1.0.19: Bradley's adaptive thresholding method

ScanTailor-Advanced · Jul 26, 2023 · 9bc5e07 · 9bc5e07
1 parent b65ee43
commit 9bc5e07
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Showing 7 changed files with 99 additions and 3 deletions.
diff --git a/src/app/DefaultParamsDialog.cpp b/src/app/DefaultParamsDialog.cpp
@@ -48,6 +48,7 @@ DefaultParamsDialog::DefaultParamsDialog(QWidget* parent)
   thresholdMethodBox->addItem(tr("Otsu"), OTSU);
   thresholdMethodBox->addItem(tr("Sauvola"), SAUVOLA);
   thresholdMethodBox->addItem(tr("Wolf"), WOLF);
+  thresholdMethodBox->addItem(tr("Bradley"), BRADLEY);
   thresholdMethodBox->addItem(tr("EdgePlus"), EDGEPLUS);
   thresholdMethodBox->addItem(tr("BlurDiv"), BLURDIV);
   thresholdMethodBox->addItem(tr("EdgeDiv"), EDGEDIV);
@@ -665,8 +666,8 @@ std::unique_ptr<DefaultParams> DefaultParamsDialog::buildParams() const {
   blackWhiteOptions.setBinarizationMethod(binarizationMethod);
   blackWhiteOptions.setThresholdAdjustment(thresholdSlider->value());
   blackWhiteOptions.setSauvolaCoef(sauvolaCoef->value());
-  if (binarizationMethod == SAUVOLA || binarizationMethod == EDGEPLUS || binarizationMethod == BLURDIV
-      || binarizationMethod == EDGEDIV) {
+  if (binarizationMethod == SAUVOLA || binarizationMethod == BRADLEY || binarizationMethod == EDGEPLUS
+      || binarizationMethod == BLURDIV || binarizationMethod == EDGEDIV) {
     blackWhiteOptions.setWindowSize(sauvolaWindowSize->value());
   } else if (binarizationMethod == WOLF) {
     blackWhiteOptions.setWindowSize(wolfWindowSize->value());

diff --git a/src/core/filters/output/BlackWhiteOptions.cpp b/src/core/filters/output/BlackWhiteOptions.cpp
@@ -72,6 +72,8 @@ BinarizationMethod BlackWhiteOptions::parseBinarizationMethod(const QString& str
     return WOLF;
   } else if (str == "sauvola") {
     return SAUVOLA;
+  } else if (str == "bradley") {
+    return BRADLEY;
   } else if (str == "edgeplus") {
     return EDGEPLUS;
   } else if (str == "blurdiv") {
@@ -95,6 +97,9 @@ QString BlackWhiteOptions::formatBinarizationMethod(BinarizationMethod type) {
     case WOLF:
       str = "wolf";
       break;
+    case BRADLEY:
+      str = "bradley";
+      break;
     case EDGEPLUS:
       str = "edgeplus";
       break;

diff --git a/src/core/filters/output/BlackWhiteOptions.h b/src/core/filters/output/BlackWhiteOptions.h
@@ -9,7 +9,7 @@ class QDomDocument;
 class QDomElement;
 
 namespace output {
-enum BinarizationMethod { OTSU, SAUVOLA, WOLF, EDGEPLUS, BLURDIV, EDGEDIV };
+enum BinarizationMethod { OTSU, SAUVOLA, WOLF, BRADLEY, EDGEPLUS, BLURDIV, EDGEDIV };
 
 class BlackWhiteOptions {
  public:

diff --git a/src/core/filters/output/OptionsWidget.cpp b/src/core/filters/output/OptionsWidget.cpp
@@ -42,6 +42,7 @@ OptionsWidget::OptionsWidget(std::shared_ptr<Settings> settings, const PageSelec
   thresholdMethodBox->addItem(tr("Otsu"), OTSU);
   thresholdMethodBox->addItem(tr("Sauvola"), SAUVOLA);
   thresholdMethodBox->addItem(tr("Wolf"), WOLF);
+  thresholdMethodBox->addItem(tr("Bradley"), BRADLEY);
   thresholdMethodBox->addItem(tr("EdgePlus"), EDGEPLUS);
   thresholdMethodBox->addItem(tr("BlurDiv"), BLURDIV);
   thresholdMethodBox->addItem(tr("EdgeDiv"), EDGEDIV);
@@ -54,6 +55,8 @@ OptionsWidget::OptionsWidget(std::shared_ptr<Settings> settings, const PageSelec
   QPointer<BinarizationOptionsWidget> sauvolaBinarizationOptionsWidget
       = new SauvolaBinarizationOptionsWidget(m_settings);
   QPointer<BinarizationOptionsWidget> wolfBinarizationOptionsWidget = new WolfBinarizationOptionsWidget(m_settings);
+  QPointer<BinarizationOptionsWidget> bradleyBinarizationOptionsWidget
+      = new SauvolaBinarizationOptionsWidget(m_settings);
   QPointer<BinarizationOptionsWidget> edgeplusBinarizationOptionsWidget
       = new SauvolaBinarizationOptionsWidget(m_settings);
   QPointer<BinarizationOptionsWidget> blurdivBinarizationOptionsWidget
@@ -67,6 +70,7 @@ OptionsWidget::OptionsWidget(std::shared_ptr<Settings> settings, const PageSelec
   addBinarizationOptionsWidget(otsuBinarizationOptionsWidget);
   addBinarizationOptionsWidget(sauvolaBinarizationOptionsWidget);
   addBinarizationOptionsWidget(wolfBinarizationOptionsWidget);
+  addBinarizationOptionsWidget(bradleyBinarizationOptionsWidget);
   addBinarizationOptionsWidget(edgeplusBinarizationOptionsWidget);
   addBinarizationOptionsWidget(blurdivBinarizationOptionsWidget);
   addBinarizationOptionsWidget(edgedivBinarizationOptionsWidget);

