22đź‘Ť
The code that you were trying to use is actually for chart.js v1 and, as you discovered, does not work for chart.js v2 (which is almost a full chart.js re-write).
To achieve the same results in chart.js v2, you need to extend Chart.elements.Rectangle and overwrite it’s draw method in order to paint the rounded top. There is already a chart.js helper method that will draw a rounded rectangle (Chart.helpers.drawRoundedRectangle), so we will modify it slightly and create a new helper method that will only draw a rounded top (instead of all sides).
// draws a rectangle with a rounded top
Chart.helpers.drawRoundedTopRectangle = function(ctx, x, y, width, height, radius) {
ctx.beginPath();
ctx.moveTo(x + radius, y);
// top right corner
ctx.lineTo(x + width - radius, y);
ctx.quadraticCurveTo(x + width, y, x + width, y + radius);
// bottom right corner
ctx.lineTo(x + width, y + height);
// bottom left corner
ctx.lineTo(x, y + height);
// top left
ctx.lineTo(x, y + radius);
ctx.quadraticCurveTo(x, y, x + radius, y);
ctx.closePath();
};
Chart.elements.RoundedTopRectangle = Chart.elements.Rectangle.extend({
draw: function() {
var ctx = this._chart.ctx;
var vm = this._view;
var left, right, top, bottom, signX, signY, borderSkipped;
var borderWidth = vm.borderWidth;
if (!vm.horizontal) {
// bar
left = vm.x - vm.width / 2;
right = vm.x + vm.width / 2;
top = vm.y;
bottom = vm.base;
signX = 1;
signY = bottom > top? 1: -1;
borderSkipped = vm.borderSkipped || 'bottom';
} else {
// horizontal bar
left = vm.base;
right = vm.x;
top = vm.y - vm.height / 2;
bottom = vm.y + vm.height / 2;
signX = right > left? 1: -1;
signY = 1;
borderSkipped = vm.borderSkipped || 'left';
}
// Canvas doesn't allow us to stroke inside the width so we can
// adjust the sizes to fit if we're setting a stroke on the line
if (borderWidth) {
// borderWidth shold be less than bar width and bar height.
var barSize = Math.min(Math.abs(left - right), Math.abs(top - bottom));
borderWidth = borderWidth > barSize? barSize: borderWidth;
var halfStroke = borderWidth / 2;
// Adjust borderWidth when bar top position is near vm.base(zero).
var borderLeft = left + (borderSkipped !== 'left'? halfStroke * signX: 0);
var borderRight = right + (borderSkipped !== 'right'? -halfStroke * signX: 0);
var borderTop = top + (borderSkipped !== 'top'? halfStroke * signY: 0);
var borderBottom = bottom + (borderSkipped !== 'bottom'? -halfStroke * signY: 0);
// not become a vertical line?
if (borderLeft !== borderRight) {
top = borderTop;
bottom = borderBottom;
}
// not become a horizontal line?
if (borderTop !== borderBottom) {
left = borderLeft;
right = borderRight;
}
}
// calculate the bar width and roundess
var barWidth = Math.abs(left - right);
var roundness = this._chart.config.options.barRoundness || 0.5;
var radius = barWidth * roundness * 0.5;
// keep track of the original top of the bar
var prevTop = top;
// move the top down so there is room to draw the rounded top
top = prevTop + radius;
var barRadius = top - prevTop;
ctx.beginPath();
ctx.fillStyle = vm.backgroundColor;
ctx.strokeStyle = vm.borderColor;
ctx.lineWidth = borderWidth;
// draw the rounded top rectangle
Chart.helpers.drawRoundedTopRectangle(ctx, left, (top - barRadius + 1), barWidth, bottom - prevTop, barRadius);
ctx.fill();
if (borderWidth) {
ctx.stroke();
}
// restore the original top value so tooltips and scales still work
top = prevTop;
},
});
Next, you will also have to extend the bar chart controller (Chart.controllers.bar) and overwrite dataElementType to use the new “rounded rectangle” for the chart instead of a regular rectangle.
