Develop Reference

SVG: how to draw multiple semicircles (arcs) path

Using the answer from this thread I was able to draw a semicircle (arc):
function polarToCartesian(centerX, centerY, radius, angleInDegrees) {
var angleInRadians = (angleInDegrees - 90) * Math.PI / 180.0;
return {
x: centerX + (radius * Math.cos(angleInRadians)),
y: centerY + (radius * Math.sin(angleInRadians))
};
}
function describeArc(x, y, radius, startAngle, endAngle) {
var start = polarToCartesian(x, y, radius, endAngle);
var end = polarToCartesian(x, y, radius, startAngle);
var largeArcFlag = endAngle - startAngle <= 180 ? "0" : "1";
var d = [
"M", start.x, start.y,
"A", radius, radius, 0, largeArcFlag, 0, end.x, end.y
].join(" ");
console.log(d)
return d;
}
window.onload = function() {
document.getElementById("arc1").setAttribute("d", describeArc(100, 100, 50, -90, 90));
};
<svg width="1000" height="1000">
<path id="arc1" fill="red" stroke="#446688" stroke-width="2" />
</svg>
What I'm trying to achieve is to be able to draw an SVG as a path consistent with many arcs (semicircles) and be able to set fill on them.
Something like this:
<svg xmlns="http://www.w3.org/2000/svg">
<path d="M 50 100 A 10 10 0 0 1 100 100 M 100 100 A 10 10 0 0 1 150 100 M 150 100 A 10 10 0 0 1 200 100 M 200 100 A 10 10 0 0 1 250 100" fill="red" stroke="blue" stroke-width="3" />
</svg>
Is there a better way to achieve a simpler path? For now, it looks like this:
<svg xmlns="http://www.w3.org/2000/svg">
<path d="M 50 100 A 10 10 0 0 1 100 100 M 100 100 A 10 10 0 0 1 150 100 M 150 100 A 10 10 0 0 1 200 100 M 200 100 A 10 10 0 0 1 250 100" fill="red" stroke="blue" stroke-width="3" />
</svg>
Or do I have to generate a longer and longer path when there are, let's say, 30 semicircles?
Edit: the IE9+ support is required. Also, those elements will be clickable, draggable and controllable. By controllable I mean that their number and size will change when mouse clicking/moving.
I choose my first approach with a dynamic very long path.
Thanks!

For this I would use lower case commands. For example this is drawing the arc you need: an arc with a radius of 25 and an ending point 50 units ( 2 * 25 ) away from the starting point of the arc.
<svg xmlns="http://www.w3.org/2000/svg">
<path d="M 50 100 a 25 25 0 0 1 50 0" fill="red" stroke="blue" stroke-width="3" />
</svg>
In order to get a path of 4 arcs you need to repeat the arc (a 25 25 0 0 1 50 0) 4 times something like this:
<svg xmlns="http://www.w3.org/2000/svg">
<path d="M 50 100 a 25 25 0 0 1 50 0
a 25 25 0 0 1 50 0
a 25 25 0 0 1 50 0
a 25 25 0 0 1 50 0 " fill="red" stroke="blue" stroke-width="3" />
</svg>
It's easy to see how you can use javascript to generate the d attribute you need:
let d ="M 50 100";
for(let i=0; i<4;i++){d +="a 25 25 0 0 1 50 0 "}
document.querySelector("path").setAttribute("d",d);
<svg xmlns="http://www.w3.org/2000/svg">
<path d="M 50 100" fill="red" stroke="blue" stroke-width="3" />
</svg>

You can use a vanilla JavaScript Web Component (supported in all modern Browsers) to create the SVG
Your Custom Element <svg-arcs repeat="7"></svg-arcs> then creates:
<style>
svg { background: pink }
svg path { stroke-width: 3 }
</style>
<svg-arcs repeat="30"></svg-arcs>
<script>
customElements.define("svg-arcs", class extends HTMLElement {
connectedCallback() {
let repeat = this.getAttribute("repeat") || 5;
let svg = document.createElementNS("http://www.w3.org/2000/svg", "svg");
for (let x = 0; x < repeat; x++) {
let path = document.createElementNS("http://www.w3.org/2000/svg", "path");
path.setAttribute("d", `M${3 + 50*x} 100 A 10 10 0 0 1 ${50+50*x} 100`);
path.setAttribute("fill", "red");
path.setAttribute("stroke", "blue");
svg.append(path);
}
svg.setAttribute("viewBox", `0 0 ${50*repeat + 3} 150`);
this.append(svg);
}
})
</script>
For more dynamic control over individual arcs see the Web Component in SO post:
Firefox: shadow-DOM compatibility

