How to add rectangle/arrow to my canvas line? - javascript

I have this code to show wind direction on html canvas:
var x, y, r, ctx, radians;
ctx = window.compass.getContext("2d");
radians = 0.0174533 * (10 - 90);
x = ctx.canvas.width / 2;
y = ctx.canvas.height / 2;
r = x * 0.8;
ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height );
ctx.beginPath();
ctx.strokeStyle = "red"
ctx.fillStyle = "rgba(255,0,0,0.5)";
ctx.lineCap = 'square';
ctx.shadowOffsetX = 4;
ctx.shadowOffsetY = 4;
ctx.shadowBlur = 2;
ctx.shadowColor = "rgba(0, 0, 0, 0.5)";
ctx.lineWidth = 10;
ctx.moveTo(x, y);
ctx.lineTo(x + r * Math.cos(radians), y + r * Math.sin(radians));
ctx.stroke();
I want to add arrowhead to the start point of the line, i.e
x = ctx.canvas.width / 2;
y = ctx.canvas.height / 2;
how can I do this?


Creating a reusable wind-arrow is fairly straightforward:
Create your shadowed arrow on an in-memory canvas:
var memCanvas=document.createElement('canvas')
Draw the in-memory canvas onto the visible canvas:
ctx.drawImage(memCanvas,x,y);
Here's example code and a Demo:
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
var cw=canvas.width;
var ch=canvas.height;
var cx=150;
var cy=150;
var angle=0;
var arrow=makeArrow(100,10,20,20,'red',4);
requestAnimationFrame(animate);
function animate(time){
ctx.clearRect(0,0,cw,ch);
drawArrow(cx,cy,angle);
angle+=Math.PI/180;
requestAnimationFrame(animate);
}
function drawArrow(cx,cy,radianAngle){
ctx.translate(cx,cy);
ctx.rotate(radianAngle);
ctx.drawImage(arrow,-arrow.width/2,-arrow.height/2);
ctx.rotate(-radianAngle);
ctx.translate(-cx,-cy);
}
function makeArrow(length,lineHeight,arrowLength,arrowHeight,fillcolor,shadowoffset){
var lineTop=(arrowHeight-lineHeight)/2;
var arrowLeft=length-arrowLength;
var c=document.createElement('canvas');
var ctx=c.getContext('2d');
c.width=length+shadowoffset;
c.height=arrowHeight+shadowoffset;
ctx.shadowOffsetX = shadowoffset;
ctx.shadowOffsetY = shadowoffset;
ctx.shadowBlur = 2;
ctx.shadowColor = "rgba(0, 0, 0, 0.5)";
ctx.beginPath();
ctx.moveTo(0,lineTop);
ctx.lineTo(arrowLeft,lineTop);
ctx.lineTo(arrowLeft,0);
ctx.lineTo(length,arrowHeight/2);
ctx.lineTo(arrowLeft,arrowHeight);
ctx.lineTo(arrowLeft,lineTop+lineHeight);
ctx.lineTo(0,lineTop+lineHeight);
ctx.closePath();
ctx.fillStyle=fillcolor;
ctx.fill();
return(c);
}
body{ background-color:white; padding:10px; }
canvas{border:1px solid red; margin:0 auto; }
<canvas id="canvas" width=300 height=300></canvas>

Related

Creating circular time range selection using HTML5 canvas?

