Part 3, based on this medium article.
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November 1, 2018 08:20
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part 3, Zoom and Panning with D3.js and canvas
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license: mit |
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<!DOCTYPE html> | |
<head> | |
<meta charset="utf-8"> | |
<script src="https://d3js.org/d3.v4.min.js"></script> | |
<style> | |
body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; } | |
</style> | |
</head> | |
<style> | |
.scatter-container { | |
margin: auto; | |
width: 900px; | |
height: 500px; | |
} | |
.svg-plot, .canvas-plot { | |
position: absolute; | |
} | |
.tools { | |
position: absolute; | |
left: calc(50% + 400px); | |
visibility: hidden; | |
z-index:10; | |
} | |
.tools button { | |
background-color: #e7e7e7; | |
border: none; | |
color: #000000; | |
cursor: pointer; | |
display: block; | |
margin-bottom: 5px; | |
padding: 5px 10px; | |
outline: 0; | |
} | |
.tools button.active { | |
background-color: #13a613; | |
} | |
</style> | |
<body> | |
<div class="scatter-container"> | |
<div class="tools"> | |
<button id="reset">Reset</button> | |
<button id="zoom" class="active">Zoom</button> | |
<button id="brush">Brush</button> | |
</div> | |
</div> | |
<script> | |
let dataExample = []; | |
for (let i = 0; i < 10000; i++) { | |
const x = Math.floor(Math.random() * 999999) + 1; | |
const y = Math.floor(Math.random() * 999999) + 1; | |
dataExample.push([x, y]); | |
} | |
const pointColor = '#3585ff' | |
const margin = { top: 20, right: 15, bottom: 60, left: 70 }; | |
const outerWidth = 900; | |
const outerHeight = 500; | |
const width = outerWidth - margin.left - margin.right; | |
const height = outerHeight - margin.top - margin.bottom; | |
const container = d3.select('.scatter-container'); | |
let lastTransform = null; | |
// Init SVG | |
const svgChart = container.append('svg:svg') | |
.attr('width', outerWidth) | |
.attr('height', outerHeight) | |
.attr('class', 'svg-plot') | |
.append('g') | |
.attr('transform', `translate(${margin.left}, ${margin.top})`); | |
// Init Canvas | |
const canvasChart = container.append('canvas') | |
.attr('width', width) | |
.attr('height', height) | |
.style('margin-left', margin.left + 'px') | |
.style('margin-top', margin.top + 'px') | |
.attr('class', 'canvas-plot'); | |
// Prepare buttons | |
const toolsList = container.select('.tools') | |
.style('margin-top', margin.top + 'px') | |
.style('visibility', 'visible'); | |
toolsList.select('#reset').on('click', () => { | |
const t = d3.zoomIdentity.translate(0, 0).scale(1); | |
canvasChart.transition() | |
.duration(200) | |
.ease(d3.easeLinear) | |
.call(zoom_function.transform, t) | |
}); | |
const context = canvasChart.node().getContext('2d'); | |
// Init Scales | |
const x = d3.scaleLinear().domain([0, d3.max(dataExample, (d) => d[0])]).range([0, width]).nice(); | |
const y = d3.scaleLinear().domain([0, d3.max(dataExample, (d) => d[1])]).range([height, 0]).nice(); | |
// Init Axis | |
const xAxis = d3.axisBottom(x); | |
const yAxis = d3.axisLeft(y); | |
// Add Axis | |
const gxAxis = svgChart.append('g') | |
.attr('transform', `translate(0, ${height})`) | |
.call(xAxis); | |
const gyAxis = svgChart.append('g') | |
.call(yAxis); | |
// Add labels | |
svgChart.append('text') | |
.attr('x', `-${height / 2}`) | |
.attr('dy', '-3.5em') | |
.attr('transform', 'rotate(-90)') | |
.text('Axis Y'); | |
svgChart.append('text') | |
.attr('x', `${width / 2}`) | |
.attr('y', `${height + 40}`) | |
.text('Axis X'); | |
// Draw plot on canvas | |
function draw(transform) { | |
lastTransform = transform; | |
const scaleX = transform.rescaleX(x); | |
const scaleY = transform.rescaleY(y); | |
gxAxis.call(xAxis.scale(scaleX)); | |
gyAxis.call(yAxis.scale(scaleY)); | |
context.clearRect(0, 0, width, height); | |
dataExample.forEach(point => { | |
drawPoint(scaleX, scaleY, point, transform.k); | |
}); | |
} | |
// Initial draw made with no zoom | |
draw(d3.zoomIdentity) | |
function drawPoint(scaleX, scaleY, point, k) { | |
context.beginPath(); | |
context.fillStyle = pointColor; | |
const px = scaleX(point[0]); | |
const py = scaleY(point[1]); | |
context.arc(px, py, 1.2 * k, 0, 2 * Math.PI, true); | |
context.fill(); | |
} | |
// Zoom/Drag handler | |
const zoom_function = d3.zoom().scaleExtent([1, 1000]) | |
.on('zoom', () => { | |
const transform = d3.event.transform; | |
context.save(); | |
draw(transform); | |
context.restore(); | |
}); | |
canvasChart.call(zoom_function); | |
//Box Zoom | |
const svgChartParent = d3.select('svg'); | |