Chart.defaults.roundedBar = Chart.helpers.clone(Chart.defaults.bar);
Chart.controllers.roundedBar = Chart.controllers.bar.extend({
dataElementType: Chart.elements.RoundedTopRectangle
});
Lastly, we will modify the chart’s config to use the new chart type created above and add a new options property called barRoundness to control how round the top is (0 is flat, 1 is a semi-circle).
var ctx = document.getElementById("canvas").getContext("2d");
var myBar = new Chart(ctx, {
type: 'roundedBar',
data: {
labels: ["Car", "Bike", "Walking"],
datasets: [{
label: 'Students',
backgroundColor: chartColors.blue,
data: [
randomScalingFactor(),
randomScalingFactor(),
randomScalingFactor(),
]
}, {
label: 'Teachers',
backgroundColor: chartColors.red,
data: [
randomScalingFactor(),
randomScalingFactor(),
randomScalingFactor(),
]
}, {
label: 'Visitors',
backgroundColor: chartColors.green,
data: [
randomScalingFactor(),
randomScalingFactor(),
randomScalingFactor(),
]
}]
},
options: {
responsive: true,
barRoundness: 1,
title: {
display: true,
text: "Chart.js - Bar Chart with Rounded Tops (drawRoundedTopRectangle Method)"
},
}
});
You can see a full working example at this codepen.
Also, in case you want a slightly different “rounded top” look, here is another codepen that uses a different approach to drawing the top (a single quadratic curve).
8đź‘Ť
The following only customizes the Chart.elements.Rectangle.prototype.draw – no need to create an entirely new chart type.
Other pros:
- It works well with both vertical & horizontal bar charts
- It works well with both vertical & horizontal stacked bar charts – it only rounds the last box in the series
Noted issue: because this only rounds the box in the last dataset, if the value of the datapoint in the last dataset is < either of the previous data points, the visual top-most box will not be rounded.
However, if the last data point is negative and the lowest value, it will round that box on the bottom corners.
Credit: original code belongs to https://github.com/uffo. Code below and linked fiddle demonstrate increasing positive values in each dataset for each stack, and also modifies some of the default radius options.
/**Customize the Rectangle.prototype draw method**/
Chart.elements.Rectangle.prototype.draw = function() {
var ctx = this._chart.ctx;
var vm = this._view;
var left, right, top, bottom, signX, signY, borderSkipped, radius;
var borderWidth = vm.borderWidth;
// If radius is less than 0 or is large enough to cause drawing errors a max
// radius is imposed. If cornerRadius is not defined set it to 0.
var cornerRadius = this._chart.config.options.cornerRadius;
var fullCornerRadius = this._chart.config.options.fullCornerRadius;
var stackedRounded = this._chart.config.options.stackedRounded;
var typeOfChart = this._chart.config.type;
if (cornerRadius < 0) {
cornerRadius = 0;
}
if (typeof cornerRadius == 'undefined') {
cornerRadius = 0;
}
if (typeof fullCornerRadius == 'undefined') {
fullCornerRadius = false;
}
if (typeof stackedRounded == 'undefined') {
stackedRounded = false;
}
if (!vm.horizontal) {
// bar
left = vm.x - vm.width / 2;
right = vm.x + vm.width / 2;
top = vm.y;
bottom = vm.base;
signX = 1;
signY = bottom > top ? 1 : -1;
borderSkipped = vm.borderSkipped || 'bottom';
} else {
// horizontal bar
left = vm.base;
right = vm.x;
top = vm.y - vm.height / 2;
bottom = vm.y + vm.height / 2;
signX = right > left ? 1 : -1;
signY = 1;
borderSkipped = vm.borderSkipped || 'left';
}
// Canvas doesn't allow us to stroke inside the width so we can
// adjust the sizes to fit if we're setting a stroke on the line
if (borderWidth) {
// borderWidth shold be less than bar width and bar height.
var barSize = Math.min(Math.abs(left - right), Math.abs(top - bottom));
borderWidth = borderWidth > barSize ? barSize : borderWidth;
var halfStroke = borderWidth / 2;
// Adjust borderWidth when bar top position is near vm.base(zero).
var borderLeft = left + (borderSkipped !== 'left' ? halfStroke * signX : 0);
var borderRight = right + (borderSkipped !== 'right' ? -halfStroke * signX : 0);
var borderTop = top + (borderSkipped !== 'top' ? halfStroke * signY : 0);
var borderBottom = bottom + (borderSkipped !== 'bottom' ? -halfStroke * signY : 0);
// not become a vertical line?
