com.google.zxing

Class LuminanceSource

java.lang.Object

com.google.zxing.LuminanceSource

Direct Known Subclasses:

InvertedLuminanceSource, PlanarYUVLuminanceSource, RGBLuminanceSource

public abstract class LuminanceSource
extends Object

The purpose of this class hierarchy is to abstract different bitmap implementations across platforms into a standard interface for requesting greyscale luminance values. The interface only provides immutable methods; therefore crop and rotation create copies. This is to ensure that one Reader does not modify the original luminance source and leave it in an unknown state for other Readers in the chain.

Author:

dswitkin@google.com (Daniel Switkin)

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	LuminanceSource(int width, int height)

Method Summary

Methods

Modifier and Type	Method and Description
LuminanceSource	crop(int left, int top, int width, int height) Returns a new object with cropped image data.
int	getHeight()
abstract byte[]	getMatrix() Fetches luminance data for the underlying bitmap.
abstract byte[]	getRow(int y, byte[] row) Fetches one row of luminance data from the underlying platform's bitmap.
int	getWidth()
LuminanceSource	invert()
boolean	isCropSupported()
boolean	isRotateSupported()
LuminanceSource	rotateCounterClockwise() Returns a new object with rotated image data by 90 degrees counterclockwise.
LuminanceSource	rotateCounterClockwise45() Returns a new object with rotated image data by 45 degrees counterclockwise.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

LuminanceSource

protected LuminanceSource(int width,
               int height)

Method Detail

getRow

public abstract byte[] getRow(int y,
            byte[] row)

Fetches one row of luminance data from the underlying platform's bitmap. Values range from 0 (black) to 255 (white). Because Java does not have an unsigned byte type, callers will have to bitwise and with 0xff for each value. It is preferable for implementations of this method to only fetch this row rather than the whole image, since no 2D Readers may be installed and getMatrix() may never be called.

Parameters:

y - The row to fetch, which must be in [0,getHeight())

row - An optional preallocated array. If null or too small, it will be ignored. Always use the returned object, and ignore the .length of the array.

Returns:

An array containing the luminance data.

getMatrix

public abstract byte[] getMatrix()

Fetches luminance data for the underlying bitmap. Values should be fetched using: int luminance = array[y * width + x] & 0xff

Returns:

A row-major 2D array of luminance values. Do not use result.length as it may be larger than width * height bytes on some platforms. Do not modify the contents of the result.

getWidth

public final int getWidth()

Returns:

The width of the bitmap.

getHeight

public final int getHeight()

Returns:

The height of the bitmap.

isCropSupported

public boolean isCropSupported()

Returns:

Whether this subclass supports cropping.

crop

public LuminanceSource crop(int left,
                   int top,
                   int width,
                   int height)

Returns a new object with cropped image data. Implementations may keep a reference to the original data rather than a copy. Only callable if isCropSupported() is true.

Parameters:

left - The left coordinate, which must be in [0,getWidth())

top - The top coordinate, which must be in [0,getHeight())

width - The width of the rectangle to crop.

height - The height of the rectangle to crop.

Returns:

A cropped version of this object.

isRotateSupported

public boolean isRotateSupported()

Returns:

Whether this subclass supports counter-clockwise rotation.

invert

public LuminanceSource invert()

Returns:

a wrapper of this LuminanceSource which inverts the luminances it returns -- black becomes white and vice versa, and each value becomes (255-value).

rotateCounterClockwise

public LuminanceSource rotateCounterClockwise()

Returns a new object with rotated image data by 90 degrees counterclockwise. Only callable if isRotateSupported() is true.

Returns:

A rotated version of this object.

rotateCounterClockwise45

public LuminanceSource rotateCounterClockwise45()

Returns a new object with rotated image data by 45 degrees counterclockwise. Only callable if isRotateSupported() is true.

Returns:

A rotated version of this object.

toString

public final String toString()

Overrides:

toString in class Object