For one of my application i am creating circular time range selector widget.I have created the clock dial using html canvas.I need help to select time range by touch and drag on the dial as shown in the imageCircular clock dial. When clicked on the "Add" button, the previous selection should be cleared. Next time i should be able to set new range. this continues. The range value should be stored in a variable. It should work on the mobile device. Your help would be appreciated. http://codepen.io/harish_s/pen/ggpoBq
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var radius = canvas.height / 2;
ctx.translate(radius, radius);
radius = 180;
drawClock();
function drawClock() {
drawFace(ctx, radius);
drawNumbers(ctx, radius);
}
function drawFace(ctx, radius) {
var grad;
ctx.beginPath();
ctx.strokeStyle = "rgb(207,207,207)";
ctx.arc(0, 0, radius, 0, 2*Math.PI);
ctx.lineWidth = 60;
ctx.stroke();
ctx.beginPath();
ctx.arc(0, 0, 150, 0, 2*Math.PI);
ctx.fillStyle = "rgb(243,244,244)";
ctx.fill();
ctx.beginPath();
ctx.arc(0, 0, 50, 0, 2*Math.PI);
ctx.fillStyle = '#333';
ctx.fill();
ctx.font = '25pt Calibri';
ctx.fillStyle = 'white';
ctx.fillText('SET', -25, 10);
}
function drawNumbers(ctx, radius) {
var ang;
var num;
ctx.font = radius*0.20 + "px arial";
ctx.fillStyle = '#000';
ctx.textBaseline="middle";
ctx.textAlign="center";
for(num = 1; num < 13; num++){
ang = num * Math.PI / 6;
ctx.rotate(ang);
ctx.translate(0, -radius*1);
ctx.rotate(-ang);
ctx.fillText(num.toString(), 0, 0);
ctx.rotate(ang);
ctx.translate(0, radius*1);
ctx.rotate(-ang);
}
}
#canvas{
position: absolute;
width: 50%;
left: 35%;
top:5%;
}
<canvas id="canvas" width="1000" height="500">
</canvas>

How can I stop filling my circle at some point?

How can I stop filling my circle at some point?
Like only fill 50% of the circle or 25% of the circle and leave the left over. Just like progress bar.
below is the code Im using but it is filling entire circle.
Kindly please give me suggestions.
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var cw = canvas.width;
var ch = canvas.height;
ctx.lineCap = "round";
var y = ch - 10;
var drawingColor = "#0092f9";
animate();
function animate() {
if (y > 0) {
requestAnimationFrame(animate);
}
ctx.clearRect(0, 0, cw, ch);
ctx.save();
drawContainer(0, null, null);
drawContainer(15, drawingColor, null);
drawContainer(7, "white", "white");
ctx.save();
ctx.clip();
drawLiquid();
ctx.restore();
ctx.restore();
y--;
}
function drawLiquid() {
ctx.beginPath();
ctx.moveTo(0, y);
for (var x = 0; x < 300; x += 1) {
ctx.quadraticCurveTo(x + 5, y+5, x + 5, y);
}
ctx.lineTo(cw, ch);
ctx.lineTo(0, ch);
ctx.closePath();
ctx.fillStyle = drawingColor;
ctx.fill();
}
function drawContainer(linewidth, strokestyle, fillstyle) {
ctx.beginPath();
ctx.arc(cw/2, ch/2,cw/2-30,0,2*Math.PI);
ctx.lineWidth = linewidth;
ctx.strokeStyle = strokestyle;
ctx.stroke();
if (fillstyle) {
ctx.fillStyle = fillstyle;
ctx.fill();
}
}
<canvas id="canvas" width=200 height=200></canvas>

I know zit at javascript but: Just change the limit of y in animate. I put 100 instead of 0 and it fills half the circle.
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var cw = canvas.width;
var ch = canvas.height;
ctx.lineCap = "round";
var y = ch - 10;
var drawingColor = "#0092f9";
animate();
function animate() {
if (y > 100) {
requestAnimationFrame(animate);
}
ctx.clearRect(0, 0, cw, ch);
ctx.save();
drawContainer(0, null, null);
drawContainer(15, drawingColor, null);
drawContainer(7, "white", "white");
ctx.save();
ctx.clip();
drawLiquid();
ctx.restore();
ctx.restore();
y--;
}
function drawLiquid() {
ctx.beginPath();
ctx.moveTo(0, y);
for (var x = 0; x < 300; x += 1) {
ctx.quadraticCurveTo(x + 5, y+5, x + 5, y);
}
ctx.lineTo(cw, ch);
ctx.lineTo(0, ch);
ctx.closePath();
ctx.fillStyle = drawingColor;
ctx.fill();
}
function drawContainer(linewidth, strokestyle, fillstyle) {
ctx.beginPath();
ctx.arc(cw/2, ch/2,cw/2-30,0,2*Math.PI);
ctx.lineWidth = linewidth;
ctx.strokeStyle = strokestyle;
ctx.stroke();
if (fillstyle) {
ctx.fillStyle = fillstyle;
ctx.fill();
}
}
<canvas id="canvas" width=200 height=200></canvas>