You could use a pattern and size your patterned object appropriately. Here is one that accomodates 4 iterations.
Edit & Update:
If you want those arcs to be independently clickable/draggable, then they need to be separately addressable in the DOM. The "use" element might be what you're looking for.
svg {
background: grey;
}
<svg width="800px" height="600px">
<defs>
<path id="arc-template" d="M1.5 50 a 10 10 0 0 1 97 0" fill="red" stroke="blue" stroke-width="3" />
</defs>
<use id="arc1" href="#arc-template" x="50" y="100"/>
<use id="arc2" href="#arc-template" x="150" y="100"/>
<use id="arc3" href="#arc-template" x="250" y="100"/>
<use id="arc4" href="#arc-template" x="350" y="100"/>
</svg>

SVG arc slider for range input

My goal is to design an arc slider which looks something like that
I have the following structure of the template
<svg width="500" height="300">
<path id="track" stroke="lightgrey" fill="transparent" stroke-width="20" d="
M 50 50
A 90 90 0 0 0 300 50
"/>
<path id="trackFill" fill="cyan" stroke-width="20" d="
M 50 50
A 90 90 0 0 0 [some dynamic value?] [some dynamic value?]
"/>
<circle id="knob" fill="lightblue" cx="[dynamic, initial - 50]" cy="[dynamic, initial - 50]" r="25"/>
</svg>
knob - the control which user is supposed to drag in order to change the value
track - the full arc of the slide
trackFill - the portion of the slider path before the knob
Is it possible to make trackFill cover the portion of the slider before the knob as it is being dragged along the slider curve? If so which APIs or CSS rules will help me to achieve such a result?

Is it something like this you are after?
let svg = document.getElementById("slider");
let trackFill = document.getElementById("trackFill");
let knob = document.getElementById("knob");
let isDragging = false;
let sliderDragOffset = {dx: 0, dy: 0};
let ARC_CENTRE = {x: 175, y: 50};
let ARC_RADIUS = 125;
let sliderValue = 0;
setSliderValue(sliderValue);
function setSliderValue(value)
{
// Limit value to (0..sliderMax)
let sliderMax = track.getTotalLength();
sliderValue = Math.max(0, Math.min(value, sliderMax));
// Calculate new position of knob
let knobRotation = sliderValue * Math.PI / sliderMax;
let knobX = ARC_CENTRE.x - Math.cos(knobRotation) * ARC_RADIUS;
let knobY = ARC_CENTRE.y + Math.sin(knobRotation) * ARC_RADIUS;
// Adjust trackFill dash patter to only draw the portion up to the knob position
trackFill.setAttribute("stroke-dasharray", sliderValue + " " + sliderMax);
// Update the knob position
knob.setAttribute("cx", knobX);
knob.setAttribute("cy", knobY);
}
knob.addEventListener("mousedown", evt => {
isDragging = true;
// Remember where we clicked on knob in order to allow accurate dragging
sliderDragOffset.dx = evt.offsetX - knob.cx.baseVal.value;
sliderDragOffset.dy = evt.offsetY - knob.cy.baseVal.value;
// Attach move event to svg, so that it works if you move outside knob circle
svg.addEventListener("mousemove", knobMove);
// Attach move event to window, so that it works if you move outside svg
window.addEventListener("mouseup", knobRelease);
});
function knobMove(evt)
{
// Calculate adjusted drag position
let x = evt.offsetX + sliderDragOffset.dx;
let y = evt.offsetY + sliderDragOffset.dy;
// Position relative to centre of slider arc
x -= ARC_CENTRE.x;
y -= ARC_CENTRE.y;
// Get angle of drag position relative to slider centre
let angle = Math.atan2(y, -x);
// Positions above arc centre will be negative, so handle them gracefully
// by clamping angle to the nearest end of the arc
angle = (angle < -Math.PI / 2) ? Math.PI : (angle < 0) ? 0 : angle;
// Calculate new slider value from this angle (sliderMaxLength * angle / 180deg)
setSliderValue(angle * track.getTotalLength() / Math.PI);
}
function knobRelease(evt)
{
// Cancel event handlers
svg.removeEventListener("mousemove", knobMove);
window.removeEventListener("mouseup", knobRelease);
isDragging = false;
}
<svg id="slider" width="500" height="300">
<g stroke="lightgrey">
<path id="track" fill="transparent" stroke-width="20" d="
M 50 50
A 125 125 0 0 0 300 50
"/>
</g>
<use id="trackFill" xlink:href="#track" stroke="cyan"/>
<circle id="knob" fill="lightblue" cx="50" cy="50" r="25"/>
</svg>
I've kept this code simple for clarity, but at the expense of some limitations.
It assumes there is only one slider per page. If you need more than that, you will have to keep the slider-specific values (eg sliderValue and, isDragging) separate. You could use data attributes for that. You would also need to switch from accessing the SVG elements via id attributes to another way (eg. class attributes), because id attributes must be unique on the page.

