5 * Created by Christian Brunschen on 14/05/2008.
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6 * Copyright 2008 ZXing authors All rights reserved.
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8 * Licensed under the Apache License, Version 2.0 (the "License");
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9 * you may not use this file except in compliance with the License.
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10 * You may obtain a copy of the License at
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12 * http://www.apache.org/licenses/LICENSE-2.0
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14 * Unless required by applicable law or agreed to in writing, software
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15 * distributed under the License is distributed on an "AS IS" BASIS,
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16 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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17 * See the License for the specific language governing permissions and
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18 * limitations under the License.
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21 #include <zxing/qrcode/detector/Detector.h>
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22 #include <zxing/qrcode/detector/FinderPatternFinder.h>
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23 #include <zxing/qrcode/detector/FinderPattern.h>
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24 #include <zxing/qrcode/detector/AlignmentPattern.h>
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25 #include <zxing/qrcode/detector/AlignmentPatternFinder.h>
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26 #include <zxing/qrcode/Version.h>
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27 #include <zxing/common/GridSampler.h>
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35 using namespace std;
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37 Detector::Detector(Ref<BitMatrix> image) :
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41 Ref<BitMatrix> Detector::getImage() {
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45 Ref<DetectorResult> Detector::detect() {
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46 FinderPatternFinder finder(image_);
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47 Ref<FinderPatternInfo> info(finder.find());
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49 Ref<FinderPattern> topLeft(info->getTopLeft());
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50 Ref<FinderPattern> topRight(info->getTopRight());
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51 Ref<FinderPattern> bottomLeft(info->getBottomLeft());
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53 float moduleSize = calculateModuleSize(topLeft, topRight, bottomLeft);
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54 int dimension = computeDimension(topLeft, topRight, bottomLeft, moduleSize);
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55 Version *provisionalVersion = Version::getProvisionalVersionForDimension(dimension);
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56 int modulesBetweenFPCenters = provisionalVersion->getDimensionForVersion() - 7;
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58 Ref<AlignmentPattern> alignmentPattern;
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59 // Anything above version 1 has an alignment pattern
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60 if (provisionalVersion->getAlignmentPatternCenters().size() > 0) {
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63 // Guess where a "bottom right" finder pattern would have been
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64 float bottomRightX = topRight->getX() - topLeft->getX() + bottomLeft->getX();
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65 float bottomRightY = topRight->getY() - topLeft->getY() + bottomLeft->getY();
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68 // Estimate that alignment pattern is closer by 3 modules
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69 // from "bottom right" to known top left location
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70 float correctionToTopLeft = 1.0f - 3.0f / (float)modulesBetweenFPCenters;
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71 int estAlignmentX = (int)(topLeft->getX() + correctionToTopLeft * (bottomRightX - topLeft->getX()));
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72 int estAlignmentY = (int)(topLeft->getY() + correctionToTopLeft * (bottomRightY - topLeft->getY()));
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75 // Kind of arbitrary -- expand search radius before giving up
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76 for (int i = 4; i <= 16; i <<= 1) {
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78 alignmentPattern = findAlignmentInRegion(moduleSize, estAlignmentX, estAlignmentY, (float)i);
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80 } catch (zxing::ReaderException re) {
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84 if (alignmentPattern == 0) {
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90 Ref<PerspectiveTransform> transform = createTransform(topLeft, topRight, bottomLeft, alignmentPattern, dimension);
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91 Ref<BitMatrix> bits(sampleGrid(image_, dimension, transform));
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92 std::vector<Ref<ResultPoint> > points(alignmentPattern == 0 ? 3 : 4);
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93 points[0].reset(bottomLeft);
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94 points[1].reset(topLeft);
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95 points[2].reset(topRight);
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96 if (alignmentPattern != 0) {
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97 points[3].reset(alignmentPattern);
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100 Ref<DetectorResult> result(new DetectorResult(bits, points, transform));
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104 Ref<PerspectiveTransform> Detector::createTransform(Ref<ResultPoint> topLeft, Ref<ResultPoint> topRight, Ref <
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105 ResultPoint > bottomLeft, Ref<ResultPoint> alignmentPattern, int dimension) {
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107 float dimMinusThree = (float)dimension - 3.5f;
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108 float bottomRightX;
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109 float bottomRightY;
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110 float sourceBottomRightX;
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111 float sourceBottomRightY;
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112 if (alignmentPattern != 0) {
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113 bottomRightX = alignmentPattern->getX();
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114 bottomRightY = alignmentPattern->getY();
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115 sourceBottomRightX = sourceBottomRightY = dimMinusThree - 3.0f;
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117 // Don't have an alignment pattern, just make up the bottom-right point
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118 bottomRightX = (topRight->getX() - topLeft->getX()) + bottomLeft->getX();
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119 bottomRightY = (topRight->getY() - topLeft->getY()) + bottomLeft->getY();
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120 sourceBottomRightX = sourceBottomRightY = dimMinusThree;
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123 Ref<PerspectiveTransform> transform(PerspectiveTransform::quadrilateralToQuadrilateral(3.5f, 3.5f, dimMinusThree, 3.5f, sourceBottomRightX,
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124 sourceBottomRightY, 3.5f, dimMinusThree, topLeft->getX(), topLeft->getY(), topRight->getX(),
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125 topRight->getY(), bottomRightX, bottomRightY, bottomLeft->getX(), bottomLeft->getY()));
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130 Ref<BitMatrix> Detector::sampleGrid(Ref<BitMatrix> image, int dimension, Ref<PerspectiveTransform> transform) {