const zoomButton = toolsList.select('#zoom').on('click', () => { | |
toolsList.selectAll('.active').classed('active', false); | |
zoomButton.classed('active', true); | |
canvasChart.style('z-index', 1); | |
svgChartParent.style('z-index', 0); | |
}); | |
const brushButton = toolsList.select('#brush').on('click', () => { | |
toolsList.selectAll('.active').classed('active', false); | |
brushButton.classed('active', true); | |
canvasChart.style('z-index', 0); | |
svgChartParent.style('z-index', 1); | |
}); | |
const brush = d3.brush().extent([[0, 0], [width, height]]) | |
.on("start", () => { brush_startEvent(); }) | |
.on("brush", () => { brush_brushEvent(); }) | |
.on("end", () => { brush_endEvent(); }) | |
.on("start.nokey", function() { | |
d3.select(window).on("keydown.brush keyup.brush", null); | |
}); | |
const brushSvg = svgChart | |
.append("g") | |
.attr("class", "brush") | |
.call(brush); | |
let brushStartPoint = null; | |
function brush_startEvent() { | |
const sourceEvent = d3.event.sourceEvent; | |
const selection = d3.event.selection; | |
if (sourceEvent.type === 'mousedown') { | |
brushStartPoint = { | |
mouse: { | |
x: sourceEvent.screenX, | |
y: sourceEvent.screenY | |
}, | |
x: selection[0][0], | |
y: selection[0][1] | |
} | |
} else { | |
brushStartPoint = null; | |
} | |
} | |
function brush_brushEvent() { | |
if (brushStartPoint !== null) { | |
const scale = width / height; | |
const sourceEvent = d3.event.sourceEvent; | |
const mouse = { | |
x: sourceEvent.screenX, | |
y: sourceEvent.screenY | |
}; | |
if (mouse.x < 0) { mouse.x = 0; } | |
if (mouse.y < 0) { mouse.y = 0; } | |
let distance = mouse.y - brushStartPoint.mouse.y; | |
let yPosition = brushStartPoint.y + distance; | |
let xCorMulti = 1; | |
if ((distance < 0 && mouse.x > brushStartPoint.mouse.x) || (distance > 0 && mouse.x < brushStartPoint.mouse.x)) { | |
xCorMulti = -1; | |
} | |
if (yPosition > height) { | |
distance = height - brushStartPoint.y; | |
yPosition = height; | |
} else if (yPosition < 0) { | |
distance = -brushStartPoint.y; | |
yPosition = 0; | |
} | |
let xPosition = brushStartPoint.x + distance * scale * xCorMulti; | |
const oldDistance = distance; | |
if (xPosition > width) { | |
distance = (width - brushStartPoint.x) / scale; | |
xPosition = width; | |
} else if (xPosition < 0) { | |
distance = brushStartPoint.x / scale; | |
xPosition = 0; | |
} | |
if (oldDistance !== distance) { | |
distance *= (oldDistance < 0) ? -1 : 1; | |
yPosition = brushStartPoint.y + distance; | |
} | |
const selection = svgChart.select(".selection"); | |
const posValue = Math.abs(distance); | |
selection.attr('width', posValue * scale).attr('height', posValue); | |
if (xPosition < brushStartPoint.x) { | |
selection.attr('x', xPosition); | |
} | |
if (yPosition < brushStartPoint.y) { | |
selection.attr('y', yPosition); | |
} | |
const minX = Math.min(brushStartPoint.x, xPosition); | |
const maxX = Math.max(brushStartPoint.x, xPosition); | |
const minY = Math.min(brushStartPoint.y, yPosition); | |
const maxY = Math.max(brushStartPoint.y, yPosition); | |
lastSelection = { x1: minX, x2: maxX, y1: minY, y2: maxY }; | |
} | |
} | |
function brush_endEvent() { | |
const s = d3.event.selection; | |
if (!s && lastSelection !== null) { | |
// Re-scale axis for the last transformation | |
let zx = lastTransform.rescaleX(x); | |
let zy = lastTransform.rescaleY(y); | |
// Calc distance on Axis-X to use in scale | |
let totalX = Math.abs(lastSelection.x2 - lastSelection.x1); | |
// Get current point [x,y] on canvas | |
const originalPoint = [zx.invert(lastSelection.x1), zy.invert(lastSelection.y1)]; | |
// Calc scale mapping distance AxisX in width * k | |
// Example: Scale 1, width: 830, totalX: 415 | |
// Result in a zoom of 2 | |
const t = d3.zoomIdentity.scale(((width * lastTransform.k) / totalX)); | |
// Re-scale axis for the new transformation | |
zx = t.rescaleX(x); | |
zy = t.rescaleY(y); | |
// Call zoomFunction with a new transformation from the new scale and brush position. | |
// To calculate the brush position we use the originalPoint in the new Axis Scale. | |
// originalPoint it's always positive (because we're sure it's within the canvas). | |
// We need to translate this originalPoint to [0,0]. So, we do (0 - position) or (position * -1) | |
canvasChart | |
.transition() | |
.duration(200) | |
.ease(d3.easeLinear) | |
.call(zoom_function.transform, | |
d3.zoomIdentity | |
.translate(zx(originalPoint[0]) * -1, zy(originalPoint[1]) * -1) | |
.scale(t.k)); | |
lastSelection = null; | |
} else { | |
brushSvg.call(brush.move, null); | |
} | |
} | |
</script> | |
</body> |
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