turn pngBytes;
}

/**
* Creates an array of bytes that is the PNG equivalent of the current image.
* Alpha encoding is determined by its setting in the constructor.
*
* @return an array of bytes, or null if there was a problem
*/
public byte[] pngEncode()
{
return pngEncode( encodeAlpha );
}

/**
* Set the alpha encoding on or off.
*
* @param encodeAlpha false=no, true=yes
*/
public void setEncodeAlpha( boolean encodeAlpha )
{
this.encodeAlpha = encodeAlpha;
}

/**
* Retrieve alpha encoding status.
*
* @return boolean false=no, true=yes
*/
public boolean getEncodeAlpha()
{
return encodeAlpha;
}

/**
* Set the filter to use
*
* @param whichFilter from constant list
*/
public void setFilter( int whichFilter )
{
this.filter = FILTER_NONE;
if ( whichFilter <= FILTER_LAST )
{
this.filter = whichFilter;
}
}

/**
* Retrieve filtering scheme
*
* @return int (see constant list)
*/
public int getFilter()
{
return filter;
}

/**
* Set the compression level to use
*
* @param level 0 through 9
*/
public void setCompressionLevel( int level )
{
if ( level >= 0 && level <= 9)
{
this.compressionLevel = level;
}
}

/**
* Retrieve compression level
*
* @return int in range 0-9
*/
public int getCompressionLevel()
{
return compressionLevel;
}

/**
* Increase or decrease the length of a byte array.
*
* @param array The original array.
* @param newLength The length you wish the new array to have.
* @return Array of newly desired length. If shorter than the
* original, the trailing elements are truncated.
*/
protected byte[] resizeByteArray( byte[] array, int newLength )
{
byte[] newArray = new byte[newLength];
int oldLength = array.length;

System.arraycopy( array, 0, newArray, 0,
Math.min( oldLength, newLength ) );
return newArray;
}

/**
* Write an array of bytes into the pngBytes array.
* Note: This routine has the side effect of updating
* maxPos, the largest element written in the array.
* The array is resized by 1000 bytes or the length
* of the data to be written, whichever is larger.
*
* @param data The data to be written into pngBytes.
* @param offset The starting point to write to.
* @return The next place to be written to in the pngBytes array.
*/
protected int writeBytes( byte[] data, int offset )
{
maxPos = Math.max( maxPos, offset + data.length );
if (data.length + offset > pngBytes.length)
{
pngBytes = resizeByteArray( pngBytes, pngBytes.length +
Math.max( 1000, data.length ) );
}
System.arraycopy( data, 0, pngBytes, offset, data.length );
return offset + data.length;
}

/**
* Write an array of bytes into the pngBytes array, specifying number of bytes to write.
* Note: This routine has the side effect of updating
* maxPos, the largest element written in the array.
* The array is resized by 1000 bytes or the length
* of the data to be written, whichever is larger.
*
* @param data The data to be written into pngBytes.
* @param nBytes The number of bytes to be written.
* @param offset The starting point to write to.
* @return The next place to be written to in the pngBytes array.
*/
protected int writeBytes( byte[] data, int nBytes, int offset )
{
maxPos = Math.max( maxPos, offset + nBytes );
if (nBytes + offset > pngBytes.length)
{
pngBytes = resizeByteArray( pngBytes, pngBytes.length +
Math.max( 1000, nBytes ) );
}
System.arraycopy( data, 0, pngBytes, offset, nBytes );
return offset + nBytes;
}

/**
* Write a two-byte integer into the pngBytes array at a given position.
*
* @param n The integer to be written into pngBytes.
* @param offset The starting point to write to.
* @return The next place to be written to in the pngBytes array.
*/
protected int writeInt2( int n, int offset )
{
byte[] temp = { (byte)((n >> 8) & 0xff),
(byte) (n & 0xff) };
return writeBytes( temp, offset );
}

/**
* Write a four-byte integer into the pngBytes array at a given position.
*
* @param n The integer to be written into pngBytes.
* @param offset The starting point to write to.
* @return The next place to be written to in the pngBytes array.
*/
protected int writeInt4( int n, int offset )
{
byte[] temp = { (byte)((n >> 24) & 0xff),
(byte) ((n >> 16) & 0xff ),
(byte) ((n >> 8) & 0xff ),
(byte) ( n & 0xff ) };
return writeBytes( temp, offset );
}

/**
* Write a single byte into the pngBytes array at a given position.
*
* @param n The integer to be written into pngBytes.
* @param offset The starting point to write to.
* @return The next place to be written to in the pngBytes array.
*/
protected int writeByte( int b, int offset )
{
byte[] temp = { (byte) b };
return writeBytes( temp, offset );
}

/**
* Write a string into the pngBytes array at a given position.
* This uses the getBytes method, so the encoding used will
* be its default.
*
* @param n The integer to be written into pngBytes.
* @param offset The starting point to write to.
* @return The next place to be written to in the pngBytes array.
* @see java.lang.String#getBytes()
*/
protected int writeString( String s, int offset )
{
return writeBytes( s.getBytes(), offset );
}

/**
* Writ