I have two drawings: one arc and one circle and I want the circle to follow the end of the arc. Basically, i need to fetch the x&y of the endAngle of the arc so I would use it on the circle to follow it.
//Arc
context.beginPath();
var x2 = canvas.width / 2;
var y2 = canvas.height / 2;
var radius2 = 215;
var startAngle2 = 1.5 * Math.PI;
var endAngle2= 2.3 * Math.PI;
var counterClockwise2 = false;
context.arc(x2, y2, radius2, startAngle2, endAngle2, counterClockwise2);
context.lineWidth = 10;
context.strokeStyle = "blue";
context.stroke();
//Circle
context.beginPath();
var x3 = x2+ 130;
var y3 = y2 + 200;
var radius3 = 20;
var startAngle3 = 0 * Math.PI;
var endAngle3 = 2 * Math.PI;
var counterClockwise3 = false;
context.arc(x3, y3, radius3, startAngle3, endAngle3, counterClockwise3);
context.lineWidth = 5;
context.strokeStyle = "yellow";
context.stroke();
If you want to get the x,y coordinates of the end of the arc, you should work with cos for x and sin for y.
Get the end of your arc (x,y) like so:
var x3 = canvas.width / 2 + radius2*Math.cos(endAngle2);
var y3 = canvas.height / 2 + radius2*Math.sin(endAngle2);
It's easier to use ctx.rotate(angle);
The center of the rotation is the origin of the canvas identified by 0,0. In order to choose another one you need to use ctx.translate(x, y); where x,y are the coordinates of the center of the rotation hence
context.translate(x1,y1)
context.rotate(20*Math.PI/180)
Finally, you need to change your coordinates to refer to the new center
context.arc(x2, y2, radius2, startAngle2, endAngle2, counterClockwise2);
...
....
var x3 = x2 + 130;
var y3 = y2 + 200;
becomes
context.arc(0, 0, radius2, startAngle2, endAngle2, counterClockwise2);
....
...
var x3 = 130;
var y3 = 200;
Here's the full code:
var canvas=document.getElementById("clock");
var context = canvas.getContext('2d');
context.beginPath();
var x1 = canvas.width/2;
var y1 = canvas.height/2;
var radius1 = 200;
var startAngle1 = 0 * Math.PI;
var endAngle1 = 2 * Math.PI;
var counterClockwise1 = false;
context.arc(x1, y1, radius1, startAngle1, endAngle1, counterClockwise1);
context.lineWidth = 20;
context.strokeStyle = 'black';
context.stroke();
context.font = "bold 76px Arial";
context.textAlign="center";
context.textBaseline="middle";
context.fillText("25:00", canvas.width/2, canvas.height/2);
context.beginPath();
context.translate(x1,y1)
context.rotate(Math.PI)
var radius2 = 215;
var startAngle2 = 1.5 * Math.PI;
var endAngle2 = 2.3 * Math.PI;
var counterClockwise2 = false;
context.arc(0, 0, radius2, startAngle2, endAngle2, counterClockwise2);
context.lineWidth = 10;
context.strokeStyle = "blue";
context.stroke();
context.beginPath();
var x3 = 130;
var y3 = 200;
var radius3 = 20;
var startAngle3 = 0 * Math.PI;
var endAngle3 = 2 * Math.PI;
var counterClockwise3 = false;
context.arc(x3, y3, radius3, startAngle3, endAngle3, counterClockwise3);
context.lineWidth = 5;
context.strokeStyle = "yellow";
context.stroke();
body {
background-color: #50B3B9;
}
#clock {
background-color: red;
position:relative;
}
#time {
position:absolute;
top:0px;
}
----------
<div class="container">
<canvas id="clock" width="600" height="600">
<div id="time">25:00</div>
</canvas>
</div>
Related
I'm currently working on a small HTML canvas game (zero point of the canvas top-left). I need the coordinates (X,Y) on a circle.
The radius and the center are known.
My variables:
var radius = 50;
var center_x = 200;
var center_y = 200;
var angle = 45;
The formula for a point on a circle, given the angle, is:
x = xcenter + r·cos(𝛼)
y = ycenter + r·sin(𝛼)
...where 𝛼 is the angle in radians.
Since on a web page the Y coordinate is downwards, you would subtract the term in the formula.
