bitmaps
Class DEPixelPair

java.lang.Object
  bitmaps.PixelPair
      bitmaps.DEPixelPair

public class DEPixelPair
extends PixelPair

A black and white (single byte) pixel pair bitmaps (considers only the red component of the color pixel objects), with functionality for working with difference expansion embedding.

Author:

Jonathan L Dautrich Jr.

Field Summary

private int	avg
private int	changeable
private int	diff
private int	expandable

Fields inherited from class bitmaps.PixelPair

a, b

Constructor Summary

DEPixelPair(PixelPair pair)
Creates a new DE pixel pair from the specified PixelPair, performing a deep clone.

DEPixelPair(Pixel a, Pixel b)
Creates a new pixel pair from the two specified pixels.

Method Summary

void	contract() Contracts the current PixelPair, reducing its difference value to the floor of half its current value, and updating the pixel values accordingly.
boolean	differenceLSB() Returns true if this pixel pair's difference value's LSB is 1, false if it is zero.
boolean	embed(boolean b) Embeds the specified value in the LSB of the difference value, updating the pixel values accordingly.
void	expand(boolean b) Expands the current PixelPair, increasing its difference value and updating the pixel values accordingly.
int	getAvg() Returns the (floored) average value of the two pixels
int	getDiff() Returns the difference between the two pixels.
boolean	isChangeable() Returns true if the difference value for this pair is changeable.
boolean	isDiffWithinThreshold(int threshold) Returns true if the current pair would be selected using the given threshold.
boolean	isExpandable() Returns true if the pair is difference expandable, false otherwise
boolean	isExpansionDeterminable(int threshold) Indicates whether it can be known for certain that the current pixel either was or was not the result of an expansion.
boolean	isExpansionGuaranteed()
boolean	needsDiffLSBStorage() Deprecated.
boolean	restoreWithoutLSB() Deprecated.
private void	updatePixels() Updates the pixel values after a change to the difference or average values.
boolean	wasDefinitelyExpanded(int threshold) Indicates whether it can be known for certain that the current pixel was the result of an expansion (not an embedding) when the original criteria specified the given difference threshold.
boolean	wasDefinitelyNotExpanded(int threshold) Indicates whether it can be known for certain that the current pixel was not the result of an expansion (such that either the pair is not changeable or an embedding occurred instead) when the original criteria specified the given difference threshold.
boolean	willBeKnownDefinitelyExpanded(int threshold) Indicates whether, after expansion, the current pair will be known to have been definitely expanded, simply by considering the threshold and resulting difference value.
boolean	willBeKnownDefinitelyNotExpanded(int threshold) Indicates whether, after embedding, the current pair will be known to have been definitely not expanded, simply by considering the threshold and resulting difference value.

Methods inherited from class bitmaps.PixelPair

floorDiv, getA, getB

Methods inherited from class java.lang.Object

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

Field Detail

diff

private int diff

avg

private int avg

changeable

private int changeable

expandable

private int expandable

Constructor Detail

DEPixelPair

public DEPixelPair(Pixel a,
                   Pixel b)

Creates a new pixel pair from the two specified pixels. Warning: Changes made directly to the underlying pixel values will not be reflected in the values of the PixelPair, and will be overwritten by any functions that update the PixelPair.

Parameters:

a -

b -

DEPixelPair

public DEPixelPair(PixelPair pair)

Creates a new DE pixel pair from the specified PixelPair, performing a deep clone.

Parameters:

pair -

Method Detail

expand

public void expand(boolean b)

Expands the current PixelPair, increasing its difference value and updating the pixel values accordingly.

Parameters:

b -

contract

public void contract()

Contracts the current PixelPair, reducing its difference value to the floor of half its current value, and updating the pixel values accordingly.

embed

public boolean embed(boolean b)

Embeds the specified value in the LSB of the difference value, updating the pixel values accordingly.

Parameters:

b -

isExpandable

public boolean isExpandable()

Returns true if the pair is difference expandable, false otherwise

Returns:

isChangeable

public boolean isChangeable()

Returns true if the difference value for this pair is changeable. That is, if changing the LSB of the difference value would still produce in-range values.

Returns:

isExpansionGuaranteed

public boolean isExpansionGuaranteed()

isDiffWithinThreshold

public boolean isDiffWithinThreshold(int threshold)

Returns true if the current pair would be selected using the given threshold. That is, if diff < threshold and diff >= -threshold Computing isDiffWithinThreshold(1) is equivlent to computing isGuaranteedSelected().

Parameters:

threshold -

Returns:

wasDefinitelyExpanded

public boolean wasDefinitelyExpanded(int threshold)

Indicates whether it can be known for certain that the current pixel was the result of an expansion (not an embedding) when the original criteria specified the given difference threshold. Not cached. TODO: This can probably be made simpler.

Parameters:

threshold -

Returns:

willBeKnownDefinitelyExpanded

public boolean willBeKnownDefinitelyExpanded(int threshold)

Indicates whether, after expansion, the current pair will be known to have been definitely expanded, simply by considering the threshold and resulting difference value. Not cached. TODO: This can probably be made simpler.

Parameters:

threshold -

Returns:

willBeKnownDefinitelyNotExpanded

public boolean willBeKnownDefinitelyNotExpanded(int threshold)

Indicates whether, after embedding, the current pair will be known to have been definitely not expanded, simply by considering the threshold and resulting difference value. Simply calls wasDefinitelyNotExpanded(int), since the logic is the same for both. Like wasDefinitelyNotExpanded, returns true if the pair is not changeable. Not cached.

Parameters:

threshold -

Returns:

wasDefinitelyNotExpanded

public boolean wasDefinitelyNotExpanded(int threshold)

Indicates whether it can be known for certain that the current pixel was not the result of an expansion (such that either the pair is not changeable or an embedding occurred instead) when the original criteria specified the given difference threshold. Not cached.

Parameters:

threshold -

Returns:

isExpansionDeterminable

public boolean isExpansionDeterminable(int threshold)

Indicates whether it can be known for certain that the current pixel either was or was not the result of an expansion. If this returns false, it indicates that external information (such as from a location map) would be required to know whether this pair was expanded or not. Simply calls both wasDefinitelyExpanded(int) and wasDefinitelyNotExpanded(int). Not cached.

Parameters:

threshold -

Returns:

needsDiffLSBStorage

public boolean needsDiffLSBStorage()

Deprecated.

Indicates whether the difference value's LSB would need to be stored if this pair were encoded but not difference expanded. Simply, returns false if this pixel pair's difference value is equal to 1 or -2, true otherwise.

Returns:

restoreWithoutLSB

public boolean restoreWithoutLSB()

Deprecated.

Attempts to restore the current non-expanded pair's original difference value without needing an LSB. Only possible if -2 <= diff <= 1. Returns true if the restoration was successful. Returns false if not, in which case the original LSB must be specified. TODO: (As of 2/6/2010 not sure why this was deprecated, but perhaps this cannot be used effectively on embedding side? May have been something wrong with this...some discrepancy between changing the LSB and a simple addition. Should check it out again.)

Returns:

updatePixels

private void updatePixels()

Updates the pixel values after a change to the difference or average values.

differenceLSB

public boolean differenceLSB()

Returns true if this pixel pair's difference value's LSB is 1, false if it is zero.

Returns:

getAvg

public int getAvg()

Returns the (floored) average value of the two pixels

Returns:

getDiff

public int getDiff()

Returns the difference between the two pixels.

Returns: