com.google.zxing.common

Class HybridBinarizer

java.lang.Object

com.google.zxing.Binarizer

com.google.zxing.common.GlobalHistogramBinarizer

com.google.zxing.common.HybridBinarizer

public final class HybridBinarizer
extends GlobalHistogramBinarizer

This class implements a local thresholding algorithm, which while slower than the GlobalHistogramBinarizer, is fairly efficient for what it does. It is designed for high frequency images of barcodes with black data on white backgrounds. For this application, it does a much better job than a global blackpoint with severe shadows and gradients. However it tends to produce artifacts on lower frequency images and is therefore not a good general purpose binarizer for uses outside ZXing. This class extends GlobalHistogramBinarizer, using the older histogram approach for 1D readers, and the newer local approach for 2D readers. 1D decoding using a per-row histogram is already inherently local, and only fails for horizontal gradients. We can revisit that problem later, but for now it was not a win to use local blocks for 1D. This Binarizer is the default for the unit tests and the recommended class for library users.

Author:

dswitkin@google.com (Daniel Switkin)

Constructor Summary

Constructors

Constructor and Description
HybridBinarizer(LuminanceSource source)

Method Summary

Modifier and Type	Method and Description
Binarizer	createBinarizer(LuminanceSource source) Creates a new object with the same type as this Binarizer implementation, but with pristine state.
BitMatrix	getBlackMatrix() Calculates the final BitMatrix once for all requests.

Methods inherited from class com.google.zxing.common.GlobalHistogramBinarizer

getBlackRow

Methods inherited from class com.google.zxing.Binarizer

getHeight, getLuminanceSource, getWidth

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

HybridBinarizer

public HybridBinarizer(LuminanceSource source)

Method Detail

getBlackMatrix

public BitMatrix getBlackMatrix()
                         throws NotFoundException

Calculates the final BitMatrix once for all requests. This could be called once from the constructor instead, but there are some advantages to doing it lazily, such as making profiling easier, and not doing heavy lifting when callers don't expect it.

Overrides:

getBlackMatrix in class GlobalHistogramBinarizer

Returns:

The 2D array of bits for the image (true means black).

Throws:

NotFoundException - if image can't be binarized to make a matrix

createBinarizer

public Binarizer createBinarizer(LuminanceSource source)

Description copied from class: Binarizer

Creates a new object with the same type as this Binarizer implementation, but with pristine state. This is needed because Binarizer implementations may be stateful, e.g. keeping a cache of 1 bit data. See Effective Java for why we can't use Java's clone() method.

Overrides:

createBinarizer in class GlobalHistogramBinarizer

Parameters:

source - The LuminanceSource this Binarizer will operate on.

Returns:

A new concrete Binarizer implementation object.