--- /dev/null
+/*
+ * FinderPatternFinder.cpp
+ * zxing
+ *
+ * Created by Christian Brunschen on 13/05/2008.
+ * Copyright 2008 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "FinderPatternFinder.h"
+#include "../../ReaderException.h"
+#include <vector>
+#include <cmath>
+
+namespace qrcode {
+ namespace detector {
+
+ using namespace std;
+ using namespace common;
+
+ class ClosestToAverageComparator {
+ private:
+ float averageModuleSize_;
+ public:
+ ClosestToAverageComparator(float averageModuleSize) :
+ averageModuleSize_(averageModuleSize) { }
+ int operator()(Ref<FinderPattern> a, Ref<FinderPattern> b) {
+ float dA = abs(a->getEstimatedModuleSize() - averageModuleSize_);
+ float dB = abs(b->getEstimatedModuleSize() - averageModuleSize_);
+ return dA < dB ? -1 : dA > dB ? 1 : 0;
+ }
+ };
+
+ class CenterComparator {
+ public:
+ int operator()(Ref<FinderPattern> a, Ref<FinderPattern> b) {
+ return b->getCount() - a->getCount();
+ }
+ };
+
+ int FinderPatternFinder::CENTER_QUORUM = 2;
+ int FinderPatternFinder::MIN_SKIP = 3;
+ int FinderPatternFinder::MAX_MODULES = 57;
+
+ float FinderPatternFinder::centerFromEnd(valarray<int> &stateCount,
+ int end) {
+ return (float) (end - stateCount[4] - stateCount[3]) -
+ stateCount[2] / 2.0f;
+ }
+
+ bool FinderPatternFinder::foundPatternCross(valarray<int> &stateCount) {
+ int totalModuleSize = 0;
+ for (int i = 0; i < 5; i++) {
+ if (stateCount[i] == 0) {
+ return false;
+ }
+ totalModuleSize += stateCount[i];
+ }
+ if (totalModuleSize < 7) {
+ return false;
+ }
+ float moduleSize = (float) totalModuleSize / 7.0f;
+ float maxVariance = moduleSize / 2.0f;
+ // Allow less than 50% variance from 1-1-3-1-1 proportions
+ return abs(moduleSize - stateCount[0]) < maxVariance &&
+ abs(moduleSize - stateCount[1]) < maxVariance &&
+ abs(3.0f * moduleSize - stateCount[2]) < 3.0f * maxVariance &&
+ abs(moduleSize - stateCount[3]) < maxVariance &&
+ abs(moduleSize - stateCount[4]) < maxVariance;
+ }
+
+ float FinderPatternFinder::crossCheckVertical(size_t startI, size_t centerJ,
+ int maxCount,
+ int originalStateCountTotal) {
+
+ int maxI = image_->getHeight();
+ valarray<int> stateCount(5);
+
+ // Start counting up from center
+ int i = startI;
+ while (i >= 0 && image_->isBlack(centerJ, i)) {
+ stateCount[2]++;
+ i--;
+ }
+ if (i < 0) {
+ return NAN;
+ }
+ while (i >= 0 && !image_->isBlack(centerJ, i) && stateCount[1] <= maxCount) {
+ stateCount[1]++;
+ i--;
+ }
+ // If already too many modules in this state or ran off the edge:
+ if (i < 0 || stateCount[1] > maxCount) {
+ return NAN;
+ }
+ while (i >= 0 && image_->isBlack(centerJ, i) && stateCount[0] <= maxCount) {
+ stateCount[0]++;
+ i--;
+ }
+ if (stateCount[0] > maxCount) {
+ return NAN;
+ }
+
+ // Now also count down from center
+ i = startI + 1;
+ while (i < maxI && image_->isBlack(centerJ, i)) {
+ stateCount[2]++;
+ i++;
+ }
+ if (i == maxI) {
+ return NAN;
+ }
+ while (i < maxI && !image_->isBlack(centerJ, i) && stateCount[3] < maxCount) {
+ stateCount[3]++;
+ i++;
+ }
+ if (i == maxI || stateCount[3] >= maxCount) {
+ return NAN;
+ }
+ while (i < maxI && image_->isBlack(centerJ, i) && stateCount[4] < maxCount) {
+ stateCount[4]++;
+ i++;
+ }
+ if (stateCount[4] >= maxCount) {
+ return NAN;
+ }
+
+ // If we found a finder-pattern-like section, but its size is more than 20% different than
+ // the original, assume it's a false positive
