Color subclass:#TranslucentColor
	instanceVariableNames:'alpha'
	classVariableNames:''
	poolDictionaries:''
	category:'Graphics-Support'
!

!TranslucentColor class methodsFor:'documentation'!

documentation
"
    TranslucentColor represents colors with an alpha (transparency)
    channel.
    This is experimental and not yet used by the system.

    [Instance variables:]

      alpha           <Integer>       the alpha value (0..255)
"


! !

!TranslucentColor class methodsFor:'instance creation'!

red:r green:g blue:b alpha:alpha
    alpha = 1 ifTrue:[
        ^ super red:r green:g blue:b
    ].
    ^ (super 
           scaledRed:(r * MaxValue // 100)
           scaledGreen:(g * MaxValue // 100)
           scaledBlue:(b * MaxValue // 100)) alpha:alpha

! !

!TranslucentColor methodsFor:'accessing'!

alpha
    "return the alpha value (0..1),
     where 0 is completely transparent and 1 is completely opaque"

    ^ alpha asFloat / 255.0


!

alpha:alphaFraction
    "set the alpha value (0..1),
     where 0 is completely transparent and 1 is completely opaque"

    alpha := (alphaFraction * 255) rounded


!

setAlphaByte:aByteValuedInteger
    "set the alpha value (0..255),
     where 0 is completely transparent and 255 is completely opaque"

    alpha := aByteValuedInteger


! !

!TranslucentColor methodsFor:'printing & storing'!

storeOn:aStream
    "append a string representing an expression to reconstruct the receiver
     to the argument, aStream"

    |clsName|

    clsName := self class name.

    aStream nextPutAll:'(' , clsName , ' red:'.
    (self red) storeOn:aStream.
    aStream nextPutAll:' green:'.
    (self green) storeOn:aStream.
    aStream nextPutAll:' blue:'.
    (self blue) storeOn:aStream.
    aStream nextPutAll:' alpha:'.
    (self alpha) storeOn:aStream.
    aStream nextPut:$).

    "
     (self red:100 green:100 blue:0 alpha:1) storeOn:Transcript
    "
! !

!TranslucentColor methodsFor:'queries'!

isOpaque
    "return true, if I represent an opaque color"

    ^ alpha == 255

!

isTranslucent
    "return true, if I represent a translucent color;
     that is: not completely opaque"

    ^ alpha < 255

!

isTransparent
    "return true, if I represent a completely transparent color"

    ^ alpha == 0
! !

!TranslucentColor class methodsFor:'documentation'!

version
    ^ '$Header: /cvs/stx/stx/libview/TranslucentColor.st,v 1.1 1999-10-06 16:06:56 cg Exp $'
! !