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JavaTM 2 Platform Std. Ed. v1.4.2 |
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java.lang.Objectjava.awt.AlphaComposite
This AlphaComposite class implements the basic alpha
compositing rules for combining source and destination pixels to achieve
blending and transparency effects with graphics and images.
The rules implemented by this class are the set of 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:
Cd = Cs*Fs + Cd*Fd Ad = As*Fs + Ad*Fdwhere Fs and Fd are specified by each rule. The above equations assume that both source and destination pixels have the color components premultiplied by the alpha component. Similarly, the equations expressed in the definitions of compositing rules below assume premultiplied alpha.
For performance reasons, it is preferrable that Rasters passed to the compose
method of a CompositeContext object created by the
AlphaComposite class have premultiplied data.
If either source or destination Rasters are not premultiplied, however,
appropriate conversions are performed before and after the compositing
operation.
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.
Composite,
CompositeContext| Field Summary | |
static AlphaComposite |
Clear
AlphaComposite object that implements the opaque CLEAR rule
with an alpha of 1.0f. |
static int |
CLEAR
Porter-Duff Clear rule. |
static AlphaComposite |
Dst
AlphaComposite object that implements the opaque DST rule
with an alpha of 1.0f. |
static int |
DST
Porter-Duff Destination rule. |
static int |
DST_ATOP
Porter-Duff Destination Atop Source 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 AlphaComposite |
DstAtop
AlphaComposite object that implements the opaque DST_ATOP rule
with an alpha of 1.0f. |
static AlphaComposite |
DstIn
AlphaComposite object that implements the opaque DST_IN rule
with an alpha of 1.0f. |
static AlphaComposite |
DstOut
AlphaComposite object that implements the opaque DST_OUT rule
with an alpha of 1.0f. |
static AlphaComposite |
DstOver
AlphaComposite object that implements the opaque DST_OVER rule
with an alpha of 1.0f. |
static AlphaComposite |
Src
AlphaComposite object that implements the opaque SRC rule
with an alpha of 1.0f. |
static int |
SRC
Porter-Duff Source rule. |
static int |
SRC_ATOP
Porter-Duff Source Atop Destination 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 AlphaComposite |
SrcAtop
AlphaComposite object that implements the opaque SRC_ATOP rule
with an alpha of 1.0f. |
static AlphaComposite |
SrcIn
AlphaComposite object that implements the opaque SRC_IN rule
with an alpha of 1.0f. |
static AlphaComposite |
SrcOut
AlphaComposite object that implements the opaque SRC_OUT rule
with an alpha of 1.0f. |
static AlphaComposite |
SrcOver
AlphaComposite object that implements the opaque SRC_OVER rule
with an alpha of 1.0f. |
static AlphaComposite |
Xor
AlphaComposite object that implements the opaque XOR rule
with an alpha of 1.0f. |
static int |
XOR
Porter-Duff Source Xor Destination rule. |
| Method Summary | |
CompositeContext |
createContext(ColorModel srcColorModel,
ColorModel dstColorModel,
RenderingHints hints)
Creates a context for the compositing operation. |
boolean |
equals(Object obj)
Determines whether the specified object is equal to this AlphaComposite. |
float |
getAlpha()
Returns the alpha value of this AlphaComposite. |
static AlphaComposite |
getInstance(int rule)
Creates an AlphaComposite object with the specified rule. |
static AlphaComposite |
getInstance(int rule,
float alpha)
Creates an AlphaComposite object with the specified rule and
the constant alpha to multiply with the alpha of the source. |
int |
getRule()
Returns the compositing rule of this AlphaComposite. |
int |
hashCode()
Returns the hashcode for this composite. |
| Methods inherited from class java.lang.Object |
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait |
| Field Detail |
public static final int CLEAR
Fs = 0 and Fd = 0, thus:
Cd = 0 Ad = 0
public static final int SRC
Fs = 1 and Fd = 0, thus:
Cd = Cs Ad = As
public static final int DST
Fs = 0 and Fd = 1, thus:
Cd = Cd Ad = Ad
public static final int SRC_OVER
Fs = 1 and Fd = (1-As), thus:
Cd = Cs + Cd*(1-As) Ad = As + Ad*(1-As)
public static final int DST_OVER
Fs = (1-Ad) and Fd = 1, thus:
Cd = Cs*(1-Ad) + Cd Ad = As*(1-Ad) + Ad
public static final int SRC_IN
Fs = Ad and Fd = 0, thus:
Cd = Cs*Ad Ad = As*Ad
public static final int DST_IN
Fs = 0 and Fd = As, thus:
Cd = Cd*As Ad = Ad*As
public static final int SRC_OUT
Fs = (1-Ad) and Fd = 0, thus:
Cd = Cs*(1-Ad) Ad = As*(1-Ad)
public static final int DST_OUT
Fs = 0 and Fd = (1-As), thus:
Cd = Cd*(1-As) Ad = Ad*(1-As)
public static final int SRC_ATOP
Fs = Ad and Fd = (1-As), thus:
Cd = Cs*Ad + Cd*(1-As) Ad = As*Ad + Ad*(1-As) = Ad
public static final int DST_ATOP
Fs = (1-Ad) and Fd = As, thus:
Cd = Cs*(1-Ad) + Cd*As Ad = As*(1-Ad) + Ad*As = As
public static final int XOR
Fs = (1-Ad) and Fd = (1-As), thus:
Cd = Cs*(1-Ad) + Cd*(1-As) Ad = As*(1-Ad) + Ad*(1-As)
public static final AlphaComposite Clear
AlphaComposite object that implements the opaque CLEAR rule
with an alpha of 1.0f.