Here is a demo, where the angle changes continually:
var radius = 50;
var center_x = 100;
var center_y = 100;
var angle = 50; // Will change in this demo
const canvas = document.querySelector("canvas");
const ctx = canvas.getContext("2d");
const span = document.querySelector("span");
const loop = () => {
angle = (angle + 1) % 360;
// Formula:
var rad = angle * Math.PI / 180;
var x = center_x + radius * Math.cos(rad);
var y = center_y - radius * Math.sin(rad);
// Draw point
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctx.fillStyle = "#ff2626";
ctx.beginPath();
ctx.arc(x, y, 2, 0, Math.PI * 2, true);
ctx.fill();
// Display angle
span.textContent = angle;
// Repeat at next paint cycle
requestAnimationFrame(loop);
};
loop();
<div>Angle: <span></span></div>
<canvas width=500 height=160></canvas>
I have 2 canvasses that visualize values from 2 different labels.
I wrote 2 almost the same javascripts and when I run my application. It skips the first visualitation and only shows the second one. Where is my mistake?
Here is my html code:-
<div><canvas id="canvas" width="300" height="300"></canvas></div>
<asp:Label ID="LblGauge" runat="server"></asp:Label>
<div><canvas id="canvas2" width="300" height="300"></canvas></div>
<asp:Label ID="LblGauge1" runat="server"></asp:Label>
And here are my 2 javascripts. The only difference now is the canvas/canvas2 and the lblgauge and lblgauge1. Even if I change all the variables in the second script it will still only show the second visualition.
<script>
window.onload = function () {
//canvas initialization
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
//dimensions
var W = canvas.width;
var H = canvas.height;
//Variables
var degrees = document.getElementById("LblGauge").textContent;
var new_degrees = 0;
var difference = 0;
var color = "lightgreen";
var bgcolor = "#222";
var text;
var animation_loop, redraw_loop;
function init() {
//Clear the canvas everytime a chart is drawn
ctx.clearRect(0, 0, W, H);
//Background 360 degree arc
ctx.beginPath();
ctx.strokeStyle = bgcolor;
ctx.lineWidth = 30;
ctx.arc(W / 2, H / 2, 100, 0, Math.PI * 2, false);
ctx.stroke();
//Angle in radians = angle in degrees * PI / 180
var radians = degrees * Math.PI / 180;
ctx.beginPath();
ctx.strokeStyle = color;
ctx.lineWidth = 30;
//the arc will start from the topmost end
ctx.arc(W / 2, H / 2, 100, 0 - 90 * Math.PI / 180, radians - 90 * Math.PI / 180, false);
ctx.stroke();
//Lets add the text
ctx.fillStyle = color;
ctx.font = "50px bebas";
text = Math.floor(degrees / 360 * 100) + "%";
text_width = ctx.measureText(text).width;
ctx.fillText(text, W / 2 - text_width / 2, H / 2 + 15);
}
function draw() {
//Cancel any movement animation if a new chart is requested
if (typeof animation_loop != undefined) clearInterval(animation_loop);
////time for each frame is 1sec / difference in degrees
animation_loop = setInterval(animate_to, 1000 / difference);
}
//function to make the chart move to new degrees
function animate_to() {
if (degrees == new_degrees)
if (degrees < new_degrees)
degrees++;
else
degrees--;
init();
}
draw();
}
</script>
<script>
window.onload = function () {
//canvas initialization
var canvas = document.getElementById("canvas2");
var ctx = canvas.getContext("2d");
//dimensions
var W = canvas.width;
var H = canvas.height;
//Variables
var degrees = document.getElementById("LblGauge1").textContent;
var new_degrees = 0;
var difference = 0;
var color = "lightgreen";
var bgcolor = "#222";
var text;
var animation_loop, redraw_loop;
function init() {
//Clear the canvas everytime a chart is drawn
ctx.clearRect(0, 0, W, H);
//Background 360 degree arc
ctx.beginPath();
ctx.strokeStyle = bgcolor;
ctx.lineWidth = 30;
ctx.arc(W / 2, H / 2, 100, 0, Math.PI * 2, false);
ctx.stroke();
//Angle in radians = angle in degrees * PI / 180
var radians = degrees * Math.PI / 180;
ctx.beginPath();
ctx.strokeStyle = color;
ctx.lineWidth = 30;
//the arc will start from the topmost end
ctx.arc(W / 2, H / 2, 100, 0 - 90 * Math.PI / 180, radians - 90 * Math.PI / 180, false);
ctx.stroke();
//Lets add the text
ctx.fillStyle = color;
ctx.font = "50px bebas";
text = Math.floor(degrees / 360 * 100) + "%";
text_width = ctx.measureText(text).width;
ctx.fillText(text, W / 2 - text_width / 2, H / 2 + 15);
}
function draw() {
//Cancel any movement animation if a new chart is requested
if (typeof animation_loop != undefined) clearInterval(animation_loop);
////time for each frame is 1sec / difference in degrees
animation_loop = setInterval(animate_to, 1000 / difference);
}
//function to make the chart move to new degrees
function animate_to() {
if (degrees == new_degrees)
if (degrees < new_degrees)
degrees++;
else
degrees--;
init();
}
draw();
}
</script>
Can somebody tell me how to change my code.