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131 GridSampler &sampler = GridSampler::getInstance();
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132 return sampler.sampleGrid(image, dimension, transform);
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135 int Detector::computeDimension(Ref<ResultPoint> topLeft, Ref<ResultPoint> topRight, Ref<ResultPoint> bottomLeft,
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136 float moduleSize) {
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137 int tltrCentersDimension = int(FinderPatternFinder::distance(topLeft, topRight) / moduleSize + 0.5f);
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138 int tlblCentersDimension = int(FinderPatternFinder::distance(topLeft, bottomLeft) / moduleSize + 0.5f);
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139 int dimension = ((tltrCentersDimension + tlblCentersDimension) >> 1) + 7;
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140 switch (dimension & 0x03) { // mod 4
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150 s << "Bad dimension: " << dimension;
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151 throw zxing::ReaderException(s.str().c_str());
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156 float Detector::calculateModuleSize(Ref<ResultPoint> topLeft, Ref<ResultPoint> topRight, Ref<ResultPoint> bottomLeft) {
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157 // Take the average
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158 return (calculateModuleSizeOneWay(topLeft, topRight) + calculateModuleSizeOneWay(topLeft, bottomLeft)) / 2.0f;
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161 float Detector::calculateModuleSizeOneWay(Ref<ResultPoint> pattern, Ref<ResultPoint> otherPattern) {
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162 float moduleSizeEst1 = sizeOfBlackWhiteBlackRunBothWays((int)pattern->getX(), (int)pattern->getY(),
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163 (int)otherPattern->getX(), (int)otherPattern->getY());
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164 float moduleSizeEst2 = sizeOfBlackWhiteBlackRunBothWays((int)otherPattern->getX(), (int)otherPattern->getY(),
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165 (int)pattern->getX(), (int)pattern->getY());
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166 if (isnan(moduleSizeEst1)) {
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167 return moduleSizeEst2;
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169 if (isnan(moduleSizeEst2)) {
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170 return moduleSizeEst1;
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172 // Average them, and divide by 7 since we've counted the width of 3 black modules,
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173 // and 1 white and 1 black module on either side. Ergo, divide sum by 14.
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174 return (moduleSizeEst1 + moduleSizeEst2) / 14.0f;
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177 float Detector::sizeOfBlackWhiteBlackRunBothWays(int fromX, int fromY, int toX, int toY) {
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179 float result = sizeOfBlackWhiteBlackRun(fromX, fromY, toX, toY);
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182 // Now count other way -- don't run off image though of course
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183 int otherToX = fromX - (toX - fromX);
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184 if (otherToX < 0) {
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185 // "to" should the be the first value not included, so, the first value off
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188 } else if (otherToX >= (int)image_->getWidth()) {
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189 otherToX = image_->getWidth();
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191 int otherToY = fromY - (toY - fromY);
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192 if (otherToY < 0) {
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194 } else if (otherToY >= (int)image_->getHeight()) {
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195 otherToY = image_->getHeight();
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197 result += sizeOfBlackWhiteBlackRun(fromX, fromY, otherToX, otherToY);
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198 return result - 1.0f; // -1 because we counted the middle pixel twice
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201 float Detector::sizeOfBlackWhiteBlackRun(int fromX, int fromY, int toX, int toY) {
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202 // Mild variant of Bresenham's algorithm;
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203 // see http://en.wikipedia.org/wiki/Bresenham's_line_algorithm
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204 bool steep = abs(toY - fromY) > abs(toX - fromX);
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214 int dx = abs(toX - fromX);
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215 int dy = abs(toY - fromY);
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216 int error = -dx >> 1;
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217 int ystep = fromY < toY ? 1 : -1;
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218 int xstep = fromX < toX ? 1 : -1;
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219 int state = 0; // In black pixels, looking for white, first or second time
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220 for (int x = fromX, y = fromY; x != toX; x += xstep) {
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222 int realX = steep ? y : x;
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223 int realY = steep ? x : y;
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224 if (state == 1) { // In white pixels, looking for black
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225 if (image_->get(realX, realY)) {
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229 if (!image_->get(realX, realY)) {
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234 if (state == 3) { // Found black, white, black, and stumbled back onto white; done
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235 int diffX = x - fromX;
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236 int diffY = y - fromY;
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237 return (float)sqrt((double)(diffX * diffX + diffY * diffY));
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245 int diffX = toX - fromX;
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246 int diffY = toY - fromY;
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247 return (float)sqrt((double)(diffX * diffX + diffY * diffY));
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250 Ref<AlignmentPattern> Detector::findAlignmentInRegion(float overallEstModuleSize, int estAlignmentX, int estAlignmentY,
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251 float allowanceFactor) {
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252 // Look for an alignment pattern (3 modules in size) around where it
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254 int allowance = (int)(allowanceFactor * overallEstModuleSize);
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255 int alignmentAreaLeftX = max(0, estAlignmentX - allowance);
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256 int alignmentAreaRightX = min((int)(image_->getWidth() - 1), estAlignmentX + allowance);
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257 int alignmentAreaTopY = max(0, estAlignmentY - allowance);
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258 int alignmentAreaBottomY = min((int)(image_->getHeight() - 1), estAlignmentY + allowance);
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260 AlignmentPatternFinder alignmentFinder(image_, alignmentAreaLeftX, alignmentAreaTopY, alignmentAreaRightX
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261 - alignmentAreaLeftX, alignmentAreaBottomY - alignmentAreaTopY, overallEstModuleSize);
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262 return alignmentFinder.find();
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