Xiaolin Wu's line algorithm: Difference between revisions

=={{header|PicoLisp}}==

<lang PicoLisp>(scl 2)

(de plot (Img X Y C)

(set (nth Img (*/ Y 1.0) (*/ X 1.0)) (- 100 C)) )

(de ipart (X)

(* 1.0 (/ X 1.0)) )

(de iround (X)

(ipart (+ X 0.5)) )

(de fpart (X)

(% X 1.0) )

(de rfpart (X)

(- 1.0 (fpart X)) )

(de xiaolin (Img X1 Y1 X2 Y2)

(let (DX (- X2 X1) DY (- Y2 Y1))

(use (Grad Xend Yend Xgap Xpxl1 Ypxl1 Xpxl2 Ypxl2 Intery)

(when (> (abs DY) (abs DX))

(xchg 'X1 'Y1 'X2 'Y2) )

(when (> X1 X2)

(xchg 'X1 'X2 'Y1 'Y2) )

(setq

Grad (*/ DY 1.0 DX)

Xend (iround X1)

Yend (+ Y1 (*/ Grad (- Xend X1) 1.0))

Xgap (rfpart (+ X1 0.5))

Xpxl1 Xend

Ypxl1 (ipart Yend) )

(plot Img Xpxl1 Ypxl1 (*/ (rfpart Yend) Xgap 1.0))

(plot Img Xpxl1 (+ 1.0 Ypxl1) (*/ (fpart Yend) Xgap 1.0))

(setq

Intery (+ Yend Grad)

Xend (iround X2)

Yend (+ Y2 (*/ Grad (- Xend X2) 1.0))

Xgap (fpart (+ X2 0.5))

Xpxl2 Xend

Ypxl2 (ipart Yend) )

(plot Img Xpxl2 Ypxl2 (*/ (rfpart Yend) Xgap 1.0))

(plot Img Xpxl2 (+ 1.0 Ypxl2) (*/ (fpart Yend) Xgap 1.0))

(for (X (+ Xpxl1 1.0) (>= (- Xpxl2 1.0) X) (+ X 1.0))

(plot Img X (ipart Intery) (rfpart Intery))

(plot Img X (+ 1.0 (ipart Intery)) (fpart Intery))

(inc 'Intery Grad) ) ) ) )

(let Img (make (do 90 (link (need 120 NIL 99)))) # Create image 120 x 90

(xiaolin Img 10.0 10.0 110.0 80.0) # Draw lines

(xiaolin Img 10.0 10.0 110.0 45.0)

(xiaolin Img 10.0 80.0 110.0 45.0)

(xiaolin Img 10.0 80.0 110.0 10.0)

(out "img.pgm" # Write to bitmap file

(prinl "P2")

(prinl 120 " " 90)

(prinl 100)

(mapc '((L) (mapc printsp L)) Img) ) )</lang>