This is what the javascript shows me when it works.
I'm attempting to draw this shape on screen with canvas.
I have referenced this example which draws a circle: http://jsfiddle.net/loktar/uhVj6/4/ ,but cannot figure it out. Any help would be greatly appreciated. I'm new to canvas.
var canvas = document.getElementById('myCanvas');
var context = canvas.getContext('2d');
var x = canvas.width / 2;
var y = canvas.height / 2;
var radius = 75;
var endPercent = 85;
var curPerc = 0;
var counterClockwise = false;
var circ = Math.PI * 2;
var quart = Math.PI / 2;
context.lineWidth = 10;
context.strokeStyle = '#ad2323';
context.shadowOffsetX = 0;
context.shadowOffsetY = 0;
context.shadowBlur = 10;
context.shadowColor = '#656565';
function animate(current) {
context.clearRect(0, 0, canvas.width, canvas.height);
context.beginPath();
context.arc(x, y, radius, -(quart), ((circ) * current) - quart, false);
context.stroke();
curPerc++;
if (curPerc < endPercent) {
requestAnimationFrame(function () {
animate(curPerc / 100)
});
}
}
animate();
I plan on having a bullet point on each angle that would pop up and slightly pause whenever the line gets to that point.
I have three arcs, the first one loads on page-load, the second one loads on mouse-over and the third one on mouse-out. I want the mouse-over-out effect to happen each time rather than just one time (as it is now).
here's the fiddle: http://jsfiddle.net/krish7878/7bX7n/
Here's the JS code:
var currentEndAngle = 0;
var currentStartAngle = 0;
var currentEndAngle2 = 0;
var currentStartAngle2 = 0;
var currentEndAngle3 = -0.5;
var currentStartAngle3 = -0.5;
var something = setInterval(draw, 5);
$("#canvas1").hover(
function(){
var something2 = setInterval(draw2, 5);
},
function(){
var something3 = setInterval(draw3, 5);
}
);
function draw() { /***************/
var can = document.getElementById('canvas1'); // GET LE CANVAS
var canvas = document.getElementById("canvas1");
var context = canvas.getContext("2d");
var x = canvas.width / 2;
var y = canvas.height / 2;
var radius;
var width;
var currentColor = "#00b5ff";
var radius = 100;
var width = 8;
var startAngle = currentStartAngle * Math.PI;
var endAngle = (currentEndAngle) * Math.PI;
if(currentEndAngle < 0.1){
currentEndAngle = currentEndAngle - 0.01;
}
if (currentEndAngle < -0.5){
clearInterval(something);
}
context.beginPath();
context.arc(x, y, radius, startAngle, endAngle, true);
context.lineWidth = width;
// line color
context.strokeStyle = currentColor;
context.stroke();
/************************************************/
}
function draw2() { /***************/
var can = document.getElementById('canvas1'); // GET LE CANVAS
var canvas = document.getElementById("canvas1");
var context = canvas.getContext("2d");
var x = canvas.width / 2;
var y = canvas.height / 2;
var radius;
var width;
var currentColor = "#000";
var radius = 100;
var width = 7;
var startAngle = currentStartAngle2 * Math.PI;
var endAngle = (currentEndAngle2) * Math.PI;
if(currentEndAngle2 < 0.1){
currentEndAngle2 = currentEndAngle2 - 0.01;
}
if (currentEndAngle2 < -0.55){
clearInterval(something2);
}
context.beginPath();
context.arc(x, y, radius, startAngle, endAngle, true);
context.lineWidth = width;
// line color
context.strokeStyle = currentColor;
context.stroke();
/*
context.beginPath();
context.clearRect ( 0 , 0 , 400 , 400 );
context.stroke():
/************************************************/
}
function draw3() { /***************/
var can = document.getElementById('canvas1'); // GET LE CANVAS
var canvas = document.getElementById("canvas1");
var context = canvas.getContext("2d");
var x = canvas.width / 2;
var y = canvas.height / 2;
var radius;
var width;
var currentColor = "#00b5ff";
var radius = 100;
var width = 8;
var startAngle = currentStartAngle3 * Math.PI;
var endAngle = (currentEndAngle3) * Math.PI;
if(currentEndAngle3 < 0){
currentEndAngle3 = currentEndAngle3 + 0.01;
}
if (currentEndAngle3 > 0){
clearInterval(something3);
}
context.beginPath();
context.arc(x, y, radius, startAngle, endAngle, false);
context.lineWidth = width;
// line color
context.strokeStyle = currentColor;
context.stroke();
/************************************************/
}
Code Explanation: there are three functions draw(), draw2(), draw3() - draw is run when the page loads, it draws a blue arc, draw2() is executed when mouse-over happens and draws a black line, draw3 is run when mouse-out happens.
