Canvas Charts and Diagrams
Pie Chart with Demo
<!doctype html>
<html>
<head>
<style>
body {
background-color: white;
}
#canvas {
border: 1px solid red;
}
</style>
<script>
window.onload = (function() {
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
ctx.lineWidth = 2;
ctx.font = '14px verdana';
var PI2 = Math.PI * 2;
var myColor = ["Green", "Red", "Blue"];
var myData = [30, 60, 10];
var cx = 150;
var cy = 150;
var radius = 100;
pieChart(myData, myColor);
function pieChart(data, colors) {
var total = 0;
for (var i = 0; i < data.length; i++) {
total += data[i];
}
var sweeps = []
for (var i = 0; i < data.length; i++) {
sweeps.push(data[i] / total * PI2);
}
var accumAngle = 0;
for (var i = 0; i < sweeps.length; i++) {
drawWedge(accumAngle, accumAngle + sweeps[i], colors[i], data[i]);
accumAngle += sweeps[i];
}
}
function drawWedge(startAngle, endAngle, fill, label) {
// draw the wedge
ctx.beginPath();
ctx.moveTo(cx, cy);
ctx.arc(cx, cy, radius, startAngle, endAngle, false);
ctx.closePath();
ctx.fillStyle = fill;
ctx.strokeStyle = 'black';
ctx.fill();
ctx.stroke();
// draw the label
var midAngle = startAngle + (endAngle - startAngle) / 2;
var labelRadius = radius * .65;
var x = cx + (labelRadius) * Math.cos(midAngle);
var y = cy + (labelRadius) * Math.sin(midAngle);
ctx.fillStyle = 'white';
ctx.fillText(label, x, y);
}
}); // end $(function(){});
</script>
</head>
<body>
<canvas id="canvas" width=512 height=512></canvas>
</body>
</html>
Line with arrowheads
// Usage:
drawLineWithArrows(50, 50, 150, 50, 5, 8, true, true);
// x0,y0: the line's starting point
// x1,y1: the line's ending point
// width: the distance the arrowhead perpendicularly extends away from the line
// height: the distance the arrowhead extends backward from the endpoint
// arrowStart: true/false directing to draw arrowhead at the line's starting point
// arrowEnd: true/false directing to draw arrowhead at the line's ending point
function drawLineWithArrows(x0, y0, x1, y1, aWidth, aLength, arrowStart, arrowEnd) {
var dx = x1 - x0;
var dy = y1 - y0;
var angle = Math.atan2(dy, dx);
var length = Math.sqrt(dx * dx + dy * dy);
//
ctx.translate(x0, y0);
ctx.rotate(angle);
ctx.beginPath();
ctx.moveTo(0, 0);
ctx.lineTo(length, 0);
if (arrowStart) {
ctx.moveTo(aLength, -aWidth);
ctx.lineTo(0, 0);
ctx.lineTo(aLength, aWidth);
}
if (arrowEnd) {
ctx.moveTo(length - aLength, -aWidth);
ctx.lineTo(length, 0);
ctx.lineTo(length - aLength, aWidth);
}
//
ctx.stroke();
ctx.setTransform(1, 0, 0, 1, 0, 0);
}
Cubic & Quadratic Bezier curve with arrowheads
// Usage:
var p0 = {
x: 50,
y: 100
};
var p1 = {
x: 100,
y: 0
};
var p2 = {
x: 200,
y: 200
};
var p3 = {
x: 300,
y: 100
};
cubicCurveArrowHeads(p0, p1, p2, p3, 15, true, true);
quadraticCurveArrowHeads(p0, p1, p2, 15, true, true);
// or use defaults true for both ends with arrow heads
cubicCurveArrowHeads(p0, p1, p2, p3, 15);
quadraticCurveArrowHeads(p0, p1, p2, 15);
// draws both cubic and quadratic bezier