if (borderLeft !== borderRight) {
top = borderTop;
bottom = borderBottom;
}
// not become a horizontal line?
if (borderTop !== borderBottom) {
left = borderLeft;
right = borderRight;
}
}
ctx.beginPath();
ctx.fillStyle = vm.backgroundColor;
ctx.strokeStyle = vm.borderColor;
ctx.lineWidth = borderWidth;
// Corner points, from bottom-left to bottom-right clockwise
// | 1 2 |
// | 0 3 |
var corners = [
[left, bottom],
[left, top],
[right, top],
[right, bottom]
];
// Find first (starting) corner with fallback to 'bottom'
var borders = ['bottom', 'left', 'top', 'right'];
var startCorner = borders.indexOf(borderSkipped, 0);
if (startCorner === -1) {
startCorner = 0;
}
function cornerAt(index) {
return corners[(startCorner + index) % 4];
}
// Draw rectangle from 'startCorner'
var corner = cornerAt(0);
ctx.moveTo(corner[0], corner[1]);
var nextCornerId, nextCorner, width, height, x, y;
for (var i = 1; i < 4; i++) {
corner = cornerAt(i);
nextCornerId = i + 1;
if (nextCornerId == 4) {
nextCornerId = 0
}
nextCorner = cornerAt(nextCornerId);
width = corners[2][0] - corners[1][0];
height = corners[0][1] - corners[1][1];
x = corners[1][0];
y = corners[1][1];
var radius = cornerRadius;
// Fix radius being too large
if (radius > Math.abs(height) / 2) {
radius = Math.floor(Math.abs(height) / 2);
}
if (radius > Math.abs(width) / 2) {
radius = Math.floor(Math.abs(width) / 2);
}
var x_tl, x_tr, y_tl, y_tr, x_bl, x_br, y_bl, y_br;
if (height < 0) {
// Negative values in a standard bar chart
x_tl = x;
x_tr = x + width;
y_tl = y + height;
y_tr = y + height;
x_bl = x;
x_br = x + width;
y_bl = y;
y_br = y;
// Draw
ctx.moveTo(x_bl + radius, y_bl);
ctx.lineTo(x_br - radius, y_br);
// bottom right
ctx.quadraticCurveTo(x_br, y_br, x_br, y_br - radius);
ctx.lineTo(x_tr, y_tr + radius);
// top right
fullCornerRadius ? ctx.quadraticCurveTo(x_tr, y_tr, x_tr - radius, y_tr) : ctx.lineTo(x_tr, y_tr, x_tr - radius, y_tr);
ctx.lineTo(x_tl + radius, y_tl);
// top left
fullCornerRadius ? ctx.quadraticCurveTo(x_tl, y_tl, x_tl, y_tl + radius) : ctx.lineTo(x_tl, y_tl, x_tl, y_tl + radius);
ctx.lineTo(x_bl, y_bl - radius);
// bottom left
ctx.quadraticCurveTo(x_bl, y_bl, x_bl + radius, y_bl);
} else if (width < 0) {
// Negative values in a horizontal bar chart
x_tl = x + width;
x_tr = x;
y_tl = y;
y_tr = y;
x_bl = x + width;
x_br = x;
y_bl = y + height;
y_br = y + height;
// Draw
ctx.moveTo(x_bl + radius, y_bl);
ctx.lineTo(x_br - radius, y_br);
// Bottom right corner
fullCornerRadius ? ctx.quadraticCurveTo(x_br, y_br, x_br, y_br - radius) : ctx.lineTo(x_br, y_br, x_br, y_br - radius);
ctx.lineTo(x_tr, y_tr + radius);
// top right Corner
fullCornerRadius ? ctx.quadraticCurveTo(x_tr, y_tr, x_tr - radius, y_tr) : ctx.lineTo(x_tr, y_tr, x_tr - radius, y_tr);
ctx.lineTo(x_tl + radius, y_tl);
// top left corner
ctx.quadraticCurveTo(x_tl, y_tl, x_tl, y_tl + radius);
ctx.lineTo(x_bl, y_bl - radius);
// bttom left corner
ctx.quadraticCurveTo(x_bl, y_bl, x_bl + radius, y_bl);
} else {
var lastVisible = 0;
