Update of /cvsroot/squeak/squeak/platforms/win32/extras/3.4.3
In directory sc8-pr-cvs1:/tmp/cvs-serv15601
Added Files:
BBCompositing.cs
Log Message:
fix needed but not in image
--- NEW FILE: BBCompositing.cs ---
'From Squeak3.4 of 1 March 2003 [latest update: #5170] on 6 April 2003 at 7:05:25 pm'!
!BitBltSimulation methodsFor: 'combination rules' stamp: 'ar 4/6/2003 18:52'!
alphaBlend: sourceWord with: destinationWord
"Blend sourceWord with destinationWord, assuming both are 32-bit pixels.
The source is assumed to have 255*alpha in the high 8 bits of each pixel,
while the high 8 bits of the destinationWord will be ignored.
The blend produced is alpha*source + (1-alpha)*dest, with
the computation being performed independently on each color
component. The high byte of the result will be 0."
| alpha unAlpha colorMask result blend shift |
self inline: false.
alpha _ sourceWord >> 24. "High 8 bits of source pixel"
alpha = 0 ifTrue: [ ^ destinationWord ].
alpha = 255 ifTrue: [ ^ sourceWord ].
unAlpha _ 255 - alpha.
colorMask _ 16rFF.
result _ 0.
"red"
shift := 0.
blend := ((sourceWord >> shift bitAnd: colorMask) * alpha) +
((destinationWord>>shift bitAnd: colorMask) * unAlpha)
+ 254 // 255 bitAnd: colorMask.
result _ result bitOr: blend << shift.
"green"
shift := 8.
blend := ((sourceWord >> shift bitAnd: colorMask) * alpha) +
((destinationWord>>shift bitAnd: colorMask) * unAlpha)
+ 254 // 255 bitAnd: colorMask.
result _ result bitOr: blend << shift.
"blue"
shift := 16.
blend := ((sourceWord >> shift bitAnd: colorMask) * alpha) +
((destinationWord>>shift bitAnd: colorMask) * unAlpha)
+ 254 // 255 bitAnd: colorMask.
result _ result bitOr: blend << shift.
"alpha (pre-multiplied)"
shift := 24.
blend := (alpha * 255) +
((destinationWord>>shift bitAnd: colorMask) * unAlpha)
+ 254 // 255 bitAnd: colorMask.
result _ result bitOr: blend << shift.
^ result
! !
|