Show I draw them on individual canvases and clear them individually or is there a method to get this done?
Here's one way to do it:
A Demo: http://jsfiddle.net/m1erickson/wMy4G/
Define an arc object
var arc={
cx:canvas.width/2,
cy:canvas.height/2,
radius:100,
startRadians:0,
endRadians:-Math.PI/2,
linewidth:8,
animationPercent:0,
animationRate:10,
animationDirection:0,
};
Draw a portion of the arc based on an animation point
function drawArc(arc,color){
var rStart=arc.startRadians;
var rEnd=arc.endRadians;
if(!arc.animationDirection==0){
if(arc.animationDirection>0){
rEnd=arc.animationPercent/100*(rEnd-rStart);
}else{
rEnd=(100-arc.animationPercent)/100*(rEnd-rStart);
}
}
ctx.clearRect(0,0,canvas.width,canvas.height);
ctx.beginPath();
ctx.arc(arc.cx,arc.cy,arc.radius,rStart,rEnd,true);
ctx.strokeStyle=color;
ctx.stroke();
}
Animate portions of the arc
function animate(time){
if(continueAnimation){RAF=requestAnimationFrame(animate);}
drawArc(arc,"blue");
arc.animationPercent+=arc.animationRate;
if(arc.animationPercent>=100){
continueAnimation=false;
}
}
React to hover events by drawing or undrawing the arc
$("#canvas").hover(
function(){
cancelAnimationFrame(RAF);
arc.animationPercent=0;
arc.animationDirection=1;
continueAnimation=true;
requestAnimationFrame(animate);
},
function(){
cancelAnimationFrame(RAF);
arc.animationPercent=0;
arc.animationDirection=-1;
continueAnimation=true;
requestAnimationFrame(animate);
}
);
I am just learning some details about html5 canvas, and in the progress, I am trying to build a simple color wheel by wedges (build a 1 degree wedge at a time and add it up to 360 degree). However, I am getting some weird marks on the gradient as shown in the following image:
.
Here is the fiddle that produced the colorwheel: http://jsfiddle.net/53JBM/
In particular, this is the JS code:
var canvas = document.getElementById("picker");
var context = canvas.getContext("2d");
var x = canvas.width / 2;
var y = canvas.height / 2;
var radius = 100;
var counterClockwise = false;
for(var angle=0; angle<=360; angle+=1){
var startAngle = (angle-1)*Math.PI/180;
var endAngle = angle * Math.PI/180;
context.beginPath();
context.moveTo(x, y);
context.arc(x, y, radius, startAngle, endAngle, counterClockwise);
context.closePath();
context.fillStyle = 'hsl('+angle+', 100%, 50%)';
context.fill();
}
If anyone can point out what I am doing wrong or if there is a better way to accomplish what I am attempting to do it would be much appreciated :)
Is this enough to you, please check
var startAngle = (angle-2)*Math.PI/180;
Try this it looks great.
Thanks by the way this is exactly what I was trying to make.
var canvas = document.getElementById("picker");
var context = canvas.getContext("2d");
var x = canvas.width / 2;
var y = canvas.height / 2;
var radius = 100;
var counterClockwise = false;
for(var angle=0; angle<=360; angle+=1){
var startAngle = (angle-2)*Math.PI/180;
var endAngle = angle * Math.PI/180;
context.beginPath();
context.moveTo(x, y);
context.arc(x, y, radius, startAngle, endAngle, counterClockwise);
context.closePath();
var gradient = context.createRadialGradient(x, y, 0, x, y, radius);
gradient.addColorStop(0,'hsl('+angle+', 10%, 100%)');
gradient.addColorStop(1,'hsl('+angle+', 100%, 50%)');
context.fillStyle = gradient;
context.fill();
}
<body>
<canvas id="picker"></canvas>
</body>
Similar approach, just for the color
var canvas = document.getElementById("picker");
var context = canvas.getContext("2d");
var x = canvas.width / 2;
var y = canvas.height / 2;
var radius = 50;
var thickness = 0.6;
for(var angle=0; angle<=360; angle+=1){
var startAngle = (angle-2)*Math.PI/180;
var endAngle = angle * Math.PI/180;
context.beginPath();
context.arc(x, y, (1-thickness/2)*radius, startAngle, endAngle, false);
context.lineWidth = thickness*radius;
context.strokeStyle = 'hsl('+angle+', 100%, 50%)';
context.stroke();
}
<body>
<canvas id="picker"></canvas>
</body>
Edit: full project here: https://github.com/dersimn/jquery-colorwheel