for (var findLast = 0, findLastTo = this._chart.data.datasets.length; findLast < findLastTo; findLast++) {
if (!this._chart.getDatasetMeta(findLast).hidden) {
lastVisible = findLast;
}
}
var rounded = this._datasetIndex === lastVisible;
if (rounded) {
//Positive Value
ctx.moveTo(x + radius, y);
ctx.lineTo(x + width - radius, y);
// top right
ctx.quadraticCurveTo(x + width, y, x + width, y + radius);
ctx.lineTo(x + width, y + height - radius);
// bottom right
if (fullCornerRadius || typeOfChart == 'horizontalBar')
ctx.quadraticCurveTo(x + width, y + height, x + width - radius, y + height);
else
ctx.lineTo(x + width, y + height, x + width - radius, y + height);
ctx.lineTo(x + radius, y + height);
// bottom left
if (fullCornerRadius)
ctx.quadraticCurveTo(x, y + height, x, y + height - radius);
else
ctx.lineTo(x, y + height, x, y + height - radius);
ctx.lineTo(x, y + radius);
// top left
if (fullCornerRadius || typeOfChart == 'bar')
ctx.quadraticCurveTo(x, y, x + radius, y);
else
ctx.lineTo(x, y, x + radius, y);
}else {
ctx.moveTo(x, y);
ctx.lineTo(x + width, y);
ctx.lineTo(x + width, y + height);
ctx.lineTo(x, y + height);
ctx.lineTo(x, y);
}
}
}
ctx.fill();
if (borderWidth) {
ctx.stroke();
}
};
/**Chart Data**/
var data = {
labels: ["Red", "Blue", "Yellow", "Green", "Purple", "Orange"],
datasets: [{
label: 'data 0',
data: [12, 19, 3, 5, 2, 3],
backgroundColor: [
'rgba(255, 99, 132, 1)',
'rgba(54, 162, 235, 1)',
'rgba(255, 206, 86, 1)',
'rgba(75, 192, 192, 1)',
'rgba(153, 102, 255, 1)',
'rgba(255, 159, 64, 1)'
],
borderWidth: 0
}, {
label: 'data 1',
data: [20, 24, 10, 15, 12, 13],
backgroundColor: [
'rgba(255, 159, 64, 1)',
'rgba(255, 99, 132, 1)',
'rgba(255, 206, 86, 1)',
'rgba(54, 162, 235, 1)',
'rgba(153, 102, 255, 1)',
'rgba(75, 192, 192, 1)'
],
borderWidth: 0
}, {
label: 'data 2',
data: [20, 30, 30, 20, 14, 20],
backgroundColor: [
'rgba(75, 192, 192, 1)',
'rgba(255, 159, 64, 1)',
'rgba(255, 99, 132, 1)',
'rgba(255, 206, 86, 1)',
'rgba(54, 162, 235, 1)',
'rgba(153, 102, 255, 1)'
],
borderWidth: 0
}]
};
/**Chart Options - Radius options are here**/
var options = {
//Border radius; Default: 0; If a negative value is passed, it will overwrite to 0;
cornerRadius: 10,
//Default: false; if true, this would round all corners of final box;
fullCornerRadius: false,
//Default: false; if true, this rounds each box in the stack instead of only final box;
stackedRounded: false,
elements: {
point: {
radius: 25,
hoverRadius: 35,
pointStyle: 'rectRounded',
}
},
scales: {
yAxes: [{
ticks: {
beginAtZero: true
},
stacked: true,
radius: 25
}],
xAxes: [{
ticks: {
beginAtZero: true
},
stacked: true,
}]
}
};
/**Generate Chart**/
var ctxBar = document.getElementById("myChart");
var myBarChart = new Chart(ctxBar, {
type: 'bar',
data: data,
options: options
});<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.7.1/Chart.js"></script>
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3đź‘Ť
Solution by @jordanwillis doesn’t work with chart.js version after 2.8.0.