Drawing a slime from Dragon Quest

Basically I want to draw a slime from Dragon Quest (it looks like a water drop). I have done the following, but I'd like to know if there is a better way to do it. Maybe using Bezier curves or something like that?
Update:
I actually got everything to look like how I want it, except for the gradient for the glow spots (white)
Slime.prototype.drawEye = function(x,y,w,h)
{
ctx.save();
ctx.lineWidth = 3;
ctx.beginPath();
var c = [];
c.push("sclera");
//c.push("iris");
c.push("pupil");
var wScale = [1,2.2,3];
var hScale = [1,2,1.3];
for (var i = 0; i < c.length; i++)
{
w /= wScale[i];
h /= hScale[i];
ctx.beginPath();
ctx.ellipse(x,y,w,h,0,degreesToRadians(360),false);
ctx.fillStyle = this.colors[c[i]];
ctx.fill();
ctx.stroke();
}
ctx.restore();
}
Slime.prototype.drawMouth = function()
{
ctx.save();
ctx.beginPath();
var x = this.x+this.w/30;
var y = this.y+this.h/8;
var w = this.w;
var h = this.h/8;
var start = [x-w/3,y];
var end = [x+w/8,y+h/5];
// mouth
bezierCurve(start,[x-w/3.3,y+h*2.3],[x+w/8,y+h*1.8],end);
bezierCurveTo([x-w/10,y+h*0.6],[x-w/6,y+h*0.6],start);
ctx.lineCap = "round";
ctx.lineWidth = 8;
ctx.stroke();
ctx.clip();
ctx.fillStyle = this.colors["mouth"];
ctx.fill();
start = [x-w/3.5,y+h*1];
// tongue
ctx.beginPath();
bezierCurve(start,[x-w/5,y+h*2.5],[x+w/6.5,y+h*1.6],[x+w/9,y+h*0.75]);
bezierCurveTo([x+w/10,y+h/4],[x-w/5,y],start);
ctx.fillStyle = this.colors["tongue"];
ctx.fill();
//ctx.stroke();
ctx.restore();
}
Slime.prototype.drawHealthBar = function()
{
ctx.beginPath();
ctx.rect(this.x-this.w,this.y+this.h/2+30,this.w*2*this.health/this.maxHealth,20);
ctx.fillStyle = "#00ff00";
ctx.fill();
ctx.beginPath();
ctx.rect(this.x-this.w+(this.w*2*this.health/this.maxHealth),this.y+this.h/2+30,(this.maxHealth-this.health)/this.maxHealth*this.w*2,20);
ctx.fillStyle = "#ff0000";
ctx.fill();
ctx.beginPath();
ctx.rect(this.x-this.w,this.y+this.h/2+30,this.w*2,20);
ctx.strokeStyle = "#000000";
ctx.stroke();
}
Slime.prototype.drawBody = function()
{
ctx.save();
ctx.fillStyle = this.colors["body"];
ctx.beginPath();
var x = this.x;
var y = this.y+this.h*0.4;
var w = this.w/2;
var h = this.h;
var left = [x-w*0.97,this.y+h/11];
var bottom = [x,this.y+h*0.495];
var right = [x+w*0.97,this.y+h/15];
var top = [x+this.w/30,this.y-h/2+this.topOffset];
bezierCurve(left,[x-w,y+h/10],[x-w/7,y+h/12],bottom);
bezierCurveTo([x+w*0.8,y+h/10],[x+w*1.05,y-h/7],right);
y = this.y - (y - this.y);
bezierCurveTo([x+w*0.75,y+h/15],[x+w*0.2,y+h/4.5],top);
bezierCurveTo([x-w*0.2,y+h/5],[x-w*0.8,y+h/10],left);
ctx.lineWidth = 3;
ctx.fill();
ctx.strokeStyle = this.colors["bodyOutline"];
ctx.stroke();
ctx.clip();
ctx.shadowColor = "#000033";
ctx.shadowBlur = 40;
ctx.shadowOffsetX = ctx.shadowBlur/4;
ctx.shadowOffsetY = ctx.shadowOffsetX*-0.8;
ctx.lineWidth = 4;
for (var i = 0; i < 7; i++)
{
if (i%2==0)
{
ctx.shadowColor = "#000033";
}
else
{
ctx.shadowColor = "rgba(0,0,80,0.5)";
}
ctx.stroke();
}
ctx.restore();
}
Slime.prototype.drawGlow = function(x,y,r1,r2)
{
ctx.save();
var g = ctx.createRadialGradient(x,y,r1,x,y,r2);
g.addColorStop(0.0,"#ffffff");
g.addColorStop(1.0,this.colors["body"]);
ctx.beginPath();
ctx.arc(x,y,r2,0,degreesToRadians(360),false);
ctx.fillStyle = g;
ctx.fill();
ctx.restore();
}
Slime.prototype.draw = function()
{
ctx.lineWidth = 2;
this.drawBody();
this.drawMouth();
var w = this.w/10;
var h = this.h/10;
var x = this.x;
var y = this.y;
this.drawEye(x-this.w/4.5,y-h/2.5,w,h);
this.drawEye(this.x+this.w/13,y-h/10,w,h);
this.drawGlow(this.x-this.w/2.5,this.y+this.h/12,this.w/50,this.w/16);
this.drawGlow(this.x+this.w/2*0.7,this.y+this.h/10,this.w/50,this.w/16);
}
End update

