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119 lines
2.6 KiB
119 lines
2.6 KiB
4 years ago
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<!DOCTYPE html>
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<html>
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<!-- source: https://bl.ocks.org/mbostock/8027637 -->
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<head>
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<meta charset="utf-8">
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<style>
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path {
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fill: none;
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stroke: #000;
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stroke-width: 8px;
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}
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line {
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fill: none;
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stroke: red;
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stroke-width: 0;
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}
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circle {
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fill: red;
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}
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rect {
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fill: none;
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cursor: crosshair;
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pointer-events: all;
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}
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</style>
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<body>
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<script src="https://d3js.org/d3.v3.min.js"></script>
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<script>
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var points = [[600,600],[600, 400],[300,300], [400, 600]];
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var width = 960,
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height = 500;
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var line = d3.svg.line()
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.interpolate("cardinal");
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var svg = d3.select("body").append("svg")
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.attr("width", width)
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.attr("height", height);
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var path = svg.append("path")
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.datum(points)
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.attr("d", line);
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var line = svg.append("line");
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var circle = svg.append("circle")
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.attr("cx", -10)
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.attr("cy", -10)
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.attr("r", 60);
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var isDown = false;
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svg.append("rect")
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.attr("width", width)
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.attr("height", height)
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.on("mousedown", function(){
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svg.on("mousemove", mousemoved);
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})
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.on("mouseup")
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function mousemoved() {
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var m = d3.mouse(this),
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p = closestPoint(path.node(), m);
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line.attr("x1", p[0]).attr("y1", p[1]).attr("x2", m[0]).attr("y2", m[1]);
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circle.attr("cx", p[0]).attr("cy", p[1]);
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}
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function closestPoint(pathNode, point) {
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var pathLength = pathNode.getTotalLength(),
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precision = 8,
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best,
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bestLength,
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bestDistance = Infinity;
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// linear scan for coarse approximation
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for (var scan, scanLength = 0, scanDistance; scanLength <= pathLength; scanLength += precision) {
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if ((scanDistance = distance2(scan = pathNode.getPointAtLength(scanLength))) < bestDistance) {
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best = scan, bestLength = scanLength, bestDistance = scanDistance;
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}
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}
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// binary search for precise estimate
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precision /= 2;
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while (precision > 0.5) {
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var before,
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after,
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beforeLength,
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afterLength,
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beforeDistance,
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afterDistance;
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if ((beforeLength = bestLength - precision) >= 0 && (beforeDistance = distance2(before = pathNode.getPointAtLength(beforeLength))) < bestDistance) {
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best = before, bestLength = beforeLength, bestDistance = beforeDistance;
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} else if ((afterLength = bestLength + precision) <= pathLength && (afterDistance = distance2(after = pathNode.getPointAtLength(afterLength))) < bestDistance) {
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best = after, bestLength = afterLength, bestDistance = afterDistance;
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} else {
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precision /= 2;
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}
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}
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best = [best.x, best.y];
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best.distance = Math.sqrt(bestDistance);
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return best;
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function distance2(p) {
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var dx = p.x - point[0],
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dy = p.y - point[1];
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return dx * dx + dy * dy;
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}
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}
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</script>
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<html>
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