diff --git a/src/core/filters/output/OutputGenerator.cpp b/src/core/filters/output/OutputGenerator.cpp
@@ -2306,6 +2306,14 @@ BinaryImage OutputGenerator::Processor::binarize(const QImage& image) const {
       binarized = binarizeWolf(image, windowsSize, lowerBound, upperBound, thresholdCoef, thresholdDelta);
       break;
     }
+    case BRADLEY: {
+      const double thresholdDelta = blackWhiteOptions.thresholdAdjustment();
+      const QSize windowsSize = QSize(blackWhiteOptions.getWindowSize(), blackWhiteOptions.getWindowSize());
+      const double thresholdCoef = blackWhiteOptions.getSauvolaCoef();
+
+      binarized = binarizeBradley(image, windowsSize, thresholdCoef, thresholdDelta);
+      break;
+    }
     case EDGEPLUS: {
       const double thresholdDelta = blackWhiteOptions.thresholdAdjustment();
       const QSize windowsSize = QSize(blackWhiteOptions.getWindowSize(), blackWhiteOptions.getWindowSize());

diff --git a/src/imageproc/Binarize.cpp b/src/imageproc/Binarize.cpp
@@ -201,6 +201,76 @@ BinaryImage binarizeWolf(const QImage& src,
   return bwImg;
 }  // binarizeWolf
 
+BinaryImage binarizeBradley(const QImage& src,
+                            const QSize windowSize,
+                            const double k,
+                            const double delta) {
+  if (windowSize.isEmpty()) {
+    throw std::invalid_argument("binarizeBradley: invalid windowSize");
+  }
+
+  if (src.isNull()) {
+    return BinaryImage();
+  }
+
+  QImage gray(toGrayscale(src));
+  const int w = gray.width();
+  const int h = gray.height();
+
+  IntegralImage<uint32_t> integralImage(w, h);
+
+  uint8_t* grayLine = gray.bits();
+  const int grayBpl = gray.bytesPerLine();
+
+  for (int y = 0; y < h; ++y) {
+    integralImage.beginRow();
+    for (int x = 0; x < w; ++x) {
+      const uint32_t pixel = grayLine[x];
+      integralImage.push(pixel);
+    }
+    grayLine += grayBpl;
+  }
+
+  const int windowLowerHalf = windowSize.height() >> 1;
+  const int windowUpperHalf = windowSize.height() - windowLowerHalf;
+  const int windowLeftHalf = windowSize.width() >> 1;
+  const int windowRightHalf = windowSize.width() - windowLeftHalf;
+
+  BinaryImage bwImg(w, h);
+  uint32_t* bwLine = bwImg.data();
+  const int bwWpl = bwImg.wordsPerLine();
+
+  grayLine = gray.bits();
+  for (int y = 0; y < h; ++y) {
+    const int top = std::max(0, y - windowLowerHalf);
+    const int bottom = std::min(h, y + windowUpperHalf);  // exclusive
+    for (int x = 0; x < w; ++x) {
+      const int left = std::max(0, x - windowLeftHalf);
+      const int right = std::min(w, x + windowRightHalf);  // exclusive
+      const int area = (bottom - top) * (right - left);
+      assert(area > 0);  // because windowSize > 0 and w > 0 and h > 0
+      const QRect rect(left, top, right - left, bottom - top);
+      const double windowSum = integralImage.sum(rect);
+
+      const double rArea = 1.0 / area;
+      const double mean = windowSum * rArea;
+      const double threshold = (k < 1.0) ? (mean * (1.0 - k)) : 0;
+      const uint32_t msb = uint32_t(1) << 31;
+      const uint32_t mask = msb >> (x & 31);
+      if (int(grayLine[x]) < (threshold + delta)) {
+        // black
+        bwLine[x >> 5] |= mask;
+      } else {
+        // white
+        bwLine[x >> 5] &= ~mask;
+      }
+    }
+    grayLine += grayBpl;
+    bwLine += bwWpl;
+  }
+  return bwImg;
+}  // binarizeBradley
+
 BinaryImage binarizeEdgeDiv(const QImage& src,
                             const QSize windowSize,
                             const double kep,

diff --git a/src/imageproc/Binarize.h b/src/imageproc/Binarize.h
@@ -61,6 +61,14 @@ BinaryImage binarizeWolf(const QImage& src,
                          double k = 0.3,
                          double delta = 0.0);
 
+/**
+ * \brief Image binarization using Bradley's adaptive thresholding method.
+ *
+ * Derek Bradley, Gerhard Roth. 2005. "Adaptive Thresholding Using the Integral Image".
+ * http://www.scs.carleton.ca/~roth/iit-publications-iti/docs/gerh-50002.pdf
+ */
+BinaryImage binarizeBradley(const QImage& src, QSize windowSize, double k = 0.34, double delta = 0.0);
+
 /**
  * \brief Image binarization using EdgeDiv (EdgePlus & BlurDiv) local/global thresholding method.
  *