Yes, you can draw the droplet outline using just 4 cubic Bezier curves.
Here's a proof-of-concept using just 4 C-Bez curves:
Why! Why! Why! .......... Did I enjoy creating a Slime Man??
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
var cw=canvas.width;
var ch=canvas.height;
drawDropletMan(20,20,'rgb(63,187,255)');
drawDropletMan(255,55,'rgb(255,180,155)');
function drawDropletMan(x,y,fill){
ctx.translate(x,y);
drawBody(fill);
circularGlow(158,111,3,18,fill);
circularGlow(32,107,3,18,fill);
eye(65,87,17,10);
eye(120,90,17,10);
mouth(33,130);
ctx.translate(-x,-y);
}
//
function drawBody(fillcolor){
ctx.save();
ctx.beginPath();
ctx.moveTo(109,0);
ctx.bezierCurveTo(111,64,199,35,198,123);
ctx.bezierCurveTo(199,139,183,192,99,190);
ctx.bezierCurveTo(66,193,-4,167,1,110);
ctx.bezierCurveTo(9,47,97,45,109,1);
ctx.fillStyle=fillcolor;
ctx.fill();
ctx.strokeStyle='black';
ctx.lineWidth=2;
ctx.stroke();
ctx.clip();
ctx.shadowColor='black';
ctx.shadowBlur=15;
ctx.lineWidth=1;
for(var i=0;i<8;i++){ctx.stroke();}
ctx.restore();
}
//
function circularGlow(x,y,r1,r2,fillcolor){
var g=ctx.createRadialGradient(x,y,r1,x,y,r2);
g.addColorStop(0.00,'white');
g.addColorStop(1.00,fillcolor);
ctx.beginPath();
ctx.arc(x,y,r2,0,Math.PI*2);
ctx.fillStyle=g;
ctx.fill();
}
//
function eye(x,y,r1,r2){
ctx.beginPath();
ctx.arc(x,y,r1,0,Math.PI*2);
ctx.fillStyle='white';
ctx.strokeStyle='black';
ctx.fill();
ctx.lineWidth=2;
ctx.stroke();
//
ctx.beginPath();
ctx.arc(x,y,r2,0,Math.PI*2);
ctx.fillStyle='black';
ctx.fill();
}
//
function mouth(){
ctx.save();
ctx.translate(5,5);
ctx.beginPath();
ctx.moveTo(44,120);
ctx.bezierCurveTo(56,136,112,132,128,123);
ctx.bezierCurveTo(138,123,143,123,132,138);
ctx.bezierCurveTo(113,165,49,169,39,127);
ctx.bezierCurveTo(41,128,32,122,44,120);
ctx.closePath();
ctx.fillStyle='black';
ctx.fill();
ctx.clip();
ctx.beginPath();
ctx.arc(90,200,56,0,Math.PI*2);
ctx.fillStyle='coral';
ctx.fill();
ctx.restore();
}
body{ background-color: ivory; }
#canvas{border:1px solid red; margin:0 auto; }
<canvas id="canvas" width=500 height=300></canvas>

