Script Library: bresenham.r

Script Library: 1238 scripts
bresenham.r

REBOL [
    title:      "Bresenham Line"
    file:       %bresenham.r
    author:     "Semseddin (Endo) Moldibi"
    version:    1.0.0
    date:       2010-08-08
    purpose:    "Returns all pairs in a block for line specified by P0/P1."
    Library: [
        level: 'beginner
        platform: 'all
        type: 'function
        domain: 'math
        tested-under: none
        support: "semseddin/at/gmail.com"
        license: 'public-domain
        see-also: none
    ]
]

BresenhamLine: funct [p0 [pair!] p1 [pair!]] [
    result: make block! 32

    if p0 = p1 [return append result p0]

    x0: p0/x x1: p1/x
    y0: p0/y y1: p1/y

    steep: greater? abs (y1 - y0) abs (x1 - x0)
    if steep [
        t: x0   x0: y0  y0: t
        t: x1   x1: y1  y1: t
    ]
    if x0 > x1 [
        t: x0   x0: x1  x1: t
        t: y0   y0: y1  y1: t
    ]
    deltax: x1 - x0
    deltay: abs (y1 - y0)
    error: 0
    deltaerr: deltay / deltax
    ystep: either y0 < y1 [1] [-1]
    y: y0
    for x x0 x1 1 [
        p: either steep [as-pair y x] [as-pair x y]
        append result p
        error: error + deltaerr
        if error >= 0.5 [
            y: y + ystep
            error: error - 1.0
        ]
    ]
    result
]

;probe BresenhamLine 13x5 25x17
;halt