QRDetector.cpp Example File

 // -*- mode:c++; tab-width:2; indent-tabs-mode:nil; c-basic-offset:2 -*-
 /*
  *  Detector.cpp
  *  zxing
  *
  *  Created by Christian Brunschen on 14/05/2008.
  *  Copyright 2008 ZXing authors 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 <zxing/qrcode/detector/Detector.h>
 #include <zxing/qrcode/detector/FinderPatternFinder.h>
 #include <zxing/qrcode/detector/FinderPattern.h>
 #include <zxing/qrcode/detector/AlignmentPattern.h>
 #include <zxing/qrcode/detector/AlignmentPatternFinder.h>
 #include <zxing/qrcode/Version.h>
 #include <zxing/common/GridSampler.h>
 #include <zxing/DecodeHints.h>
 #include <zxing/common/detector/MathUtils.h>
 #include <sstream>
 #include <cstdlib>
 #include <algorithm>

 using std::ostringstream;
 using std::abs;
 using std::min;
 using std::max;
 using zxing::qrcode::Detector;
 using zxing::Ref;
 using zxing::BitMatrix;
 using zxing::ResultPointCallback;
 using zxing::DetectorResult;
 using zxing::PerspectiveTransform;
 using zxing::qrcode::AlignmentPattern;
 using zxing::common::detector::MathUtils;

 // VC++
 using zxing::DecodeHints;
 using zxing::qrcode::FinderPatternFinder;
 using zxing::qrcode::FinderPatternInfo;
 using zxing::ResultPoint;

 Detector::Detector(Ref<BitMatrix> image) :
   image_(image) {
 }

 Ref<BitMatrix> Detector::getImage() const {
   return image_;
 }

 Ref<ResultPointCallback> Detector::getResultPointCallback() const {
   return callback_;
 }

 Ref<DetectorResult> Detector::detect(DecodeHints const& hints) {
   callback_ = hints.getResultPointCallback();
   FinderPatternFinder finder(image_, hints.getResultPointCallback());
   Ref<FinderPatternInfo> info(finder.find(hints));
   return processFinderPatternInfo(info);
 }

 Ref<DetectorResult> Detector::processFinderPatternInfo(Ref<FinderPatternInfo> info){
   Ref<FinderPattern> topLeft(info->getTopLeft());
   Ref<FinderPattern> topRight(info->getTopRight());
   Ref<FinderPattern> bottomLeft(info->getBottomLeft());

   float moduleSize = calculateModuleSize(topLeft, topRight, bottomLeft);
   if (moduleSize < 1.0f) {
     throw zxing::ReaderException("bad module size");
   }
   int dimension = computeDimension(topLeft, topRight, bottomLeft, moduleSize);
   Version *provisionalVersion = Version::getProvisionalVersionForDimension(dimension);
   int modulesBetweenFPCenters = provisionalVersion->getDimensionForVersion() - 7;

   Ref<AlignmentPattern> alignmentPattern;
   // Anything above version 1 has an alignment pattern
   if (provisionalVersion->getAlignmentPatternCenters().size() > 0) {

     // Guess where a "bottom right" finder pattern would have been
     float bottomRightX = topRight->getX() - topLeft->getX() + bottomLeft->getX();
     float bottomRightY = topRight->getY() - topLeft->getY() + bottomLeft->getY();

     // Estimate that alignment pattern is closer by 3 modules
     // from "bottom right" to known top left location
     float correctionToTopLeft = 1.0f - 3.0f / (float)modulesBetweenFPCenters;
     int estAlignmentX = (int)(topLeft->getX() + correctionToTopLeft * (bottomRightX - topLeft->getX()));
     int estAlignmentY = (int)(topLeft->getY() + correctionToTopLeft * (bottomRightY - topLeft->getY()));

     // Kind of arbitrary -- expand search radius before giving up
     for (int i = 4; i <= 16; i <<= 1) {
       try {
         alignmentPattern = findAlignmentInRegion(moduleSize, estAlignmentX, estAlignmentY, (float)i);
         break;
       } catch (zxing::ReaderException const& re) {
         (void)re;
         // try next round
       }
     }
     if (alignmentPattern == 0) {
       // Try anyway
     }

   }

   Ref<PerspectiveTransform> transform = createTransform(topLeft, topRight, bottomLeft, alignmentPattern, dimension);
   Ref<BitMatrix> bits(sampleGrid(image_, dimension, transform));
   ArrayRef< Ref<ResultPoint> > points(new Array< Ref<ResultPoint> >(alignmentPattern == 0 ? 3 : 4));
   points[0].reset(bottomLeft);
   points[1].reset(topLeft);
   points[2].reset(topRight);
   if (alignmentPattern != 0) {
     points[3].reset(alignmentPattern);
   }