Here is a simple example:
const radius = 50;
const offsetX = 10;
const offsetY = 10;
// 0 <= pos <= 1
const setSliderPos = (svg, pos) => {
const angle = Math.PI * pos;
const x = offsetX + radius - Math.cos(angle) * radius;
const y = offsetY + Math.sin(angle) * radius;
svg.select('.knob').attr('cx', x).attr('cy', y);
svg.select('.first').attr('d', `M ${offsetX},${offsetY} A ${radius},${radius} 0 0 0 ${x},${y}`);
svg.select('.second').attr('d', `M ${x},${y} A ${radius},${radius} 0 0 0 ${offsetX + radius * 2},${offsetY}`);
}
setSliderPos(d3.select('#svg-1'), 0.3);
setSliderPos(d3.select('#svg-2'), 0.6);
setSliderPos(d3.select('#svg-3'), 1);
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/5.7.0/d3.min.js"></script>
<svg id="svg-1" width="150" height="80">
<path class="first" stroke-width="5" stroke="lightblue" fill="none"/>
<path class="second" stroke-width="5" stroke="cyan" fill="none"/>
<circle class="knob" r="10" fill="lightblue"/>
</svg>
<svg id="svg-2" width="150" height="80">
<path class="first" stroke-width="5" stroke="lightblue" fill="none"/>
<path class="second" stroke-width="5" stroke="cyan" fill="none"/>
<circle class="knob" r="10" fill="lightblue"/>
</svg>
<svg id="svg-3" width="150" height="80">
<path class="first" stroke-width="5" stroke="lightblue" fill="none"/>
<path class="second" stroke-width="5" stroke="cyan" fill="none"/>
<circle class="knob" r="10" fill="lightblue"/>
</svg>

To mark the progress you can use stroke-dasharray with a percentage; for example
<g stroke="lightgrey">
<path id="track" fill="transparent" stroke-width="20"
stroke-dasharray="40% 60%"
d="M 50 50 A 125 125 0 0 0 300 50"/>
</g>
This will show 40% of the arc and hide 60% of the arc.
If you need to use two colors, for example the whole arc in grey and the progress in black, you need to use two arcs on top of one another; the one at the bottom would be the one you already have, and the one at the top would have a stroke in black and use stroke-dasharray as shown.

Draw SVG dashed line on scroll? [closed]

Closed. This question needs debugging details. It is not currently accepting answers.
Edit the question to include desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem. This will help others answer the question.
Closed 4 years ago.
Improve this question
I want to have a svg dashed line drawn on scroll and got stuck on this for 4hrs.
If it's just a straight line, I can easily animate it by setting stroke-dasharray on css animation, but it doesn't work on a dashed line.
Since there's a background image on body, I cannot use a mask trick either.
I just want to have a simple 45 degree diagonal dashed line (about 100px) drawn on scroll.
Any advice?

