line.wax

;; line.wax
;; rasterize lines using simple line algorithm

(@include math)

;; datastructure for storing an image
(struct image
	(let data (arr int))
	(let w int) ; width
	(let h int) ; height
)

;; initialize an image full of zeros
(func zeros (param w int) (param h int) 
	(result (struct image))
	
	(let data (arr int) (alloc (arr int)))
	(let im (struct image) (alloc (struct image)))
	(for i 0 (< i (* w h)) 1 (do
		(insert data (# data) 0)
	))
	(set im data data)
	(set im w w)
	(set im h h)
	(return im)
)

;; read value of a pixel
(func getpixel 
	(param im (struct image))
	(param x int) (param y int)
	(result int)
	(if (||   ; boundary check
		(<  x 0) (< y 0)
		(>= x (get im w))
		(>= y (get im h))
	)(then
		(return 0)
	))
	(return 
		(get im data (+ (* y (get im w)) x))
	)
)

;; write value to a pixel
(func setpixel 
	(param im (struct image))
	(param x int) (param y int) (param v int)
	(if (||   ; boundary check
		(<  x 0) (< y 0)
		(>= x (get im w))
		(>= y (get im h))
	)(then
		(return)
	))
	(set (get im data)
		(+ (* y (get im w)) x)
		v
	)
)

;; helper for line drawing algorithm
;; compute x/y from y/x using slope
(func linestep
	(param sx0 int) (param sx1 int)
	(param sy0 int) (param sy1 int)
	(param x int)
	(result int)
	(if (= sx0 sx1) (then
		(return sy1)
	))
	(return (cast (call round
		(+ sy0 (*
			(- x sx0)
			(/ (- sy1 sy0) (cast (- sx1 sx0) float) )
		))
	) int))
)

;; raster line drawing algorithm
(func line 
	(param im (struct image))
	(param x0 float) (param y0 float) ; start pos
	(param x1 float) (param y1 float) ; end pos
	(param v int) ;color
	 
	(let sx0 int (call round x0))
	(let sy0 int (call round y0))
	(let sx1 int (call round x1))
	(let sy1 int (call round y1))
	
	(let dx int (? (> sx1 sx0) 1 -1)) ; x increment
	(let dy int (? (> sy1 sy0) 1 -1)) ; y increment
	
	(if (>=
		(call abs (- sx0 sx1))
		(call abs (- sy0 sy1))
	)(then ; slope < 1 ?
		(let x int sx0)
		(while (<> x (+ sx1 dx)) (do
			(let y int (call linestep sx0 sx1 sy0 sy1 x))
			(call setpixel im x y v)
			(set x (+ x dx))
		))
	)(else
		(let y int sy0)
		(while (<> y (+ sy1 dy)) (do
			(let x int (call linestep sy0 sy1 sx0 sx1 y))
			(call setpixel im x y v)
			(set y (+ y dy))
		))
	))
)

;; visualize the image with ASCII drawing in terminal
(func imshow (param im (struct image))
	(local s str (alloc str "+"))
	(for j 0 (< j (get im w)) 1 (do (<< s "-")))
	(<< s "+\n")
	(for i 0 (< i (get im h)) 1 (do
		(<< s "|")
		(for j 0 (< j (get im w)) 1 (do
			(<< s (+ (call getpixel im j i) 32))
		))
		(<< s "|\n")
	))
	(<< s "+")
	(for j 0 (< j (get im w)) 1 (do (<< s "-")))
	(<< s "+")
	(print s)
)

;; free allocated image
(func dispose (param im (struct image))
	(free (get im data))
	(free im)
)

(func main (result int)
	(let im (struct image) (call zeros 60 30))
	
	;; generate some random lines to draw
	(for i 0 (< i 7) 1 (do
		(let x0 float (* (call random) (get im w)))
		(let y0 float (* (call random) (get im h)))
		(let x1 float (* (call random) (get im w)))
		(let y1 float (* (call random) (get im h)))
		(let v int (+ i 1))
		(call line im x0 y0 x1 y1 v)
	))
	
	(call imshow im)
	(call dispose im)
	(return 0)
)