org.dvb.ui
Class DVBAlphaComposite

java.lang.Object
  extended byorg.dvb.ui.DVBAlphaComposite

public final class DVBAlphaComposite
extends java.lang.Object

This DVBAlphaComposite class implements the basic alpha compositing rules for combining source and destination pixels to achieve blending and transparency effects with graphics, images and video. The rules implemented by this class are a subset of the Porter-Duff rules described in T. Porter and T. Duff, "Compositing Digital Images", SIGGRAPH 84, 253-259.

If any input does not have an alpha channel, an alpha value of 1,0, which is completely opaque, is assumed for all pixels. A constant alpha value can also be specified to be multiplied with the alpha value of the source pixels.

The following abbreviations are used in the description of the rules:

The color and alpha components produced by the compositing operation are calculated as follows:

 	cn = (As*Ar)*Cs*Fs + Ad*Cd*Fd
 	An = (As*Ar)*Fs + Ad*Fd
  Cn = cn/An
where Fs and Fd are specified by each rule.

The alpha resulting from the compositing operation is stored in the destination if the destination has an alpha channel. Otherwise, the resulting color is divided by the resulting alpha before being stored in the destination and the alpha is discarded. If the alpha value is 0,0, the color values are set to 0,0.

Version:
10 Feb 1997
See Also:
AlphaComposite

Field Summary
static DVBAlphaComposite Clear
          DVBAlphaComposite object that implements the opaque CLEAR rule with an alpha (Ar) of 1,0f.
static int CLEAR
          Porter-Duff Clear rule.
static int DST_IN
          Porter-Duff Destination In Source rule.
static int DST_OUT
          Porter-Duff Destination Held Out By Source rule.
static int DST_OVER
          Porter-Duff Destination Over Source rule.
static DVBAlphaComposite DstIn
          DVBAlphaComposite object that implements the opaque DST_IN rule with an alpha (Ar) of 1,0f.
static DVBAlphaComposite DstOut
          DVBAlphaComposite object that implements the opaque DST_OUT rule with an alpha (Ar) of 1,0f.
static DVBAlphaComposite DstOver
          DVBAlphaComposite object that implements the opaque DST_OVER rule with an alpha (Ar) of 1,0f.
static DVBAlphaComposite Src
          DVBAlphaComposite object that implements the opaque SRC rule with an alpha (Ar) of 1,0f.
static int SRC
          Porter-Duff Source rule.
static int SRC_IN
          Porter-Duff Source In Destination rule.
static int SRC_OUT
          Porter-Duff Source Held Out By Destination rule.
static int SRC_OVER
          Porter-Duff Source Over Destination rule.
static DVBAlphaComposite SrcIn
          DVBAlphaComposite object that implements the opaque SRC_IN rule with an alpha (Ar) of 1,0f.
static DVBAlphaComposite SrcOut
          DVBAlphaComposite object that implements the opaque SRC_OUT rule with an alpha (Ar) of 1,0f.
static DVBAlphaComposite SrcOver
          DVBAlphaComposite object that implements the opaque SRC_OVER rule with an alpha (Ar) of 1,0f.
 
Method Summary
 boolean equals(java.lang.Object obj)
          Tests if the specified Object is equal to this DVBAlphaComposite object.
 float getAlpha()
          Returns the alpha value of this DVBAlphaComposite.
static DVBAlphaComposite getInstance(int rule)
          Creates an DVBAlphaComposite object with the specified rule.
static DVBAlphaComposite getInstance(int rule, float alpha)
          Creates an DVBAlphaComposite object with the specified rule and the constant alpha (Ar) to multiply with the alpha of the source (As).
 int getRule()
          Returns the compositing rule of this DVBAlphaComposite.
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

CLEAR

public static final int CLEAR
Porter-Duff Clear rule. Both the color and the alpha of the destination are cleared. Neither the source nor the destination is used as input.

Fs = 0 and Fd = 0, thus:

 	cn = 0
 	An = 0
  Cn = 0

Note that this operation is a fast drawing operation This operation is the same as using a source with alpha= 0 and the SRC rule

See Also:
Constant Field Values

SRC

public static final int SRC
Porter-Duff Source rule. The source is copied to the destination. The destination is not used as input.

Fs = 1 and Fd = 0, thus:

 	cn = (As*Ar)*Cs
 	An = As*Ar
  Cn = Cs

Note that this is a fast drawing routine

See Also:
Constant Field Values

SRC_OVER

public static final int SRC_OVER
Porter-Duff Source Over Destination rule. The source is composited over the destination.

Fs = 1 and Fd = (1-(As*Ar)), thus:

 	cn = (As*Ar)*Cs + Ad*Cd*(1-(As*Ar))
 	An = (As*Ar) + Ad*(1-(As*Ar))

Note that this can be a very slow drawing operation

See Also:
Constant Field Values

DST_OVER

public static final int DST_OVER
Porter-Duff Destination Over Source rule. The destination is composited over the source and the result replaces the destination.