Drawing Shadow of an object in Canvas

I want to draw one circle and a character with shadow on a canvas in a HTML page while loading the page and recreate the image on a button click. I am using this code:
window.onload = function() {
draw();
};
function draw(){
var c = document.getElementById("canvas");
var ctx = c.getContext("2d");
ctx.clearRect(0, 0, c.width, c.height);
var width = c.width;
var height = c.height;
//DRAW A CIRCLE
var centerX = Math.floor((Math.random() * width));
var centerY = Math.floor((Math.random() * height));
var radius = Math.floor(Math.random() * 50);
var color = '#f11';
ctx.fillStyle = color;
ctx.beginPath();
ctx.arc(centerX, centerY, radius, 0, Math.PI * 2, false);
ctx.closePath();
ctx.fill();
//DRAW A CHARACTER WITH SHADOW
var c = "S";
ctx.font = "300% Verdana";
ctx.shadowBlur = 20;
ctx.shadowColor = "black";
ctx.shadowOffsetX = 20;
ctx.shadowOffsetY = 20;
ctx.fillStyle = "#111";
ctx.fillText(c, 10, 90);
}
In HTML I am calling draw function onclick() event of a button named Refresh.
For the first time it is giving desired output by drawing one circle and a character with shadow. As I click on the Refresh button it is drawing both the objects with shadow. I dont want to draw shadow of the circle. Can anyone please tell me the mistake I'm doing here.

You may want to use the CanvasRenderingContext2D.save() method :
window.onload = function() {
draw();
};
document.getElementById("canvas").addEventListener('click', draw);
function draw(){
var c = document.getElementById("canvas");
var ctx = c.getContext("2d");
ctx.clearRect(0, 0, c.width, c.height);
var width = c.width;
var height = c.height;
//DRAW A CIRCLE
var centerX = Math.floor((Math.random() * width));
var centerY = Math.floor((Math.random() * height));
var radius = Math.floor(Math.random() * 50);
var color = '#f11';
ctx.fillStyle = color;
ctx.beginPath();
ctx.arc(centerX, centerY, radius, 0, Math.PI * 2, false);
ctx.closePath();
ctx.fill();
//DRAW A CHARACTER WITH SHADOW
//save the actual context
ctx.save();
var c = "S";
ctx.font = "300% Verdana";
ctx.shadowBlur = 20;
ctx.shadowColor = "black";
ctx.shadowOffsetX = 20;
ctx.shadowOffsetY = 20;
ctx.fillStyle = "#111";
ctx.fillText(c, 10, 90);
//restore it
ctx.restore();
}
canvas{border:1px solid;}
<canvas id="canvas" width="400" height="200"></canvas>

how to make an object turn around a point in html5 canvas

The problem is demonstrated in the image below
In other words, how to exactly compute the x and y coordinates for every frame?
ctx.arc(x,y,radius,0,pi*2,false)
because after incrementing one coordinate, I have a problem how to compute the other
I tried this but doesn't work
var step=2,x=100,y=100,r=50,coordinates=[[x,y-r]];
for(var i=1;i <r;i+=step){
bx=x;
x+=step;
y=y-Math.sqrt(Math.pow(r,2)-Math.pow(bx-x,2))
coordinates[i]=[x,y];
}
a jsfiddle will be appreciated.

var canvas = document.querySelector("#c");
var ctx = canvas.getContext("2d");
var centerX = canvas.width / 2;
var centerY = canvas.height / 2;
var speed = 10; // Lower is faster
function animate(t){
ctx.save();
ctx.clearRect (0 , 0 ,canvas.width ,canvas.height );
ctx.translate(canvas.width/2, canvas.height/2);
// First circle
ctx.beginPath();
ctx.arc(0, 0, 5, 0, 2 * Math.PI, false);
ctx.fillStyle = 'blue';
ctx.fill();
ctx.closePath();
// rotate + move along
ctx.rotate((t/speed)/100);
ctx.translate(100,0);
// Orbiting cirle
ctx.beginPath();
ctx.arc(0, 0, 10, 0, 2 * Math.PI, false);
ctx.fillStyle = 'red';
ctx.fill();
ctx.closePath();
ctx.restore();
requestAnimationFrame(animate);
}
requestAnimationFrame(animate);
canvas {
border: 1px solid black;
}
<canvas id="c" width="512" height="512"></canvas>

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