   Ref<DetectorResult> result(new DetectorResult(bits, points));
   return result;
 }

 Ref<PerspectiveTransform> Detector::createTransform(Ref<ResultPoint> topLeft, Ref<ResultPoint> topRight, Ref <
                                                     ResultPoint > bottomLeft, Ref<ResultPoint> alignmentPattern, int dimension) {

   float dimMinusThree = (float)dimension - 3.5f;
   float bottomRightX;
   float bottomRightY;
   float sourceBottomRightX;
   float sourceBottomRightY;
   if (alignmentPattern != 0) {
     bottomRightX = alignmentPattern->getX();
     bottomRightY = alignmentPattern->getY();
     sourceBottomRightX = dimMinusThree - 3.0f;
     sourceBottomRightY = sourceBottomRightX;
   } else {
     // Don't have an alignment pattern, just make up the bottom-right point
     bottomRightX = (topRight->getX() - topLeft->getX()) + bottomLeft->getX();
     bottomRightY = (topRight->getY() - topLeft->getY()) + bottomLeft->getY();
     sourceBottomRightX = dimMinusThree;
     sourceBottomRightY = dimMinusThree;
   }

   Ref<PerspectiveTransform> transform(PerspectiveTransform::quadrilateralToQuadrilateral(3.5f, 3.5f, dimMinusThree, 3.5f, sourceBottomRightX,
                                                                                          sourceBottomRightY, 3.5f, dimMinusThree, topLeft->getX(), topLeft->getY(), topRight->getX(),
                                                                                          topRight->getY(), bottomRightX, bottomRightY, bottomLeft->getX(), bottomLeft->getY()));

   return transform;
 }

 Ref<BitMatrix> Detector::sampleGrid(Ref<BitMatrix> image, int dimension, Ref<PerspectiveTransform> transform) {
   GridSampler &sampler = GridSampler::getInstance();
   return sampler.sampleGrid(image, dimension, transform);
 }

 int Detector::computeDimension(Ref<ResultPoint> topLeft, Ref<ResultPoint> topRight, Ref<ResultPoint> bottomLeft,
                                float moduleSize) {
   int tltrCentersDimension =
     MathUtils::round(ResultPoint::distance(topLeft, topRight) / moduleSize);
   int tlblCentersDimension =
     MathUtils::round(ResultPoint::distance(topLeft, bottomLeft) / moduleSize);
   int dimension = ((tltrCentersDimension + tlblCentersDimension) >> 1) + 7;
   switch (dimension & 0x03) { // mod 4
   case 0:
     dimension++;
     break;
     // 1? do nothing
   case 2:
     dimension--;
     break;
   case 3:
     ostringstream s;
     s << "Bad dimension: " << dimension;
     throw zxing::ReaderException(s.str().c_str());
   }
   return dimension;
 }

 float Detector::calculateModuleSize(Ref<ResultPoint> topLeft, Ref<ResultPoint> topRight, Ref<ResultPoint> bottomLeft) {
   // Take the average
   return (calculateModuleSizeOneWay(topLeft, topRight) + calculateModuleSizeOneWay(topLeft, bottomLeft)) / 2.0f;
 }

 float Detector::calculateModuleSizeOneWay(Ref<ResultPoint> pattern, Ref<ResultPoint> otherPattern) {
   float moduleSizeEst1 = sizeOfBlackWhiteBlackRunBothWays((int)pattern->getX(), (int)pattern->getY(),
                                                           (int)otherPattern->getX(), (int)otherPattern->getY());
   float moduleSizeEst2 = sizeOfBlackWhiteBlackRunBothWays((int)otherPattern->getX(), (int)otherPattern->getY(),
                                                           (int)pattern->getX(), (int)pattern->getY());
   if (zxing::isnan_z(moduleSizeEst1)) {
     return moduleSizeEst2;
   }
   if (zxing::isnan_z(moduleSizeEst2)) {
     return moduleSizeEst1;
   }
   // Average them, and divide by 7 since we've counted the width of 3 black modules,
   // and 1 white and 1 black module on either side. Ergo, divide sum by 14.
   return (moduleSizeEst1 + moduleSizeEst2) / 14.0f;
 }

 float Detector::sizeOfBlackWhiteBlackRunBothWays(int fromX, int fromY, int toX, int toY) {

   float result = sizeOfBlackWhiteBlackRun(fromX, fromY, toX, toY);

