/**
* Flot plugin that provides spline interpolation for line graphs
* author: Alex Bardas < alex.bardas@gmail.com >
* modified by: Avi Kohn https://github.com/AMKohn
* based on the spline interpolation described at:
* http://scaledinnovation.com/analytics/splines/aboutSplines.html
*
* Example usage: (add in plot options series object)
* for linespline:
* series: {
* ...
* lines: {
* show: false
* },
* splines: {
* show: true,
* tension: x, (float between 0 and 1, defaults to 0.5),
* lineWidth: y (number, defaults to 2),
* fill: z (float between 0 .. 1 or false, as in flot documentation)
* },
* ...
* }
* areaspline:
* series: {
* ...
* lines: {
* show: true,
* lineWidth: 0, (line drawing will not execute)
* fill: x, (float between 0 .. 1, as in flot documentation)
* ...
* },
* splines: {
* show: true,
* tension: 0.5 (float between 0 and 1)
* },
* ...
* }
*
*/
(function($) {
'use strict'
/**
* @param {Number} x0, y0, x1, y1: coordinates of the end (knot) points of the segment
* @param {Number} x2, y2: the next knot (not connected, but needed to calculate p2)
* @param {Number} tension: control how far the control points spread
* @return {Array}: p1 -> control point, from x1 back toward x0
* p2 -> the next control point, returned to become the next segment's p1
*
* @api private
*/
function getControlPoints(x0, y0, x1, y1, x2, y2, tension) {
var pow = Math.pow,
sqrt = Math.sqrt,
d01, d12, fa, fb, p1x, p1y, p2x, p2y;
// Scaling factors: distances from this knot to the previous and following knots.
d01 = sqrt(pow(x1 - x0, 2) + pow(y1 - y0, 2));
d12 = sqrt(pow(x2 - x1, 2) + pow(y2 - y1, 2));
fa = tension * d01 / (d01 + d12);
fb = tension - fa;
p1x = x1 + fa * (x0 - x2);
p1y = y1 + fa * (y0 - y2);
p2x = x1 - fb * (x0 - x2);
p2y = y1 - fb * (y0 - y2);
return [p1x, p1y, p2x, p2y];
}
var line = [];
function drawLine(points, ctx, height, fill, seriesColor) {
var c = $.color.parse(seriesColor);
c.a = typeof fill == "number" ? fill : .3;
c.normalize();
c = c.toString();
ctx.beginPath();
ctx.moveTo(points[0][0], points[0][1]);
var plength = points.length;
for (var i = 0; i < plength; i++) {
ctx[points[i][3]].apply(ctx, points[i][2]);
}
ctx.stroke();
ctx.lineWidth = 0;
ctx.lineTo(points[plength - 1][0], height);
ctx.lineTo(points[0][0], height);
ctx.closePath();
if (fill !== false) {
ctx.fillStyle = c;
ctx.fill();
}
}
/**
* @param {Object} ctx: canvas context
* @param {String} type: accepted strings: 'bezier' or 'quadratic' (defaults to quadratic)
* @param {Array} points: 2 points for which to draw the interpolation
* @param {Array} cpoints: control points for those segment points
*
* @api private
*/
function queue(ctx, type, points, cpoints) {
if (type === void 0 || (type !== 'bezier' && type !== 'quadratic')) {
type = 'quadratic';
}
type = type + 'CurveTo';
if (line.length == 0) line.push([points[0], points[1], cpoints.concat(points.slice(2)), type]);
else if (type == "quadraticCurveTo" && points.length == 2) {
cpoints = cpoints.slice(0, 2).concat(points);
line.push([points[0], points[1], cpoints, type]);
}
else line.push([points[2], points[3], cpoints.concat(points.slice(2)), type]);
}
/**
* @param {Object} plot
* @param {Object} ctx: canvas context
* @param {Object} series
*
* @api private
*/
function drawSpline(plot, ctx, series) {
// Not interested if spline is not requested
if (series.splines.show !== true) {
return;
}
var cp = [],
// array of control points
tension = series.splines.tension || 0.5,
idx, x, y, points = series.datapoints.points,
ps = series.datapoints.pointsize,
plotOffset = plot.getPlotOffset(),
len = points.length,
pts = [];
line = [];
// Cannot display a linespline/areaspline if there are less than 3 points
if (len / ps < 4) {
$.extend(series.lines, series.splines);
return;
}
for (idx = 0; idx < len; idx += ps) {
x = points[idx];
y = points[idx + 1];
if (x == null || x < series.xaxis.min || x > series.xaxis.max || y < series.yaxis.min || y > series.yaxis.max) {
continue;
}
pts.push(series.xaxis.p2c(x) + plotOffset.left, series.yaxis.p2c(y) + plotOffset.top);
}
len = pts.length;
// Draw an open curve, not connected at the ends
for (idx = 0; idx < len - 2; idx += 2) {
cp = cp.concat(getControlPoints.apply(this, pts.slice(idx, idx + 6).concat([tension])));
}
ctx.save();
ctx.strokeStyle = series.color;
ctx.lineWidth = series.splines.lineWidth;
queue(ctx, 'quadratic', pts.slice(0, 4), cp.slice(0, 2));
for (idx = 2; idx < len - 3; idx += 2) {
queue(ctx, 'bezier', pts.slice(idx, idx + 4), cp.slice(2 * idx - 2, 2 * idx + 2));
}
queue(ctx, 'quadratic', pts.slice(len - 2, len), [cp[2 * len - 10], cp[2 * len - 9], pts[len - 4], pts[len - 3]]);
drawLine(line, ctx, plot.height() + 10, series.splines.fill, series.color);
ctx.restore();
}
$.plot.plugins.push({
init: function(plot) {
plot.hooks.drawSeries.push(drawSpline);
},
options: {
series: {
splines: {
show: false,
lineWidth: 2,
tension: 0.5,
fill: false
}
}
},
name: 'spline',
version: '0.8.2'
});
})(jQuery);
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