To make it work just add following code before drawRoundedTopRectangle definition
Chart.helpers.merge(Chart.defaults.global, {
datasets: {
roundedBar: {
categoryPercentage: 0.8,
barPercentage: 0.9
}
}
});
3đź‘Ť
Got this working in Angular 11 and Charts.js version 2.9.4 (might work in other versions too)
Add this at the very end of your .component.ts file after export class { .. }
Chart['elements'].Rectangle.prototype.draw = function() {
let ctx = this._chart.ctx;
let view = this._view;
//////////////////// edit this to change how rounded the edges are /////////////////////
let borderRadius = 10;
let left = view.x - view.width / 2;
let right = view.x + view.width / 2;
let top = view.y;
let bottom = view.base;
ctx.beginPath();
ctx.fillStyle = view.backgroundColor;
ctx.strokeStyle = view.borderColor;
ctx.lineWidth = view.borderWidth;
let barCorners = [
[left, bottom],
[left, top],
[right, top],
[right, bottom]
];
//start in bottom-left
ctx.moveTo(barCorners[0][0], barCorners[0][1]);
for (let i = 1; i < 4; i++) {
let x = barCorners[1][0];
let y = barCorners[1][1];
let width = barCorners[2][0] - barCorners[1][0];
let height = barCorners[0][1] - barCorners[1][1];
//Fix radius being too big for small values
if(borderRadius > width/2){
borderRadius = width/2;
}
if(borderRadius > height/2){
borderRadius = height/2;
}
// DRAW THE LINES THAT WILL BE FILLED - REPLACING lineTo with quadraticCurveTo CAUSES MORE EDGES TO BECOME ROUNDED
ctx.moveTo(x + borderRadius, y);
ctx.lineTo(x + width - borderRadius, y);
ctx.quadraticCurveTo(x + width, y, x + width, y + borderRadius);
ctx.lineTo(x + width, y + height - borderRadius);
ctx.lineTo(x + width, y + height, x + width - borderRadius, y + height);
ctx.lineTo(x + borderRadius, y + height);
ctx.lineTo(x, y + height, x, y + height - borderRadius);
ctx.lineTo(x, y + borderRadius);
ctx.quadraticCurveTo(x, y, x + borderRadius, y);
}
//FILL THE LINES
ctx.fill();
};
example ngOnInit method:
ngOnInit() {
console.log("asdf entering getChart");
this.canvas = document.getElementById('NumberOfSessionsChart');
this.ctx = this.canvas.getContext('2d');
this.myChart = new Chart(this.ctx, {
type: 'bar',
data: {
labels: ['Jan 20', 'Feb 20', 'Mar 20', 'Apr 20', 'May 20', 'Jun 20', 'Jul 20', 'Aug 20', 'Sept 20'],
datasets: [{
label: 'vVals',
backgroundColor: 'blue',
data: [0, 50, 20, 30, 40, 50, 60, 70, 80, 90, 100],
}]
},
options: {
devicePixelRatio: 2.2,
//tooltips are the things that appear when you hover over the data that show the counts.
//for some reason we can't choose where the tooltip is oriented.
tooltips: {
enabled: false
},
onClick: (e) => {
console.log("asdf entering on click");
},
legend: {
display: true,
position: 'right',
reverse: true,
labels: {
fontColor: 'black',
fontSize: 15,
padding: 20,
usePointStyle: true,
//width of circles in legend
boxWidth: 9
}
},
scales: {
xAxes: [{
ticks: {
padding: 10,
fontSize: 13,
fontFamily: 'Roboto',
fontColor: 'black',
beginAtZero: true
},
gridLines: {
tickMarkLength: 0,
color: '#9da0a2',
drawOnChartArea: false,
},
}],
yAxes: [{
ticks: {
padding: 10,
fontSize: 13,
fontFamily: 'Roboto',
fontColor: 'black',
beginAtZero: true,
precision:0
},
gridLines: {
tickMarkLength: 0,
color: '#9da0a2',
drawOnChartArea: false,
},
}],
},
responsive: false,
}
});
}
}
2đź‘Ť
Also worth a mention is this solution which takes you 30 seconds to implement:
https://github.com/jedtrow/Chart.js-Rounded-Bar-Charts
Download and put the .js file into your projects folder, load it and use
var options = {
cornerRadius: 20,
};
to get rounded bars.
Credits: https://github.com/jedtrow
0đź‘Ť
Checkout chartjs-top-round-bar a usefull
You just need to
import 'chartjs-top-round-bar';
…
new Chart('myChart',
{
options: {
barRoundness: 0.3
}
}
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Source:stackexchange.com