"{ Package: 'stx:libbasic2' }"

Geometric subclass:#CurveFitter

	instanceVariableNames:'points'

	classVariableNames:''

	poolDictionaries:''

	category:'Graphics-Geometry-Objects'

!

!CurveFitter class methodsFor:'documentation'!

documentation

"

    I represent a conic section determined by three points p1, p2 and p3. 

    I interpolate p1 and p3 and am tangent to line p1, p2 at p1 and line p3, p2 at p3.

    [see also:]

        Polygon LineSegment Circle EllipticalArc 

        Rectangle Curve Arrow Spline ArrowedSpline

    [author:]

        ?

        adapted to ST/X by Claus Gittinger

"

!

examples

"

                                                                        [exBegin]

    |v s|

    v := (View extent:100@100) openAndWait.

    v displayLineFrom:(0@20) to:(100@20).

    v displayLineFrom:(0@80) to:(100@80).

    v displayLineFrom:(0@60) to:(100@60).

    v displayLineFrom:(20@0) to:(20@100).

    v displayLineFrom:(80@0) to:(80@100).

    s := CurveFitter new points:

                (Array with:(20@20)

                       with:(80@60)

                       with:(20@80)).

'

    v paint:Color blue.

    s displayFilledOn:v.

'.

    v paint:Color red.

    s displayStrokedOn:v.

                                                                        [exEnd]

"

! !

!CurveFitter methodsFor:'accessing'!

points

    "the collection of points which are used to approximate the curve"

    ^ points 

!

points:aCollectionOfPoints

    "set the collection of points which are used to approximate the curve"

    points := aCollectionOfPoints.

! !

!CurveFitter methodsFor:'displaying'!

displayStrokedOn:aDisplayMedium 

    | pa pb k s p1 p2 p3 |

    points size < 3 ifTrue: [ self error: 'Curve must have three points' ].

    p1 := points at:1.

    p2 := points at:2.

    p3 := points at:3.

    s := Polygon new.

    s add: p1.

    pa := p2 - p1.

    pb := p3 - p2.

    k := 5 max: pa x abs + pa y abs + pb x abs + pb y abs // 20.

    "k is a guess as to how many line segments to use to approximate the curve."

    1 to: k do:[:i | 

        s add: pa * i // k + p1 * (k - i) + (pb * (i - 1) // k + p2 * (i - 1)) // (k - 1)

    ].

    s add: p3.

    s displayOn:aDisplayMedium

! !

!CurveFitter class methodsFor:'documentation'!

version_CVS

    ^ '$Header: /cvs/stx/stx/libbasic2/CurveFitter.st,v 1.1 2009-10-26 21:14:55 cg Exp $'

! !