html5-canvas Navigating along a Path Finding points along a line
Example
This example finds an array of approximately evenly spaced points along a line.
It decomposes Path segments created with context.lineTo into points along that line.
// Return: an array of approximately evenly spaced points along a line
//
// pxTolerance: approximate spacing allowed between points
// Ax,Ay,Bx,By: end points defining the line
//
function plotLine(pxTolerance,Ax,Ay,Bx,By){
var dx=Bx-Ax;
var dy=By-Ay;
var ptCount=parseInt(Math.sqrt(dx*dx+dy*dy))*3;
var lastX=-10000;
var lastY=-10000;
var pts=[{x:Ax,y:Ay}];
for(var i=1;i<=ptCount;i++){
var t=i/ptCount;
var x=Ax+dx*t;
var y=Ay+dy*t;
var dx1=x-lastX;
var dy1=y-lastY;
if(dx1*dx1+dy1*dy1>pxTolerance){
pts.push({x:x,y:y});
lastX=x;
lastY=y;
}
}
pts.push({x:Bx,y:By});
return(pts);
}
