Seperating $AARRGGBB into r,g,b

BlitzMax Forums/BlitzMax Beginners Area/Seperating $AARRGGBB into r,g,b

Simon S

(Posted 2005) [#1]

Agh! Only a short time away from coding and it seems I've forgotten everything I knew.

I'm trying to seperate a 32 bit integer from a read pixel into seperate rgb. I thought it went something like this.

r=(rgb shr 16) and $FF
g=(rgb shr 8) and $FF
b=(rgb) and $FF

Which gets me the r,g,b from the integer represting $AARRGGBB
But no, r,g,b just returns $FF everytime, regardless of the contents of rgb. I thought using AND meant it only return the last 8 bits, but apparently not.

I'm at a bit of a loss it seems. Any help, or a refresher on bitwise operations would be greatly appreciated.

Dreamora

(Posted 2005) [#2]

and and or are only logical operators in BM
You need to use & and | in BM as well as ~ for not as it is mentioned in the help

Snarty

(Posted 2005) [#3]

Try

r=(rgb & $FF0000) shr 16
g=(rgb & $FF00) shr 8
b=(rgb & $FF)

Notice the & instead of "And", this is important.

Perturbatio

(Posted 2005) [#4]

. beaten to it

Yan	(Posted 2005) [#5]

A tad confusingly, ~ is the bitwise XOR operator too.

A ~ B = A XOR B
     _
~A = A

Simon S

(Posted 2005) [#6]

Ah righto. Thanks for the help folks

N	(Posted 2005) [#7]

Here's a fun one.

Local MyColor:Int = $FFAA00BB

Local bytes:Byte Ptr = Varptr MyColor
Local alpha:Int = bytes[0]
Local red:Int = bytes[1]
Local green:Int = bytes[2]
Local blue:Int = bytes[3]

Snarty

(Posted 2005) [#8]

More Fun and games :)

RGB=$FF00AABB

Type RGBQUAD

	Field Blue:Byte
	Field Green:Byte
	Field Red:Byte
	Field Alpha:Byte
	
End Type

RGBq:RGBQUAD=New RGBQUAD

MemCopy Varptr(RGBq.Blue), Varptr(RGB), 4

Print RGBq.Alpha
Print RGBq.Red
Print RGBq.Green
Print RGBq.Blue

N	(Posted 2005) [#9]

Type RGBQuad
	Field Blue:Byte
	Field Green:Byte
	Field Red:Byte
	Field Alpha:Byte
	
	' And for more and more fun:
	Function FromInt:RGBQuad( i:Int )
		Local r:RGBQuad = New RGBQuad
		MemCopy ( VarPtr r.Alpha, Varptr i, 4 )
		Return r
	End Function

	Method ToInt:Int( i:Int )
		Return ( Int Ptr( VarPtr Alpha ) )[0]
	End Method
End Type

Took Snarty's code a bit further for the hell of it. Encapsulation is fun.