coders
Class ProgressiveDivisibilityEncoder

java.lang.Object
  coders.Encoder
      coders.ProgressiveDivisibilityEncoder

public class ProgressiveDivisibilityEncoder
extends Encoder

Author:

Jonathan L Dautrich Jr.

Field Summary

private int	achievedCapacity
private int	adjustmentCount
private int	escapeCount
private java.util.LinkedList<java.lang.Integer>	integerPayload
private int	n
private boolean	suppressPayloadCapacityErrors
java.util.ArrayList<java.lang.Integer>	tempCEmbedding
private int	transformableCount

Fields inherited from class coders.Encoder

encoded, encodedBitmap, originalBitmap, payload, psnr, psnrComputed

Constructor Summary

ProgressiveDivisibilityEncoder(Bitmap originalBitmap, BitSequence payload, int n)

Method Summary

void	encode() This method uses the progressive divisibility method to encode the specified payload, along with corrective information, into the bitmap.
int	getAchievedCapacity()
void	setPayloadCapacityErrorSuppression(boolean suppress)

Methods inherited from class coders.Encoder

computePSNR, getEncodedBitmap, getOriginalBitmap, getPayload

Methods inherited from class java.lang.Object

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

Field Detail

tempCEmbedding

public java.util.ArrayList<java.lang.Integer> tempCEmbedding

n

private final int n

integerPayload

private java.util.LinkedList<java.lang.Integer> integerPayload

achievedCapacity

private int achievedCapacity

transformableCount

private int transformableCount

adjustmentCount

private int adjustmentCount

escapeCount

private int escapeCount

suppressPayloadCapacityErrors

private boolean suppressPayloadCapacityErrors

Constructor Detail

ProgressiveDivisibilityEncoder

public ProgressiveDivisibilityEncoder(Bitmap originalBitmap,
                                      BitSequence payload,
                                      int n)

Method Detail

encode

public void encode()

This method uses the progressive divisibility method to encode the specified payload, along with corrective information, into the bitmap. It has two phases.

In the first phase, we consider each pixel. If the pixel can be transformed (satisfies divisibility constraint and thus information can be stored within it that causes it to no longer satisfy the divisibility constraint), it is transformed, but no data is embedded. If it cannot be transformed, it is adjusted to satisfy the divisibility constraint and its corrective data is added to the list of correction values (cValues).

In the second phase, we go through every pixel in reverse order. If it had note been transformed, it is ignored. If it had been transformed, data is embedded in it. The decoder will require each pixel to be restored to its original value before it can extract information from the subsequent pixel. Thus the corrective values must be embedded first, as they will be needed to restore up-coming pixels during decoding.

Only values between 1 and n inclusive can be embedded, but values from 0 to n inclusive may need to be encoded as corrective data. We thus implement a special escape value. Whenever we want embed a (0) or (1), we will embed a (1) followed by a (1) or (2) respectively. This allows us to keep the embedded data within range. A special escaped pair (1), (n) will be embedded to indicate the end of the corrective data and the beginning of the payload data, so that the payload data is unencumbered by the escape sequence limitations.

Specified by:

encode in class Encoder

getAchievedCapacity

public int getAchievedCapacity()

setPayloadCapacityErrorSuppression

public void setPayloadCapacityErrorSuppression(boolean suppress)