A less-sophisticated alternative to Mike Bostock's Gradient Along Stroke.
Note that this version does not compute mitre joints, so sharp bends reveal the segmented nature of the "path."
Last active
November 20, 2015 05:19
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Simple Gradient Along Stroke
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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <script src="http://d3js.org/d3.v3.min.js"></script> | |
| <meta charset="utf-8"> | |
| </head> | |
| <body> | |
| <script src="script.js"></script> | |
| </body> | |
| </html> |
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| var margin = { top: 50, left: 50, bottom: 50, right: 50 }, | |
| width = window.innerWidth - margin.left - margin.right, | |
| height = window.innerHeight - margin.top - margin.bottom, | |
| vbWidth = width + margin.left + margin.right, | |
| vbHeight = height + margin.top + margin.bottom; | |
| var main = d3.select("body").append("main") | |
| .style({ width: "90%", margin: "0 auto 0 auto" }) | |
| .append("svg") | |
| .attr({ viewBox: "0 0 " + vbWidth + " " + vbHeight }) | |
| .append("g") | |
| .attr({ | |
| transform: "translate(" + [margin.left, margin.top] + ")" | |
| }); | |
| main.append("rect").attr({ | |
| width: width, height: height, fill: "none" | |
| }); | |
| var random = d3.random.normal(); | |
| var data = d3.range(10).map(function(d) { | |
| return { x: random(), y: random() }; | |
| }); | |
| var x = d3.scale.linear() | |
| .domain(d3.extent(data, function(d) { return d.x; })) | |
| .range([0, width]); | |
| var y = d3.scale.linear() | |
| .domain(d3.extent(data, function(d) { return d.y; })) | |
| .range([0, height]); | |
| var dots = main.selectAll(".dot").data(data); | |
| dots.enter().append("circle").classed("dot", true) | |
| .attr({ r: 5 }) | |
| .style({ opacity: 0.2 }) | |
| dots.attr({ | |
| cx: function(d) { return x(d.x); }, | |
| cy: function(d) { return y(d.y); } | |
| }); | |
| var line = d3.svg.line().interpolate("basis") | |
| .x(function(d) { return x(d.x); }) | |
| .y(function(d) { return y(d.y); }); | |
| var points = getPoints(line(data), 2); | |
| var segs = []; | |
| points.reduce(function(prev, curr) { | |
| segs.push({ | |
| x1: prev.x, y1: prev.y, x2: curr.x, y2: curr.y, t: curr.t | |
| }); | |
| return curr; | |
| }); | |
| var segmentContainer = main.selectAll(".segments").data([segs]); | |
| segmentContainer.enter().append("g").classed("segments", true); | |
| var segments = segmentContainer.selectAll(".segment").data(Object); | |
| segments.enter().append("line"); | |
| var i = d3.interpolateRgb("green", "red"); | |
| segments | |
| .attr({ | |
| x1: function(d) { return d.x1; }, y1: function(d) { return d.y1; }, | |
| x2: function(d) { return d.x2; }, y2: function(d) { return d.y2; }, | |
| stroke: function(d) { return i(d.t); }, | |
| "stroke-width": 10, "stroke-opacity": 0.1 | |
| }) | |
| .transition() | |
| .delay(function(d, i) { return i; }) | |
| .attr("stroke-opacity", 1); | |
| segments.exit().remove(); | |
| // Based on: //gist.github.com/mbostock/4163057 | |
| // Sample the SVG path string "d" uniformly with the specified precision. | |
| function getPoints(d, step) { | |
| var path = document.createElementNS(d3.ns.prefix.svg, "path"); | |
| path.setAttribute("d", d); | |
| var length = path.getTotalLength(); | |
| return d3.range(0, length, step) | |
| .map(function(t) { | |
| var point = path.getPointAtLength(t); | |
| return { x: point.x, y: point.y, t: t/length }; | |
| }); | |
| } |
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