DVBAlphaComposite (ocap 1.3.1 API)

java.lang.Object
- org.dvb.ui.DVBAlphaComposite

```
public final class DVBAlphaComposite
extends 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:
- Cs = one of the color components of the source pixel without alpha.
- cs = color component of a source pixel premultimlied with alpha (cs = As*Ar*Cs)
- Cd = one of the color components of the destination pixel without alpha.
- cd = color component of a destination pixel premultimlied with alpha
- Cn = the new constructed color without alpha.
- cn = the new constructed color pre-multiplied with alpha
- As = alpha component of the source pixel.
- Ad = alpha component of the destination pixel.
- An = the new alpha after compositing
- Ar = alpha, specified by getInstance(int Rule, float Ar). Unless otherwise specified Ar = 1,0f
- Fs = fraction of the source pixel that contributes to the output.
- Fd = fraction of the input destination pixel that contributes to the output.
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

Fields
Modifier and Type	Field and Description
`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

Methods
Modifier and Type	Method and Description
`boolean`	`equals(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(Object obj)
```
    Tests if the specified Object is equal to this DVBAlphaComposite object.
    
    Overrides:
    
    equals in class 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.
    See Also:
    Object.hashCode(), Hashtable
  - 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.

Class DVBAlphaComposite

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

CLEAR

SRC

SRC_OVER

DST_OVER

SRC_IN

DST_IN

SRC_OUT

DST_OUT

Clear

Src

SrcOver

DstOver

SrcIn

DstIn

SrcOut

DstOut

Method Detail

equals

getAlpha

getInstance

getInstance

getRule