Fs = (1-Ad) and Fd = 1, thus:

 	cn = (As*Ar)*Cs*(1-Ad) + Ad*Cd
 	An = (As*Ar)*(1-Ad) + Ad

Note that this can be a very slow drawing operation

See Also:
Constant Field Values

SRC_IN

public static final int SRC_IN
Porter-Duff Source In Destination rule. The part of the source lying inside of the destination replaces the destination.

Fs = Ad and Fd = 0, thus:

 	cn = (As*Ar)*Cs*Ad
 	An = (As*Ar)*Ad
  Cn = Cs

Note that this operation is faster than e.g. SRC_OVER but slower than SRC

See Also:
Constant Field Values

DST_IN

public static final int DST_IN
Porter-Duff Destination In Source rule. The part of the destination lying inside of the source replaces the destination.

Fs = 0 and Fd = (As*Ar), thus:

 	cn = Ad*Cd*(As*Ar)
 	An = Ad*(As*Ar)
  Cn = Cd

Note that this operation is faster than e.g. SRC_OVER but slower than SRC

See Also:
Constant Field Values

SRC_OUT

public static final int SRC_OUT
Porter-Duff Source Held Out By Destination rule. The part of the source lying outside of the destination replaces the destination.

Fs = (1-Ad) and Fd = 0, thus:

 	cn = (As*Ar)*Cs*(1-Ad)
 	An = (As*Ar)*(1-Ad)
  Cn = Cs

Note that this operation is faster than e.g. SRC_OVER but slower than SRC

See Also:
Constant Field Values

DST_OUT

public static final int DST_OUT
Porter-Duff Destination Held Out By Source rule. The part of the destination lying outside of the source replaces the destination.

Fs = 0 and Fd = (1-(As*Ar)), thus:

 	cn = Ad*Cd*(1-(As*Ar))
 	An = Ad*(1-(As*Ar))
  Cn = Cd

Note that this operation is faster than e.g. SRC_OVER but slower than SRC

See Also:
Constant Field Values

Clear

public static final DVBAlphaComposite Clear
DVBAlphaComposite object that implements the opaque CLEAR rule with an alpha (Ar) of 1,0f.

See Also:
CLEAR

Src

public static final DVBAlphaComposite Src
DVBAlphaComposite object that implements the opaque SRC rule with an alpha (Ar) of 1,0f.

See Also:
SRC

SrcOver

public static final DVBAlphaComposite SrcOver
DVBAlphaComposite object that implements the opaque SRC_OVER rule with an alpha (Ar) of 1,0f.

See Also:
SRC_OVER

DstOver

public static final DVBAlphaComposite DstOver
DVBAlphaComposite object that implements the opaque DST_OVER rule with an alpha (Ar) of 1,0f.

See Also:
DST_OVER

SrcIn

public static final DVBAlphaComposite SrcIn
DVBAlphaComposite object that implements the opaque SRC_IN rule with an alpha (Ar) of 1,0f.

See Also:
SRC_IN

DstIn

public static final DVBAlphaComposite DstIn
DVBAlphaComposite object that implements the opaque DST_IN rule with an alpha (Ar) of 1,0f.

See Also:
DST_IN

SrcOut

public static final DVBAlphaComposite SrcOut
DVBAlphaComposite object that implements the opaque SRC_OUT rule with an alpha (Ar) of 1,0f.

See Also:
SRC_OUT

DstOut

public static final DVBAlphaComposite DstOut
DVBAlphaComposite object that implements the opaque DST_OUT rule with an alpha (Ar) of 1,0f.

See Also:
DST_OUT
Method Detail

equals

public boolean equals(java.lang.Object obj)
Tests if the specified Object is equal to this DVBAlphaComposite object.

Parameters:
obj - the Object to test for equality
Returns:
true if obj is a DVBAlphaComposite and has the same values for rule and alpha as this object. Otherwise false shall be returned.

getAlpha

public float getAlpha()
Returns the alpha value of this DVBAlphaComposite. If this DVBAlphaComposite does not have an alpha value, 1,0 is returned.

Returns:
the alpha value of this DVBAlphaComposite.

getInstance

public static DVBAlphaComposite getInstance(int rule)
Creates an DVBAlphaComposite object with the specified rule. The value for alpha shall be 1,0f.

Parameters:
rule - the compositing rule
Returns:
an DVBAlphaComposite object with the specified rule.

getInstance

public static DVBAlphaComposite getInstance(int rule,
                                            float alpha)
Creates an DVBAlphaComposite object with the specified rule and the constant alpha (Ar) to multiply with the alpha of the source (As). The source is multiplied with the specified alpha before being composited with the destination.

Parameters:
rule - the compositing rule
alpha - the constant alpha (Ar) to be multiplied with the alpha of the source (As). alpha must be a floating point number in the inclusive range [0,0, 1,0].
Returns:
an DVBAlphaComposite object with the specified rule and the constant alpha to multiply with the alpha of the source.

getRule

public int getRule()
Returns the compositing rule of this DVBAlphaComposite.

Returns:
the compositing rule of this DVBAlphaComposite.