   // Now count other way -- don't run off image though of course
   float scale = 1.0f;
   int otherToX = fromX - (toX - fromX);
   if (otherToX < 0) {
     scale = (float) fromX / (float) (fromX - otherToX);
     otherToX = 0;
   } else if (otherToX >= (int)image_->getWidth()) {
     scale = (float) (image_->getWidth() - 1 - fromX) / (float) (otherToX - fromX);
     otherToX = image_->getWidth() - 1;
   }
   int otherToY = (int) (fromY - (toY - fromY) * scale);

   scale = 1.0f;
   if (otherToY < 0) {
     scale = (float) fromY / (float) (fromY - otherToY);
     otherToY = 0;
   } else if (otherToY >= (int)image_->getHeight()) {
     scale = (float) (image_->getHeight() - 1 - fromY) / (float) (otherToY - fromY);
     otherToY = image_->getHeight() - 1;
   }
   otherToX = (int) (fromX + (otherToX - fromX) * scale);

   result += sizeOfBlackWhiteBlackRun(fromX, fromY, otherToX, otherToY);

   // Middle pixel is double-counted this way; subtract 1
   return result - 1.0f;
 }

 float Detector::sizeOfBlackWhiteBlackRun(int fromX, int fromY, int toX, int toY) {
   // Mild variant of Bresenham's algorithm;
   // see http://en.wikipedia.org/wiki/Bresenham's_line_algorithm
   bool steep = abs(toY - fromY) > abs(toX - fromX);
   if (steep) {
     int temp = fromX;
     fromX = fromY;
     fromY = temp;
     temp = toX;
     toX = toY;
     toY = temp;
   }

   int dx = abs(toX - fromX);
   int dy = abs(toY - fromY);
   int error = -dx >> 1;
   int xstep = fromX < toX ? 1 : -1;
   int ystep = fromY < toY ? 1 : -1;

   // In black pixels, looking for white, first or second time.
   int state = 0;
   // Loop up until x == toX, but not beyond
   int xLimit = toX + xstep;
   for (int x = fromX, y = fromY; x != xLimit; x += xstep) {
     int realX = steep ? y : x;
     int realY = steep ? x : y;

     // Does current pixel mean we have moved white to black or vice versa?
     if (!((state == 1) ^ image_->get(realX, realY))) {
       if (state == 2) {
         return MathUtils::distance(x, y, fromX, fromY);
       }
       state++;
     }

     error += dy;
     if (error > 0) {
       if (y == toY) {
         break;
       }
       y += ystep;
       error -= dx;
     }
   }
   // Found black-white-black; give the benefit of the doubt that the next pixel outside the image
   // is "white" so this last point at (toX+xStep,toY) is the right ending. This is really a
   // small approximation; (toX+xStep,toY+yStep) might be really correct. Ignore this.
   if (state == 2) {
     return MathUtils::distance(toX + xstep, toY, fromX, fromY);
   }
   // else we didn't find even black-white-black; no estimate is really possible
   return nan();
 }

 Ref<AlignmentPattern> Detector::findAlignmentInRegion(float overallEstModuleSize, int estAlignmentX, int estAlignmentY,
                                                       float allowanceFactor) {
   // Look for an alignment pattern (3 modules in size) around where it
   // should be
   int allowance = (int)(allowanceFactor * overallEstModuleSize);
   int alignmentAreaLeftX = max(0, estAlignmentX - allowance);
   int alignmentAreaRightX = min((int)(image_->getWidth() - 1), estAlignmentX + allowance);
   if (alignmentAreaRightX - alignmentAreaLeftX < overallEstModuleSize * 3) {
     throw zxing::ReaderException("region too small to hold alignment pattern");
   }
   int alignmentAreaTopY = max(0, estAlignmentY - allowance);
   int alignmentAreaBottomY = min((int)(image_->getHeight() - 1), estAlignmentY + allowance);
   if (alignmentAreaBottomY - alignmentAreaTopY < overallEstModuleSize * 3) {
     throw zxing::ReaderException("region too small to hold alignment pattern");
   }

   AlignmentPatternFinder alignmentFinder(image_, alignmentAreaLeftX, alignmentAreaTopY, alignmentAreaRightX
                                          - alignmentAreaLeftX, alignmentAreaBottomY - alignmentAreaTopY, overallEstModuleSize, callback_);
   return alignmentFinder.find();
 }