+ int stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2] + stateCount[3] + stateCount[4];
+ if (5 * abs(stateCountTotal - originalStateCountTotal) >= originalStateCountTotal) {
+ return NAN;
+ }
+
+ return foundPatternCross(stateCount) ? centerFromEnd(stateCount, i) : NAN;
+ }
+
+ float FinderPatternFinder::crossCheckHorizontal(size_t startJ, size_t centerI,
+ int maxCount,
+ int originalStateCountTotal)
+ {
+
+ int maxJ = image_->getWidth();
+ valarray<int> stateCount(5);
+
+ int j = startJ;
+ while (j >= 0 && image_->isBlack(j, centerI)) {
+ stateCount[2]++;
+ j--;
+ }
+ if (j < 0) {
+ return NAN;
+ }
+ while (j >= 0 && !image_->isBlack(j, centerI) &&
+ stateCount[1] <= maxCount) {
+ stateCount[1]++;
+ j--;
+ }
+ if (j < 0 || stateCount[1] > maxCount) {
+ return NAN;
+ }
+ while (j >= 0 && image_->isBlack(j, centerI) &&
+ stateCount[0] <= maxCount) {
+ stateCount[0]++;
+ j--;
+ }
+ if (stateCount[0] > maxCount) {
+ return NAN;
+ }
+
+ j = startJ + 1;
+ while (j < maxJ && image_->isBlack(j, centerI)) {
+ stateCount[2]++;
+ j++;
+ }
+ if (j == maxJ) {
+ return NAN;
+ }
+ while (j < maxJ && !image_->isBlack(j, centerI) &&
+ stateCount[3] < maxCount) {
+ stateCount[3]++;
+ j++;
+ }
+ if (j == maxJ || stateCount[3] >= maxCount) {
+ return NAN;
+ }
+ while (j < maxJ && image_->isBlack(j, centerI) && stateCount[4] < maxCount) {
+ stateCount[4]++;
+ j++;
+ }
+ if (stateCount[4] >= maxCount) {
+ return NAN;
+ }
+
+ // If we found a finder-pattern-like section, but its size is significantly different than
+ // the original, assume it's a false positive
+ int stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2] +
+ stateCount[3] + stateCount[4];
+ if (5 * abs(stateCountTotal - originalStateCountTotal) >=
+ originalStateCountTotal) {
+ return NAN;
+ }
+
+ return foundPatternCross(stateCount) ? centerFromEnd(stateCount, j) : NAN;
+ }
+
+ bool FinderPatternFinder::handlePossibleCenter(valarray<int> &stateCount,
+ size_t i, size_t j) {
+ int stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2] +
+ stateCount[3] + stateCount[4];
+ float centerJ = centerFromEnd(stateCount, j);
+ float centerI = crossCheckVertical(i, centerJ, stateCount[2],
+ stateCountTotal);
+ if (!isnan(centerI)) {
+ // Re-cross check
+ centerJ = crossCheckHorizontal(centerJ, centerI, stateCount[2],
+ stateCountTotal);
+ if (!isnan(centerJ)) {
+ float estimatedModuleSize = (float) stateCountTotal / 7.0f;
+ bool found = false;
+ size_t max = possibleCenters_.size();
+ for (size_t index = 0; index < max; index++) {
+ Ref<FinderPattern> center = possibleCenters_[index];
+ // Look for about the same center and module size:
+ if (center->aboutEquals(estimatedModuleSize, centerI, centerJ)) {
+ center->incrementCount();
+ found = true;
+ break;
+ }
+ }
+ if (!found) {
+ Ref<FinderPattern> newPattern
+ (new FinderPattern(centerJ, centerI,
+ estimatedModuleSize));
+ possibleCenters_.push_back(newPattern);
+ }
+ return true;
+ }
+ }
+ return false;
+ }
+
+ int FinderPatternFinder::findRowSkip() {
+ size_t max = possibleCenters_.size();
+ if (max <= 1) {
+ return 0;
+ }
+ Ref<FinderPattern> firstConfirmedCenter;
+ for (size_t i = 0; i < max; i++) {
+ Ref<FinderPattern> center = possibleCenters_[i];
+ if (center->getCount() >= CENTER_QUORUM) {
+ if (firstConfirmedCenter == 0) {
+ 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 first. Draw it out.
