; Anti-aliased lines demo & routine. By Mike Keith, Feb 2002
;
; To use anti-aliased lines in your program, just take the two lines below (between ===),
; which set up a 256-byte lookup table, and the two functions after End.
;
; AntiLine(x1,y1,x2,y2) draws a line from (x1,y1) to (x2,y2) in the
; current drawing color to the currently selected buffer.
;
; You can Lock and Unlock the buffer used (before and after batches of calls to AntiLine)
; to gain some additional speed, as is done in the sample code below, which draws
; the same pattern using regular and anti-aliased lines, so you can see the visual difference.
Graphics 800,600,32,1
;==================================================
; Lookup table required for Anti-aliased line routine.
Dim AlineTable%(64)
InitAlineTable ; You MUST do this once to initialize table
;==================================================
SetBuffer BackBuffer()
For y=0 To 599
z = y*255/599
Color z/2,z/3,0
Line 0,y,799,y
Next
Color 0,255,255
t1 = MilliSecs()
For i=0 To 360 Step 5
dx = 150*Sin(i)
dy = 150*Cos(i)
Line 160+dx,300+dy,160-dx,300-dy
Next
t2 = MilliSecs()
Color 0,0,0
Text 50,535,"Regular lines"
Text 50,550,"Took "+Str$(t2-t1)+" ms"
If 1
LockBuffer BackBuffer()
Color 0,255,255
t3 = MilliSecs()
For i=0 To 360 Step 5
dx = 150*Sin(i)
dy = 150*Cos(i)
AntiLine(600+dx,300+dy,600-dx,300-dy)
Next
t4 = MilliSecs()
UnlockBuffer BackBuffer()
EndIf
Color 0,0,0
Text 500,535,"Anti-aliased lines"
Text 500,550,"Took "+Str$(t4-t3)+" ms"
Flip
While Not(KeyHit(1))
Wend
End
;=========================================================
; Here are the actual Anti-aliased line functions
;--------------------------------------------------------------------------
Function AntiLine(x1%, y1%, x2%, y2%)
xd = x2-x1
yd = y2-y1
If (xd = 0 Or yd = 0)
Line(x1,y1,x2,y2)
Return
EndIf
r = ColorRed() Shl 16
g = ColorGreen() Shl 8
b = ColorBlue()
WritePixel x1,y1,r+g+b
WritePixel x2,y2,r+g+b
If (Abs(xd) > Abs(yd))
If (x1 > x2)
tmp = x1: x1 = x2: x2 = tmp
tmp = y1: y1 = y2: y2 = tmp
xd = x2-x1
yd = y2-y1
EndIf
grad = yd*65536/xd
yf = y1*65536
For x=x1+1 To x2-1
yf = yf + grad
w = (yf Sar 10) And $3f
y = yf Sar 16
MergePixel(x,y,r,g,b,63-w)
MergePixel(x,y+1,r,g,b,w)
Next
Else
If (y1 > y2)
tmp = x1: x1 = x2: x2 = tmp
tmp = y1: y1 = y2: y2 = tmp
xd = x2-x1
yd = y2-y1
EndIf
grad = xd*65536/yd
xf = x1*65536
For y=y1+1 To y2-1
xf = xf + grad
w = (xf Sar 10) And $3f
x = xf Sar 16
MergePixel(x,y,r,g,b,63-w)
MergePixel(x+1,y,r,g,b,w)
Next
EndIf
End Function
;--------------------------------------------------------------------------
Function MergePixel(x,y,r,g,b,w)
w = AlineTable(w)
pix = ReadPixel(x,y)
ro = pix And $ff0000
go = pix And $ff00
bo = pix And $ff
rnew = (ro + ((w*(r-ro)) Sar 8)) And $ff0000
gnew = (go + ((w*(g-go)) Sar 8)) And $ff00
bnew = bo + ((w*(b-bo)) Sar 8)
WritePixel x,y,rnew+gnew+bnew
End Function
;--------------------------------------------------------------------------
Function InitAlineTable()
For i=0 To 63
ALineTable(i) = (Sqr(Float(4*i))*16)*.4 + (4*i)*.6
Next
End Function |
