Issue 1604 Add LuminanceSource.invert() method

git-svn-id: https://zxing.googlecode.com/svn/trunk@2574 59b500cc-1b3d-0410-9834-0bbf25fbcc57

core/src/com/google/zxing/InvertedLuminanceSource.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2013 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;
+
+/**
+ * A wrapper implementation of {@link LuminanceSource} which inverts the luminances it returns -- black becomes
+ * white and vice versa, and each value becomes (255-value).
+ * 
+ * @author Sean Owen
+ */
+public final class InvertedLuminanceSource extends LuminanceSource {
+
+  private final LuminanceSource delegate;
+
+  public InvertedLuminanceSource(LuminanceSource delegate) {
+    super(delegate.getWidth(), delegate.getHeight());
+    this.delegate = delegate;
+  }
+
+  @Override
+  public byte[] getRow(int y, byte[] row) {
+    row = delegate.getRow(y, row);
+    int width = getWidth();
+    for (int i = 0; i < width; i++) {
+      row[i] = (byte) (255 - (row[i] & 0xFF));
+    }
+    return row;
+  }
+
+  @Override
+  public byte[] getMatrix() {
+    byte[] matrix = delegate.getMatrix();
+    int length = getWidth() * getHeight();
+    byte[] invertedMatrix = new byte[length];
+    for (int i = 0; i < length; i++) {
+      invertedMatrix[i] = (byte) (255 - (matrix[i] & 0xFF));
+    }
+    return invertedMatrix;
+  }
+  
+}

core/src/com/google/zxing/LuminanceSource.java

@@ -101,6 +101,14 @@ public abstract class LuminanceSource {
     return false;
   }
 
+  /**
+   * @return a wrapper of this {@code LuminanceSource} which inverts the luminances it returns -- black becomes
+   *  white and vice versa, and each value becomes (255-value).
+   */
+  public final LuminanceSource invert() {
+    return new InvertedLuminanceSource(this);
+  }
+
   /**
    * Returns a new object with rotated image data by 90 degrees counterclockwise.
    * Only callable if {@link #isRotateSupported()} is true.