+ hasSkipped_ = true;
+ return (int) abs(abs(firstConfirmedCenter->getX() - center->getX()) -
+ abs(firstConfirmedCenter->getY() - center->getY()));
+ }
+ }
+ }
+ return 0;
+ }
+
+ bool FinderPatternFinder::haveMultiplyConfirmedCenters() {
+ int confirmedCount = 0;
+ float totalModuleSize = 0.0f;
+ size_t max = possibleCenters_.size();
+ for (size_t i = 0; i < max; i++) {
+ Ref<FinderPattern> pattern = possibleCenters_[i];
+ if (pattern->getCount() >= CENTER_QUORUM) {
+ confirmedCount++;
+ totalModuleSize += pattern->getEstimatedModuleSize();
+ }
+ }
+ 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
+ // 15% of the total module size estimates, it's too much.
+ float average = totalModuleSize / max;
+ float totalDeviation = 0.0f;
+ for (size_t i = 0; i < max; i++) {
+ Ref<FinderPattern> pattern = possibleCenters_[i];
+ totalDeviation += abs(pattern->getEstimatedModuleSize() - average);
+ }
+ return totalDeviation <= 0.15f * totalModuleSize;
+ }
+
+ ArrayRef<Ref<FinderPattern> > FinderPatternFinder::selectBestPatterns() {
+ sort(possibleCenters_.begin(), possibleCenters_.end(),
+ CenterComparator());
+ size_t size = 0;
+ size_t max = possibleCenters_.size();
+ while (size < max) {
+ if (possibleCenters_[size]->getCount() < CENTER_QUORUM) {
+ break;
+ }
+ size++;
+ }
+
+ if (size < 3) {
+ // Couldn't find enough finder patterns
+ throw new ReaderException("Could not find three finder patterns");
+ }
+
+ if (size == 3) {
+ // Found just enough -- hope these are good!
+ Ref<FinderPattern> rawResult[] = {
+ possibleCenters_[0], possibleCenters_[1], possibleCenters_[2]
+ };
+ ArrayRef<Ref<FinderPattern> > result(rawResult, 3);
+ return result;
+ }
+
+ // Hmm, multiple found. We need to pick the best three. Find the most
+ // popular ones whose module size is nearest the average
+ float averageModuleSize = 0.0f;
+ for (size_t i = 0; i < size; i++) {
+ averageModuleSize += possibleCenters_[i]->getEstimatedModuleSize();
+ }
+ averageModuleSize /= (float) size;
+
+ sort(possibleCenters_.begin(), possibleCenters_.end(),
+ ClosestToAverageComparator(averageModuleSize));
+
+ Ref<FinderPattern> rawResult[] = {
+ possibleCenters_[0], possibleCenters_[1], possibleCenters_[2]
+ };
+ ArrayRef<Ref<FinderPattern> > result(rawResult, 3);
+ return result;
+ }
+
+ ArrayRef<Ref<FinderPattern> > FinderPatternFinder::orderBestPatterns
+ (ArrayRef<Ref<FinderPattern> > patterns) {
+ // Find distances between pattern centers
+ float abDistance = distance(patterns[0], patterns[1]);
+ float bcDistance = distance(patterns[1], patterns[2]);
+ float acDistance = distance(patterns[0], patterns[2]);
+
+ Ref<FinderPattern> topLeft;
+ Ref<FinderPattern> topRight;
+ Ref<FinderPattern> bottomLeft;
+ // Assume one closest to other two is top left;
+ // topRight and bottomLeft will just be guesses below at first
+ if (bcDistance >= abDistance && bcDistance >= acDistance) {
+ topLeft = patterns[0];
+ topRight = patterns[1];
+ bottomLeft = patterns[2];
+ } else if (acDistance >= bcDistance && acDistance >= abDistance) {
+ topLeft = patterns[1];
+ topRight = patterns[0];
+ bottomLeft = patterns[2];
+ } else {
+ topLeft = patterns[2];
+ topRight = patterns[0];
+ bottomLeft = patterns[1];
+ }
+
+ // Use cross product to figure out which of other1/2 is the bottom left
+ // pattern. The vector "top-left -> bottom-left" x "top-left -> top-right"
