just be guesses below at first
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if (bcDistance >= abDistance && bcDistance >= acDistance) {
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topLeft = patterns[0];
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topRight = patterns[1];
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bottomLeft = patterns[2];
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} else if (acDistance >= bcDistance && acDistance >= abDistance) {
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topLeft = patterns[1];
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topRight = patterns[0];
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bottomLeft = patterns[2];
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} else {
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topLeft = patterns[2];
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topRight = patterns[0];
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bottomLeft = patterns[1];
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}
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// Use cross product to figure out which of other1/2 is the bottom left
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// pattern. The vector "top-left -> bottom-left" x "top-left -> top-right"
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// should yield a vector with positive z component
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if ((bottomLeft->getY() - topLeft->getY()) * (topRight->getX() - topLeft->getX()) < (bottomLeft->getX()
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- topLeft->getX()) * (topRight->getY() - topLeft->getY())) {
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Ref<FinderPattern> temp = topRight;
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topRight = bottomLeft;
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bottomLeft = temp;
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}
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vector<Ref<FinderPattern> > results(3);
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results[0] = bottomLeft;
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results[1] = topLeft;
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results[2] = topRight;
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return results;
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}
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float FinderPatternFinder::distance(Ref<ResultPoint> p1, Ref<ResultPoint> p2) {
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float dx = p1->getX() - p2->getX();
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float dy = p1->getY() - p2->getY();
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return (float)sqrt(dx * dx + dy * dy);
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}
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FinderPatternFinder::FinderPatternFinder(Ref<BitMatrix> image,
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Ref<ResultPointCallback>const& callback) :
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image_(image), possibleCenters_(), hasSkipped_(false), callback_(callback) {
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}
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Ref<FinderPatternInfo> FinderPatternFinder::find(DecodeHints const& hints) {
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bool tryHarder = hints.getTryHarder();
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size_t maxI = image_->getHeight();
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size_t maxJ = image_->getWidth();
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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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// As this is used often, we use an integer array instead of vector
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int stateCount[5];
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bool done = false;
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// Let's assume that the maximum version QR Code we support takes up 1/4
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// the height of the image, and then account for the center being 3
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// modules in size. This gives the smallest number of pixels the center
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// 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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iSkip = MIN_SKIP;
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}
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// This is slightly faster than using the Ref. Efficiency is important here
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BitMatrix& matrix = *image_;
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for (size_t i = iSkip - 1; i < maxI && !done; i += iSkip) {
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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 (size_t j = 0; j < maxJ; j++) {
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if (matrix.get(j, i)) {
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// Black pixel
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if ((currentState & 1) == 1) { // Counting white pixels
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currentState++;
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}
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stateCount[currentState]++;
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} else { // White pixel
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if ((currentState & 1) == 0) { // Counting black pixels
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if (currentState == 4) { // A winner?
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if (foundPatternCross(stateCount)) { // Yes
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bool confirmed = handlePossibleCenter(stateCount, i, j);
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if (confirmed) {
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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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done = haveMultiplyConfirmedCenters();
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} else {
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int rowSkip = findRowSkip();
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if (rowSkip > stateCount[2]) {
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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
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// of last center of pattern we saw) to be conservative,
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// and also back off by iSkip which is about to be
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// re-added
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i += rowSkip - stateCount[2] - iSkip;
|
|
j = maxJ - 1;
|
|
}
|
|
}
|
|
} else {
|
|
stateCount[0] = stateCount[2];
|
|
stateCount[1] = stateCount[3];
|
|
stateCount[2] = stateCount[4];
|
|
stateCount[3] = 1;
|
|
stateCount[4] = 0;
|
|
currentState = 3;
|
|
continue;
|
|
}
|
|
// Clear state to start looking again
|
|
currentState = 0;
|
|
stateCount[0] = 0;
|
|
stateCount[1] = 0;
|
|
stateCount[2] = 0;
|
|
stateCount[3] = 0;
|
|
stateCount[4] = 0;
|
|
} else { // No, shift counts back by two
|
|
stateCount[0] = stateCount[2];
|
|
stateCount[1] = stateCount[3];
|
|
stateCount[2] = stateCount[4];
|
|
stateCount[3] = 1;
|
|
stateCount[4] = 0;
|
|
currentState = 3;
|
|
}
|
|
} else {
|
|
stateCount[++currentState]++;
|
|
}
|
|
} else { // Counting white pixels
|
|
stateCount[currentState]++;
|
|
}
|
|
}
|
|
}
|
|
if (foundPatternCross(stateCount)) {
|
|
bool confirmed = handlePossibleCenter(stateCount, i, maxJ);
|
|
if (confirmed) {
|
|
iSkip = stateCount[0];
|
|
if (hasSkipped_) {
|
|
// Found a third one
|
|
done = haveMultiplyConfirmedCenters();
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
vector<Ref<FinderPattern> > patternInfo = selectBestPatterns();
|
|
patternInfo = orderBestPatterns(patternInfo);
|
|
|
|
Ref<FinderPatternInfo> result(new FinderPatternInfo(patternInfo));
|
|
return result;
|
|
}
|
|
}
|
|
}
|