C++: binarizer updates

[zxing.git] / cpp / core / src / zxing / common / HybridBinarizer.cpp

diff --git a/cpp/core/src/zxing/common/HybridBinarizer.cpp b/cpp/core/src/zxing/common/HybridBinarizer.cpp
new file mode 100644 (file)
index 0000000..65d03ee
--- /dev/null
+++ b/cpp/core/src/zxing/common/HybridBinarizer.cpp
@@ -0,0 +1,140 @@
+/*
+ *  HybridBinarizer.cpp
+ *  zxing
+ *
+ *  Copyright 2010 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/common/HybridBinarizer.h>
+
+#include <zxing/common/IllegalArgumentException.h>
+
+namespace zxing {
+using namespace std;
+
+static const int MINIMUM_DIMENSION = 40;
+
+static const int LUMINANCE_BITS = 5;
+static const int LUMINANCE_SHIFT = 8 - LUMINANCE_BITS;
+static const int LUMINANCE_BUCKETS = 1 << LUMINANCE_BITS;
+
+HybridBinarizer::HybridBinarizer(Ref<LuminanceSource> source) :
+  GlobalHistogramBinarizer(source), cached_matrix_(NULL), cached_row_(NULL), cached_row_num_(-1) {
+
+}
+
+HybridBinarizer::~HybridBinarizer() {
+}
+
+
+Ref<BitMatrix> HybridBinarizer::getBlackMatrix() {
+  binarizeEntireImage();
+  return cached_matrix_;
+}
+
+Ref<Binarizer> HybridBinarizer::createBinarizer(Ref<LuminanceSource> source) {
+  return Ref<Binarizer> (new HybridBinarizer(source));
+}
+
+void HybridBinarizer::binarizeEntireImage() {
+  if (cached_matrix_ == NULL) {
+    Ref<LuminanceSource> source = getLuminanceSource();
+    if (source->getWidth() >= MINIMUM_DIMENSION && source->getHeight() >= MINIMUM_DIMENSION) {
+      unsigned char* luminances = source->getMatrix();
+      int width = source->getWidth();
+      int height = source->getHeight();
+      int subWidth = width >> 3;
+      int subHeight = height >> 3;
+      int *blackPoints = calculateBlackPoints(luminances, subWidth, subHeight, width);
+      cached_matrix_.reset(new BitMatrix(width,height));
+      calculateThresholdForBlock(luminances, subWidth, subHeight, width, blackPoints, cached_matrix_);
+      delete [] blackPoints;
+    } else {
+      // If the image is too small, fall back to the global histogram approach.
+      cached_matrix_.reset(GlobalHistogramBinarizer::getBlackMatrix());
+    }
+  }
+}
+
+void HybridBinarizer::calculateThresholdForBlock(unsigned char* luminances, int subWidth, int subHeight,
+    int stride, int blackPoints[], Ref<BitMatrix> matrix) {
+  for (int y = 0; y < subHeight; y++) {
+    for (int x = 0; x < subWidth; x++) {
+      int left = (x > 1) ? x : 2;
+      left = (left < subWidth - 2) ? left : subWidth - 3;
+      int top = (y > 1) ? y : 2;
+      top = (top < subHeight - 2) ? top : subHeight - 3;
+      int sum = 0;
+      for (int z = -2; z <= 2; z++) {
+        int *blackRow = &blackPoints[(top + z) * subWidth];
+        sum += blackRow[left - 2];
+        sum += blackRow[left - 1];
+        sum += blackRow[left];
+        sum += blackRow[left + 1];
+        sum += blackRow[left + 2];
+      }
+      int average = sum / 25;
+      threshold8x8Block(luminances, x << 3, y << 3, average, stride, matrix);
+    }
+  }
+}
+
+void HybridBinarizer::threshold8x8Block(unsigned char* luminances, int xoffset, int yoffset, int threshold,
+    int stride, Ref<BitMatrix> matrix) {
+  for (int y = 0; y < 8; y++) {
+    int offset = (yoffset + y) * stride + xoffset;
+    for (int x = 0; x < 8; x++) {
+      int pixel = luminances[offset + x] & 0xff;
+      if (pixel < threshold) {
+        matrix->set(xoffset + x, yoffset + y);
+      }
+    }
+  }
+}
+
+int* HybridBinarizer::calculateBlackPoints(unsigned char* luminances, int subWidth, int subHeight,
+    int stride) {
+  int *blackPoints = new int[subHeight * subWidth];
+  for (int y = 0; y < subHeight; y++) {
+    for (int x = 0; x < subWidth; x++) {
+      int sum = 0;
+      int min = 255;
+      int max = 0;
+      for (int yy = 0; yy < 8; yy++) {
+        int offset = ((y << 3) + yy) * stride + (x << 3);
+        for (int xx = 0; xx < 8; xx++) {
+          int pixel = luminances[offset + xx] & 0xff;
+          sum += pixel;
+          if (pixel < min) {
+            min = pixel;
+          }
+          if (pixel > max) {
+            max = pixel;
+          }
+        }
+      }
+
+      // If the contrast is inadequate, use half the minimum, so that this block will be
+      // treated as part of the white background, but won't drag down neighboring blocks
+      // too much.
+      int average = (max - min > 24) ? (sum >> 6) : (min >> 1);
+      blackPoints[y * subWidth + x] = average;
+    }
+  }
+  return blackPoints;
+}
+
+} // namespace zxing
+