+ // should yield a vector with positive z component
+ if ((bottomLeft->getY() - topLeft->getY()) *
+ (topRight->getX() - topLeft->getX()) <
+ (bottomLeft->getX() - topLeft->getX()) *
+ (topRight->getY() - topLeft->getY())) {
+ Ref<FinderPattern> temp = topRight;
+ topRight = bottomLeft;
+ bottomLeft = temp;
+ }
+
+ ArrayRef<Ref<FinderPattern> > results(3);
+ results[0] = bottomLeft;
+ results[1] = topLeft;
+ results[2] = topRight;
+ return results;
+ }
+
+ float FinderPatternFinder::distance(Ref<ResultPoint> p1,
+ Ref<ResultPoint> p2) {
+ float dx = p1->getX() - p2->getX();
+ float dy = p1->getY() - p2->getY();
+ return (float)sqrt(dx*dx + dy*dy);
+ }
+
+ FinderPatternFinder::FinderPatternFinder(Ref<MonochromeBitmapSource> image)
+ : image_(image), possibleCenters_(), hasSkipped_(false) {
+ }
+
+ Ref<FinderPatternInfo> FinderPatternFinder::find() {
+ size_t maxI = image_->getHeight();
+ size_t maxJ = image_->getWidth();
+
+ // We are looking for black/white/black/white/black modules in
+ // 1:1:3:1:1 ratio; this tracks the number of such modules seen so far
+ valarray<int> stateCount(5);
+ bool done = false;
+
+ // Let's assume that the maximum version QR Code we support takes up 1/4
+ // the height of the image, and then account for the center being 3
+ // modules in size. This gives the smallest number of pixels the center
+ // could be, so skip this often. When trying harder, look for all
+ // QR versions regardless of how dense they are.
+ size_t iSkip = MIN_SKIP;
+
+ for (size_t i = iSkip - 1; i < maxI && !done; i += iSkip) {
+ // Get a row of black/white values
+ Ref<BitArray> null;
+ Ref<BitArray> blackRow = image_->getBlackRow(i, null, 0, maxJ);
+ stateCount[0] = 0;
+ stateCount[1] = 0;
+ stateCount[2] = 0;
+ stateCount[3] = 0;
+ stateCount[4] = 0;
+ int currentState = 0;
+ for (size_t j = 0; j < maxJ; j++) {
+ if (blackRow->get(j)) {
+ // Black pixel
+ if ((currentState & 1) == 1) { // Counting white pixels
+ currentState++;
+ }
+ stateCount[currentState]++;
+ } else { // White pixel
+ if ((currentState & 1) == 0) { // Counting black pixels
+ if (currentState == 4) { // A winner?
+ if (foundPatternCross(stateCount)) { // Yes
+ bool confirmed = handlePossibleCenter(stateCount, i, j);
+ if (confirmed) {
+ iSkip = 1; // Go back to examining each line
+ if (hasSkipped_) {
+ done = haveMultiplyConfirmedCenters();
+ } else {
+ int rowSkip = findRowSkip();
+ if (rowSkip > stateCount[2]) {
+ // Skip rows between row of lower confirmed center
+ // and top of presumed third confirmed center
+ // but back up a bit to get a full chance of detecting
+ // it, entire width of center of finder pattern
+
+ // Skip by rowSkip, but back off by stateCount[2] (size
+ // of last center of pattern we saw) to be conservative,
+ // and also back off by iSkip which is about to be
+ // re-added
+ i += rowSkip - stateCount[2] - iSkip;
+ j = maxJ - 1;
+ }
+ }
+ } else {
+ // Advance to next black pixel
+ do {
+ j++;
+ } while (j < maxJ && !blackRow->get(j));
+ j--; // back up to that last white pixel
+ }
+ // 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();
+ }
+ }
+ }
+ }
+
+ ArrayRef<Ref<FinderPattern> > patternInfo = selectBestPatterns();
+ patternInfo = orderBestPatterns(patternInfo);
+
+ Ref<FinderPatternInfo> result(new FinderPatternInfo(patternInfo));
+ return result;
+ }
+ }
+}
projects / zxing.git / blobdiff