Package com.google.zxing.common
Class GlobalHistogramBinarizer
- java.lang.Object
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- com.google.zxing.Binarizer
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- com.google.zxing.common.GlobalHistogramBinarizer
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- Direct Known Subclasses:
HybridBinarizer
public class GlobalHistogramBinarizer extends Binarizer
This Binarizer implementation uses the old ZXing global histogram approach. It is suitable for low-end mobile devices which don't have enough CPU or memory to use a local thresholding algorithm. However, because it picks a global black point, it cannot handle difficult shadows and gradients. Faster mobile devices and all desktop applications should probably use HybridBinarizer instead.
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Field Summary
Fields Modifier and Type Field Description private int[]
buckets
private static byte[]
EMPTY
private static int
LUMINANCE_BITS
private static int
LUMINANCE_BUCKETS
private static int
LUMINANCE_SHIFT
private byte[]
luminances
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Constructor Summary
Constructors Constructor Description GlobalHistogramBinarizer(LuminanceSource source)
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description Binarizer
createBinarizer(LuminanceSource source)
Creates a new object with the same type as this Binarizer implementation, but with pristine state.private static int
estimateBlackPoint(int[] buckets)
BitMatrix
getBlackMatrix()
Converts a 2D array of luminance data to 1 bit data.BitArray
getBlackRow(int y, BitArray row)
Converts one row of luminance data to 1 bit data.private void
initArrays(int luminanceSize)
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Methods inherited from class com.google.zxing.Binarizer
getHeight, getLuminanceSource, getWidth
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Field Detail
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LUMINANCE_BITS
private static final int LUMINANCE_BITS
- See Also:
- Constant Field Values
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LUMINANCE_SHIFT
private static final int LUMINANCE_SHIFT
- See Also:
- Constant Field Values
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LUMINANCE_BUCKETS
private static final int LUMINANCE_BUCKETS
- See Also:
- Constant Field Values
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EMPTY
private static final byte[] EMPTY
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luminances
private byte[] luminances
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buckets
private final int[] buckets
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Constructor Detail
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GlobalHistogramBinarizer
public GlobalHistogramBinarizer(LuminanceSource source)
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Method Detail
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getBlackRow
public BitArray getBlackRow(int y, BitArray row) throws NotFoundException
Description copied from class:Binarizer
Converts one row of luminance data to 1 bit data. May actually do the conversion, or return cached data. Callers should assume this method is expensive and call it as seldom as possible. This method is intended for decoding 1D barcodes and may choose to apply sharpening. For callers which only examine one row of pixels at a time, the same BitArray should be reused and passed in with each call for performance. However it is legal to keep more than one row at a time if needed.- Specified by:
getBlackRow
in classBinarizer
- Parameters:
y
- The row to fetch, which must be in [0, bitmap height)row
- An optional preallocated array. If null or too small, it will be ignored. If used, the Binarizer will call BitArray.clear(). Always use the returned object.- Returns:
- The array of bits for this row (true means black).
- Throws:
NotFoundException
- if row can't be binarized
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getBlackMatrix
public BitMatrix getBlackMatrix() throws NotFoundException
Description copied from class:Binarizer
Converts a 2D array of luminance data to 1 bit data. As above, assume this method is expensive and do not call it repeatedly. This method is intended for decoding 2D barcodes and may or may not apply sharpening. Therefore, a row from this matrix may not be identical to one fetched using getBlackRow(), so don't mix and match between them.- Specified by:
getBlackMatrix
in classBinarizer
- Returns:
- The 2D array of bits for the image (true means black).
- Throws:
NotFoundException
- if image can't be binarized to make a matrix
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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.- Specified by:
createBinarizer
in classBinarizer
- Parameters:
source
- The LuminanceSource this Binarizer will operate on.- Returns:
- A new concrete Binarizer implementation object.
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initArrays
private void initArrays(int luminanceSize)
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estimateBlackPoint
private static int estimateBlackPoint(int[] buckets) throws NotFoundException
- Throws:
NotFoundException
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