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May 18, 2017 08:10
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Canvas + D3: 20K points with mouseover
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| license: mit |
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| <!DOCTYPE html> | |
| <html lang="en"> | |
| <head> | |
| <meta charset="UTF-8"> | |
| <title>Canvas Scatterplot</title> | |
| <meta name="viewport" content="width=device-width, initial-scale=1"> | |
| <script src="http://d3js.org/d3.v4.js"></script> | |
| <script src="https://d3js.org/d3-scale-chromatic.v1.min.js"></script> | |
| <script src="https://d3js.org/d3-scale.v1.min.js"></script> | |
| <style type="text/css"> | |
| .hiddenCanvas{ | |
| display: none; | |
| } | |
| div#tooltip { | |
| position: absolute; | |
| display: inline-block; | |
| padding: 10px; | |
| font-family: 'Open Sans' sans-serif; | |
| color: #000; | |
| background-color: #fff; | |
| border: 1px solid #999; | |
| border-radius: 2px; | |
| pointer-events: none; | |
| opacity: 0; | |
| z-index: 1; | |
| } | |
| </style> | |
| </head> | |
| <body> | |
| <div id="container"></div> | |
| <div id="tooltip"></div> | |
| <script type="text/javascript"> | |
| var data = []; | |
| d3.range(20000).forEach(function(el){ | |
| data.push({ x: d3.randomNormal(5,3)(), y: d3.randomNormal(5,3)(), r: d3.randomNormal(3,1)() }); | |
| }); | |
| console.log(data); | |
| var width = 1400, | |
| height = 750; | |
| // main canvas | |
| var mainCanvas = d3.select('#container') | |
| .append('canvas') | |
| .classed('mainCanvas', true) | |
| .attr('width', width) | |
| .attr('height', height); | |
| // hidden canvas | |
| var hiddenCanvas = d3.select('#container') | |
| .append('canvas') | |
| .classed('hiddenCanvas', true) | |
| .attr('width', width) | |
| .attr('height', height); | |
| var customBase = document.createElement('custom'); | |
| var custom = d3.select(customBase); // replacement of SVG | |
| // map to track color the nodes. | |
| var colorToNode = {}; | |
| // function to create new colors for picking | |
| var nextCol = 1; | |
| function genColor(){ | |
| var ret = []; | |
| if (nextCol < 16777215){ | |
| ret.push(nextCol & 0xff); //R | |
| ret.push((nextCol & 0xff00) >> 8); //G | |
| ret.push((nextCol & 0xff0000) >> 16); //B | |
| nextCol += 1; | |
| } | |
| var col = "rgb(" + ret.join(',') + ")"; | |
| return col; | |
| } | |
| var x = d3.scaleLinear() | |
| .domain([2, 8]) | |
| .range([0, width]); | |
| var y = d3.scaleLinear() | |
| .domain([2,8]) | |
| .range([height, 0]); | |
| databind(data, x, y); | |
| var t = d3.timer(function(elapsed){ | |
| draw(mainCanvas, false); | |
| if (elapsed > 300) t.stop(); | |
| // timer running the draw function repeatedly for 300ms. | |
| }); | |
| function databind(data, x, y){ | |
| var join = custom.selectAll('custon.circle') | |
| .data(data); | |
| var enterSel = join.enter() | |
| .append('custom') | |
| .attr('class', 'circle') | |
| .attr('x', function(d,i){ | |
| return x(d.x); | |
| }) | |
| .attr('y', function(d,i){ | |
| return y(d.y); | |
| }) | |
| .attr('r', function(d,i){ | |
| return Math.abs(d.r); | |
| }); | |
| join | |
| .merge(enterSel) | |
| .transition() | |
| .attr('fillStyleHidden', function(d){ | |
| if (!d.hiddenCol){ | |
| d.hiddenCol = genColor(); | |
| colorToNode[d.hiddenCol] = d; | |
| } | |
| return d.hiddenCol; | |
| }); | |
| } | |
| function draw(canvas, hidden){ | |
| var context = canvas.node().getContext('2d'); | |
| context.clearRect(0, 0, width, height); | |
| var elements = custom.selectAll('custom.circle'); | |
| elements.each(function(d,i){ | |
| var node = d3.select(this); | |
| context.fillStyle = hidden ? node.attr('fillStyleHidden') : 'steelblue'; | |
| context.beginPath(); | |
| context.arc(node.attr('x'), node.attr('y'), node.attr('r'), 0, 2*Math.PI); | |
| context.fill(); | |
| }) | |
| } | |
| d3.select('.mainCanvas').on('mousemove', function(){ | |
| draw(hiddenCanvas, true); | |
| var mouseX = d3.event.layerX || d3.event.offsetX; | |
| var mouseY = d3.event.layerY || d3.event.offsety; | |
| var hiddenCtx = hiddenCanvas.node().getContext('2d'); | |
| var col = hiddenCtx.getImageData(mouseX, mouseY, 1, 1).data; | |
| var colKey = 'rgb(' + col[0] + ',' + col[1] + ',' + col[2] + ')'; | |
| var nodeData = colorToNode[colKey]; | |
| if (nodeData){ | |
| console.log(nodeData); | |
| d3.select('#tooltip') | |
| .style('opacity', 0.8) | |
| .style('top', d3.event.pageY + 5 + 'px') | |
| .style('left', d3.event.pageX + 5 + 'px') | |
| .html('x: ' + nodeData.x + '<br>' + 'y: ' + nodeData.y + '<br>' + 'radius: ' + nodeData.r); | |
| } else { | |
| d3.select('#tooltip') | |
| .style('opacity', 0); | |
| } | |
| }) | |
| </script> | |
| </body> | |
| </html> |
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L.101: custon => custom