CLEARpublic static final AlphaComposite Src
AlphaComposite object that implements the opaque SRC rule
with an alpha of 1.0f.
SRCpublic static final AlphaComposite Dst
AlphaComposite object that implements the opaque DST rule
with an alpha of 1.0f.
DSTpublic static final AlphaComposite SrcOver
AlphaComposite object that implements the opaque SRC_OVER rule
with an alpha of 1.0f.
SRC_OVERpublic static final AlphaComposite DstOver
AlphaComposite object that implements the opaque DST_OVER rule
with an alpha of 1.0f.
DST_OVERpublic static final AlphaComposite SrcIn
AlphaComposite object that implements the opaque SRC_IN rule
with an alpha of 1.0f.
SRC_INpublic static final AlphaComposite DstIn
AlphaComposite object that implements the opaque DST_IN rule
with an alpha of 1.0f.
DST_INpublic static final AlphaComposite SrcOut
AlphaComposite object that implements the opaque SRC_OUT rule
with an alpha of 1.0f.
SRC_OUTpublic static final AlphaComposite DstOut
AlphaComposite object that implements the opaque DST_OUT rule
with an alpha of 1.0f.
DST_OUTpublic static final AlphaComposite SrcAtop
AlphaComposite object that implements the opaque SRC_ATOP rule
with an alpha of 1.0f.
SRC_ATOPpublic static final AlphaComposite DstAtop
AlphaComposite object that implements the opaque DST_ATOP rule
with an alpha of 1.0f.
DST_ATOPpublic static final AlphaComposite Xor
AlphaComposite object that implements the opaque XOR rule
with an alpha of 1.0f.
XOR| Method Detail |
public static AlphaComposite getInstance(int rule)
AlphaComposite object with the specified rule.
rule - the compositing rule
IllegalArgumentException - if rule is not one of
the following: CLEAR, SRC, DST,
SRC_OVER, DST_OVER, SRC_IN,
DST_IN, SRC_OUT, DST_OUT,
SRC_ATOP, DST_ATOP, or XOR
public static AlphaComposite getInstance(int rule,
float alpha)
AlphaComposite object with the specified rule and
the constant alpha to multiply with the alpha of the source.
The source is multiplied with the specified alpha before being composited
with the destination.
rule - the compositing rulealpha - the constant alpha to be multiplied with the alpha of
the source. alpha must be a floating point number in the
inclusive range [0.0, 1.0].
IllegalArgumentException - if
alpha is less than 0.0 or greater than 1.0, or if
rule is not one of
the following: CLEAR, SRC, DST,
SRC_OVER, DST_OVER, SRC_IN,
DST_IN, SRC_OUT, DST_OUT,
SRC_ATOP, DST_ATOP, or XOR
public CompositeContext createContext(ColorModel srcColorModel,
ColorModel dstColorModel,
RenderingHints hints)
createContext in interface CompositesrcColorModel - the ColorModel of the sourcedstColorModel - the ColorModel of the destinationhints - the hint that the context object uses to choose between
rendering alternatives
CompositeContext object to be used to perform
compositing operations.public float getAlpha()
AlphaComposite. If this
AlphaComposite does not have an alpha value, 1.0 is returned.
AlphaComposite.public int getRule()
AlphaComposite.
AlphaComposite.public int hashCode()
hashCode in class ObjectObject.equals(java.lang.Object),
Hashtablepublic boolean equals(Object obj)
AlphaComposite.
The result is true if and only if
the argument is not null and is an
AlphaComposite object that has the same
compositing rule and alpha value as this object.
equals in class Objectobj - the Object to test for equality
true if obj equals this
AlphaComposite; false otherwise.Object.hashCode(),
Hashtable
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JavaTM 2 Platform Std. Ed. v1.4.2 |
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Copyright 2003 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.