function bezWithArrowheads(p0, p1, p2, p3, arrowLength, hasStartArrow, hasEndArrow) {
var x, y, norm, ex, ey;
function pointsToNormalisedVec(p, pp) {
var len;
norm.y = pp.x - p.x;
norm.x = -(pp.y - p.y);
len = Math.sqrt(norm.x * norm.x + norm.y * norm.y);
norm.x /= len;
norm.y /= len;
return norm;
}
var arrowWidth = arrowLength / 2;
norm = {};
// defaults to true for both arrows if arguments not included
hasStartArrow = hasStartArrow === undefined || hasStartArrow === null ? true : hasStartArrow;
hasEndArrow = hasEndArrow === undefined || hasEndArrow === null ? true : hasEndArrow;
ctx.beginPath();
ctx.moveTo(p0.x, p0.y);
if (p3 === undefined) {
ctx.quadraticCurveTo(p1.x, p1.y, p2.x, p2.y);
ex = p2.x; // get end point
ey = p2.y;
norm = pointsToNormalisedVec(p1, p2);
} else {
ctx.bezierCurveTo(p1.x, p1.y, p2.x, p2.y, p3.x, p3.y)
ex = p3.x; // get end point
ey = p3.y;
norm = pointsToNormalisedVec(p2, p3);
}
if (hasEndArrow) {
x = arrowWidth * norm.x + arrowLength * -norm.y;
y = arrowWidth * norm.y + arrowLength * norm.x;
ctx.moveTo(ex + x, ey + y);
ctx.lineTo(ex, ey);
x = arrowWidth * -norm.x + arrowLength * -norm.y;
y = arrowWidth * -norm.y + arrowLength * norm.x;
ctx.lineTo(ex + x, ey + y);
}
if (hasStartArrow) {
norm = pointsToNormalisedVec(p0, p1);
x = arrowWidth * norm.x - arrowLength * -norm.y;
y = arrowWidth * norm.y - arrowLength * norm.x;
ctx.moveTo(p0.x + x, p0.y + y);
ctx.lineTo(p0.x, p0.y);
x = arrowWidth * -norm.x - arrowLength * -norm.y;
y = arrowWidth * -norm.y - arrowLength * norm.x;
ctx.lineTo(p0.x + x, p0.y + y);
}
ctx.stroke();
}
function cubicCurveArrowHeads(p0, p1, p2, p3, arrowLength, hasStartArrow, hasEndArrow) {
bezWithArrowheads(p0, p1, p2, p3, arrowLength, hasStartArrow, hasEndArrow);
}
function quadraticCurveArrowHeads(p0, p1, p2, arrowLength, hasStartArrow, hasEndArrow) {
bezWithArrowheads(p0, p1, p2, undefined, arrowLength, hasStartArrow, hasEndArrow);
}
Wedge
The code draws only the wedge ... circle drawn here for perspective only.
// Usage
var wedge = {
cx: 150,
cy: 150,
radius: 100,
startAngle: 0,
endAngle: Math.PI * .65
}
drawWedge(wedge, 'skyblue', 'gray', 4);
function drawWedge(w, fill, stroke, strokewidth) {
ctx.beginPath();
ctx.moveTo(w.cx, w.cy);
ctx.arc(w.cx, w.cy, w.radius, w.startAngle, w.endAngle);
ctx.closePath();
ctx.fillStyle = fill;
ctx.fill();
ctx.strokeStyle = stroke;
ctx.lineWidth = strokewidth;
ctx.stroke();
}
Arc with both fill and stroke
// Usage:
var arc = {
cx: 150,
cy: 150,
innerRadius: 75,
outerRadius: 100,
startAngle: -Math.PI / 4,
endAngle: Math.PI
}
drawArc(arc, 'skyblue', 'gray', 4);
function drawArc(a, fill, stroke, strokewidth) {
ctx.beginPath();
ctx.arc(a.cx, a.cy, a.innerRadius, a.startAngle, a.endAngle);
ctx.arc(a.cx, a.cy, a.outerRadius, a.endAngle, a.startAngle, true);
ctx.closePath();
ctx.fillStyle = fill;
ctx.strokeStyle = stroke;
ctx.lineWidth = strokewidth
ctx.fill();
ctx.stroke();
}
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