Mathematical Line

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JL235	Created : 21 April 2008 System : Windows Language : Blitz Mathematical Line a linear equation from two points
This is some small code for calculating a line from two points. This then allows you to find the co-ordinates of any point along the line. The code first has some example usage and then the types and functions used at the bottom. It is designed so that you can simply copy and paste the library code from the bottom into your own project for use. It was written in response to this topic. ; by JL235 ; this code is free to use, ; however I do ask that you credited me ; www.SoCoder.net ; ### Example Code ### ; Click in two places on the screen and a linear line that intersects ; both points will be calculated and drawn ; Further clicking will replace the currently shown line with a new one. ; ; Press Escape to quit ; Graphics 800, 600, 0, 2 SetBuffer BackBuffer() Local p1.Point = Null, p2.Point = Null Local l.Line = Null While Not KeyDown(1) ; wait for user input If MouseHit(1) ; make the points If p1 = Null p1 = newPoint(MouseX(), MouseY()) Else p2 = newPoint(MouseX(), MouseY()) EndIf ; make the line, if we can If (Not p1 = Null) And (Not p2 = Null) If Not l = Null Delete l: l = Null EndIf l = newLine(p1, p2) Delete p1: p1 = Null Delete p2: p2 = Null EndIf EndIf ; draw the line Cls() Color 255, 255, 255 If Not l = Null drawLine(l) EndIf Flip True Wend End ; ### Line and Point code ### ; Line ; a mathematical representation of a line, it has two field ; the slope which describes angle that the line travels at and the ; yIntercept which is the value that the line naturally rests above the y-axis ; see: https://en.wikipedia.org/wiki/Line Type Line Field slope# Field yIntercept# End Type ; Point ; a point on the screen with an x and y position Type Point Field x Field y End Type ; newPoint ; creates and returns a new Point based on the given x and y values Function newPoint.Point(x, y) Local p.Point = New Point p\x = x p\y = y Return p End Function ; newLine ; creates and returns a new Line based on the given points Function newLine.Line(p1.Point, p2.Point) Local l.Line = New Line l\slope# = Float(p2\y - p1\y) / Float(p2\x - p1\x) l\yIntercept# = Float(p1\y - (p1\x * l\slope#)) Return l End Function ; lineY ; will return the y co-ordinate of the given line at the given x co-ordinate Function lineY(l.Line, x) Return Int((l\slope# * x) + l\yIntercept#) End Function ; drawLine ; draws the given line from one side of the screen to the other Function drawLine(l.Line) Line 0, lineY(l, 0), GraphicsWidth(), lineY(l, GraphicsWidth()) End Function --v

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