The RgbAlphaSub() function performs an Alpha subtraction between the RGB channels of two colours. If any channel underflows ( the result after the subtraction is lower than 0), then result is clipped to the minimum value of 0.
FACTS:
* You can find some more detailed examples in the Projects/Examples/Colours folder of your PB installation.
Mini Tutorial:
This example shows the effects of the various Alpha colour operations
ColourA=RGB(100,110,120)
ColourB=RGB(50,60,70)
PrintHEading("Rgb Alpha Addition")
PrintColour( ColourA)
PrintColour( ColourB)
PrintColour( RgbAlphaAdd(ColourA,ColourB))
PrintHEading("Rgb Alpha SubTract")
PrintColour( ColourA)
PrintColour( ColourB)
PrintColour( RgbAlphaSub(ColourA,ColourB))
PrintHEading("Rgb Alpha Mult")
PrintColour( ColourA)
PrintColour( ColourB)
PrintColour( RgbAlphaMult(ColourA,ColourB))
PrintHEading("Rgb Alpha And")
PrintColourHex( ColourA)
PrintColourHex( ColourB)
PrintColourHex( RgbAlphaAnd(ColourA,ColourB))
PrintHEading("Rgb Result After Alpha OR")
PrintColourHex( ColourA)
PrintColourHex( ColourB)
PrintColourHex( RgbAlphaOr(ColourA,ColourB))
PrintHEading("Rgb Result After Alpha XOR")
PrintColourHex( ColourA)
PrintColourHex( ColourB)
PrintColourHex( RgbAlphaXor(ColourA,ColourB))
Sync
WaitKey
; Split the colour into and R,G,B fields and display it
Function PrintColour(ThisColour)
r=RgbR(ThisCOlour)
g=RgbG(ThisCOlour)
b=RgbB(ThisCOlour)
Print Str$(r)+","+Str$(g)+","+Str$(b)
EndFunction
; Show Colour in hex
Function PrintColourHex(ThisColour)
r$=Right$(Hex$(RgbR(ThisCOlour)),2)
g$=Right$(Hex$(RgbG(ThisCOlour)),2)
b$=Right$(Hex$(RgbB(ThisCOlour)),2)
Print r$+","+g$+","+b$
EndFunction
; Display a heading
Function PrintHEading(Heading$)
Print ""
Print AutoCaps$(Heading$)
EndFunction
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This example would output.
RGB Alpha Addition
100,110,120
50,60,70
150,170,190
RGB Alpha Subtract
100,110,120
50,60,70
50,50,50
RGB Alpha Mult
100,110,120
50,60,70
19,26,33
RGB Alpha And
64,6E,78
32,3C,46
20,2C,40
RGB Result After Alpha Or
64,6E,78
32,3C,46
76,7E,7E
RGB Result After Alpha Xor
64,6E,78
32,3C,46
56,52,3E
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