In the next example I'm using the wheel event but you can use scroll instead. And I'm cheating. I'm drawing a dashed path over the path I want to animate. You'll see the animated path through the gaps. I hope it helps.
var svg = document.querySelector("svg");
var l = track.getTotalLength();
var dasharray = l;
var dashoffset = l;
theUse.style.strokeDasharray = dasharray;
theUse.style.strokeDashoffset = dashoffset;
document.addEventListener("wheel",
function(e) {
e.preventDefault();
if (dashoffset > 0 && e.deltaY > 0 ||
dashoffset < l && e.deltaY < 0) {
dashoffset -= e.deltaY;
}
if(dashoffset < 0)dashoffset = 0;
if(dashoffset > l)dashoffset = l;
theUse.style.strokeDashoffset = dashoffset;
}, false);
svg{border:1px solid}
<svg id="svg" xmlns="http://www.w3.org/2000/svg" viewBox="0 -23 238 120">
<defs>
<path id="track" fill="none" d="M18.265,6.037c0,0,22.354-2.458,32.585,2.709c13.401,6.768,22.928,25.006,33.864,30.677c10.935,5.67,11.901,9.014,21.216,8.608c10.013-0.435,11.08-5.485,14.862-5.485
c9.801,0,25.631,24.662,36.168,24.115c14.971-0.777,9.135-0.936,22.096-0.531c12.959,0.406,29.501,7.144,41.247,4.309"/>
</defs>
<use xlink:href="#track" id="theUse" stroke="black" />
<use xlink:href="#track" stroke-dasharray="10 10" stroke="white" stroke-width="2" />
UPDATE
Someone commented:
what we are supposed to see .. because I see nothing when running the snippet
When moving the wheel of your mouse you should see something like this:
UPDATE 2
I'm updating again as an answer to another comment:
ok I don't have a wheel, but why not considering the scroll as stated in the question
Next comes a demo where I'm using the scroll event:
var l = thePath.getTotalLength();
var dasharray = l;
track.style.strokeDasharray = dasharray;
var dashoffset = l;
track.style.strokeDashoffset = dashoffset;
wrap.addEventListener("scroll", function() {
// - 10 is because I want to offset slightly the dashoffse
dashoffset =
-10 + l - this.scrollTop * l / (this.scrollHeight - this.clientHeight);
track.style.strokeDashoffset = dashoffset;
});
#wrap,svg{border:1px solid}
#wrap{height:200px; overflow:scroll}
use{fill:none}
<div id="wrap">
<svg id="svg"
width="100" viewBox="0 0 78.571 753.021" >
<defs>
<path id="thePath" d="M46.249,7c0,0-37.5,0-37.5,32.812s20.312,56.25,37.5,75
s23.881,51.525,6.25,73.438c-31.43,39.062,21.875,43.882,18.75,70.378s-35.938,63.997-45.312,90.559s17.08,37.5,23.438,81.25
s-23.438,75-18.75,118.75s45.312,75,26.562,103.125s-51.812,83.438-50.125,100"/>
</defs>
<use xlink:href="#thePath" id="track" stroke="black" />
<use xlink:href="#thePath" stroke-dasharray="10 10" stroke="white" stroke-width="2" />
</svg>
</div>
UPDATE num 3
Got another comment:
You should use a mask instead of a white path for hiding the dashed path, so that everything but the dashes remains transparent. Like here: Animate dashed SVG line
Inspired by this answer Animate dashed SVG line I'm using a mask instead of a white path.
var l = thePath.getTotalLength();
var dasharray = l;
mask.style.strokeDasharray = dasharray;
var dashoffset = l;
mask.style.strokeDashoffset = dashoffset;
wrap.addEventListener("scroll", function() {
dashoffset =
l - this.scrollTop * l / (this.scrollHeight - this.clientHeight);
mask.style.strokeDashoffset = dashoffset;
});
#wrap,svg{border:1px solid}
#wrap{height:200px; overflow:scroll}
use{fill:none;}
path{stroke-width:3px;}
#mask{stroke:white}
<div id="wrap">
<svg id="svg"
width="100" viewBox="0 0 78.571 753.021" >
<defs>
<path id="thePath" d="M46.249,7c0,0-37.5,0-37.5,32.812s20.312,56.25,37.5,75
s23.881,51.525,6.25,73.438c-31.43,39.062,21.875,43.882,18.75,70.378s-35.938,63.997-45.312,90.559s17.08,37.5,23.438,81.25
s-23.438,75-18.75,118.75s45.312,75,26.562,103.125s-51.812,83.438-50.125,100"/>
<mask id="mask1">
<use id="mask" xlink:href="#thePath" />
</mask>
</defs>
<use xlink:href="#thePath" stroke-dasharray="10 10" stroke="black" mask="url(#mask1)" />
</svg>
</div>

