Moved MultipleBarcodeReader and added ByQuadrantReader to try to accommodate many QR codes in an image

git-svn-id: https://zxing.googlecode.com/svn/trunk@921 59b500cc-1b3d-0410-9834-0bbf25fbcc57

core/src/com/google/zxing/multi/ByQuadrantReader.java

@@ -0,0 +1,93 @@
+/*
+ * Copyright 2009 ZXing authors
+ *
+ * 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.
+ */
+
+package com.google.zxing.multi;
+
+import com.google.zxing.Reader;
+import com.google.zxing.Result;
+import com.google.zxing.MonochromeBitmapSource;
+import com.google.zxing.ReaderException;
+import com.google.zxing.CroppedMonochromeBitmapSource;
+
+import java.util.Hashtable;
+
+/**
+ * This class attempts to decode a barcode from an image, not by scanning the whole image,
+ * but by scanning subsets of the image. This is important when there may be multiple barcodes in
+ * an image, and detecting a barcode may find parts of multiple barcode and fail to decode
+ * (e.g. QR Codes). Instead this scans the four quadrants of the image -- and also the center 'quadrant'
+ * to cover the case where a barcode is found in the center.
+ *
+ * @see MultipleBarcodeReader
+ */
+public final class ByQuadrantReader implements Reader {
+
+  private final Reader delegate;
+
+  public ByQuadrantReader(Reader delegate) {
+    this.delegate = delegate;
+  }
+
+  public Result decode(MonochromeBitmapSource image) throws ReaderException {
+    return decode(image, null);
+  }
+
+  public Result decode(MonochromeBitmapSource image, Hashtable hints) throws ReaderException {
+    
+    int width = image.getWidth();
+    int height = image.getHeight();
+    int halfWidth = width / 2;
+    int halfHeight = height / 2;
+
+    MonochromeBitmapSource topLeft = new CroppedMonochromeBitmapSource(image, 0, 0, halfWidth, halfHeight);
+    try {
+      return delegate.decode(topLeft, hints);
+    } catch (ReaderException re) {
+      // continue
+    }
+
+    MonochromeBitmapSource topRight = new CroppedMonochromeBitmapSource(image, halfWidth, 0, width, halfHeight);
+    try {
+      return delegate.decode(topRight, hints);
+    } catch (ReaderException re) {
+      // continue
+    }
+
+    MonochromeBitmapSource bottomLeft = new CroppedMonochromeBitmapSource(image, 0, halfHeight, halfWidth, height);
+    try {
+      return delegate.decode(bottomLeft, hints);
+    } catch (ReaderException re) {
+      // continue
+    }
+
+    MonochromeBitmapSource bottomRight = new CroppedMonochromeBitmapSource(image, halfWidth, halfHeight, width, height);
+    try {
+      return delegate.decode(bottomRight, hints);
+    } catch (ReaderException re) {
+      // continue
+    }
+
+    int quarterWidth = halfWidth / 2;
+    int quarterHeight = halfHeight / 2;
+    MonochromeBitmapSource center = new CroppedMonochromeBitmapSource(image,
+                                                                      quarterWidth,
+                                                                      quarterHeight,
+                                                                      width - quarterWidth,
+                                                                      height - quarterHeight);
+    return delegate.decode(center, hints);
+  }
+
+}

core/src/com/google/zxing/multi/MultipleBarcodeReader.java

@@ -14,15 +14,29 @@
  * limitations under the License.
  */
 
-package com.google.zxing;
+package com.google.zxing.multi;
+
+import com.google.zxing.Reader;
+import com.google.zxing.Result;
+import com.google.zxing.MonochromeBitmapSource;
+import com.google.zxing.ReaderException;
+import com.google.zxing.ResultPoint;
+import com.google.zxing.CroppedMonochromeBitmapSource;
 
 import java.util.Hashtable;
 import java.util.Vector;
 
 /**
- * Attempts to locate multiple barcodes in an image by repeatedly decoding portion of the image.
- * After one barcode is found, the areas left, above, right and below the barcode's {@link ResultPoint}s
- * are scanned, recursively.
+ * <p>Attempts to locate multiple barcodes in an image by repeatedly decoding portion of the image.
+ * After one barcode is found, the areas left, above, right and below the barcode's
+ * {@link com.google.zxing.ResultPoint}s are scanned, recursively.</p>
+ *
+ * <p>A caller may want to also employ {@link ByQuadrantReader} when attempting to
+ * find multiple 2D barcodes, like QR Codes, in an image, where the presence of multiple barcodes might
+ * prevent detecting any one of them.</p>
+ *
+ * <p>That is, instead of passing a {@link Reader} a caller might pass
+ * <code>new ByQuadrantReader(reader)</code>.</p>
  *
  * @author Sean Owen
  */