2 * Copyright 2009 ZXing authors
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
17 package com.google.zxing;
19 import com.google.zxing.common.BitArray;
20 import com.google.zxing.common.BitMatrix;
23 * This class hierarchy provides a set of methods to convert luminance data to 1 bit data.
24 * It allows the algorithm to vary polymorphically, for example allowing a very expensive
25 * thresholding technique for servers and a fast one for mobile. It also permits the implementation
26 * to vary, e.g. a JNI version for Android and a Java fallback version for other platforms.
28 * @author dswitkin@google.com (Daniel Switkin)
30 public abstract class Binarizer {
32 private final LuminanceSource source;
34 protected Binarizer(LuminanceSource source) {
36 throw new IllegalArgumentException("Source must be non-null.");
41 public LuminanceSource getLuminanceSource() {
46 * Converts one row of luminance data to 1 bit data. May actually do the conversion, or return
47 * cached data. Callers should assume this method is expensive and call it as seldom as possible.
48 * This method is intended for decoding 1D barcodes and may choose to apply sharpening.
49 * For callers which only examine one row of pixels at a time, the same BitArray should be reused
50 * and passed in with each call for performance. However it is legal to keep more than one row
51 * at a time if needed.
53 * @param y The row to fetch, 0 <= y < bitmap height.
54 * @param row An optional preallocated array. If null or too small, it will be ignored.
55 * If used, the Binarizer will call BitArray.clear(). Always use the returned object.
56 * @return The array of bits for this row (true means black).
58 public abstract BitArray getBlackRow(int y, BitArray row) throws NotFoundException;
61 * Converts a 2D array of luminance data to 1 bit data. As above, assume this method is expensive
62 * and do not call it repeatedly. This method is intended for decoding 2D barcodes and may or
63 * may not apply sharpening. Therefore, a row from this matrix may not be identical to one
64 * fetched using getBlackRow(), so don't mix and match between them.
66 * @return The 2D array of bits for the image (true means black).
68 public abstract BitMatrix getBlackMatrix() throws NotFoundException;
71 * Creates a new object with the same type as this Binarizer implementation, but with pristine
72 * state. This is needed because Binarizer implementations may be stateful, e.g. keeping a cache
73 * of 1 bit data. See Effective Java for why we can't use Java's clone() method.
75 * @param source The LuminanceSource this Binarizer will operate on.
76 * @return A new concrete Binarizer implementation object.
78 public abstract Binarizer createBinarizer(LuminanceSource source);