How to find the midPoint of arc in SVG with javascript

I want to the mid point of arc in svg.. Can any one tell formula to find the midbpoint of arc.,

The answer to that question is not straightforward. That's because in SVG arcs can be an elliptical arc. For example, what would you say is the midpoint on the following arc?
<svg width="200" height="200" viewBox="0 0 100 100">
<path fill="none" stroke="black" stroke-width="2"
d="M 20,75 A 21,50, 45, 1 1, 60,75"/>
</svg>
Anyway, without getting into complicated formulae, the simplest method is probably to take advantage of SVG's pointAtLength() method.
var myarc = document.getElementById("myarc");
// Get the length of the path
var pathLen = myarc.getTotalLength();
// How far along the path to we want the position?
var pathDistance = pathLen * 0.5;
// Get the X,Y position
var midpoint = myarc.getPointAtLength(pathDistance)
// For fun, let's add a dot at that position to mark it.
var svg = myarc.ownerSVGElement;
var circle = document.createElementNS("http://www.w3.org/2000/svg", "circle");
circle.setAttribute("cx", midpoint.x);
circle.setAttribute("cy", midpoint.y);
circle.setAttribute("r", "5");
circle.setAttribute("fill", "red");
svg.appendChild(circle);
<svg width="200" height="200" viewBox="0 0 100 100">
<path id="myarc" fill="none" stroke="black" stroke-width="2"
d="M 20,75 A 21,50, 45, 1 1, 60,75"/>
</svg>

Raphael JS Question

I am following a tutorial from netuts about raphael js and I dont understand one of the examples, could some one possibly explain this to me in plainer english. I know I should learn more about javascript first.
for(var i = 0; i < 5; i+=1) {
var multiplier = i*5;
paper.circle(250 + (2*multiplier), 100 + multiplier, 50 - multiplier); }
Thanks! Very Much

The code will create five circles
for(var i = 0; i < 5; i+=1) { // loop five times => create five circles
var multiplier = i*5; // multiply i to increase the effect in the next lines
paper.circle( 250 + (2*multiplier), // the x coordinate of the new circle
100 + multiplier, // the y coordinate
50 - multiplier); // the radius
}
Results in this SVG element:
<svg xmlns="http://www.w3.org/2000/svg" version="1.1" width="556" height="109">
<desc>Created with Raphaël</desc>
<defs/>
<circle cx="250" cy="100" r="50" fill="none" stroke="#000"/>
<circle cx="260" cy="105" r="45" fill="none" stroke="#000"/>
<circle cx="270" cy="110" r="40" fill="none" stroke="#000"/>
<circle cx="280" cy="115" r="35" fill="none" stroke="#000"/>
<circle cx="290" cy="120" r="30" fill="none" stroke="#000"/>
</svg>

for(var i = 0; i < 5; i+=1) {
Iterate 5 times. Store the number of times iterated so far in the variable i. The "{" begins the loop.
var multiplier = i * 5;
Multiply i by 5 and store in a variable called multiplier.
paper.circle(250 + (2*multiplier), 100 + multiplier, 50 - multiplier);
Draw a circle with an x coordinate at 250 plus twice the multiplier, a y coordinate at 100 plus the multiplier and with a radius of 50 minus the multiplier. (Essentially a fancy way of getting distinct circles.)
}
End the loop.