Draw on HTML5 Canvas using a mouse
I want to draw on a HTML Canvas using a mouse (for example, draw a signat开发者_JS百科ure, draw a name, ...)
How would I go about implementing this?
Here is a working sample.
<html>
<script type="text/javascript">
var canvas, ctx, flag = false,
prevX = 0,
currX = 0,
prevY = 0,
currY = 0,
dot_flag = false;
var x = "black",
y = 2;
function init() {
canvas = document.getElementById('can');
ctx = canvas.getContext("2d");
w = canvas.width;
h = canvas.height;
canvas.addEventListener("mousemove", function (e) {
findxy('move', e)
}, false);
canvas.addEventListener("mousedown", function (e) {
findxy('down', e)
}, false);
canvas.addEventListener("mouseup", function (e) {
findxy('up', e)
}, false);
canvas.addEventListener("mouseout", function (e) {
findxy('out', e)
}, false);
}
function color(obj) {
switch (obj.id) {
case "green":
x = "green";
break;
case "blue":
x = "blue";
break;
case "red":
x = "red";
break;
case "yellow":
x = "yellow";
break;
case "orange":
x = "orange";
break;
case "black":
x = "black";
break;
case "white":
x = "white";
break;
}
if (x == "white") y = 14;
else y = 2;
}
function draw() {
ctx.beginPath();
ctx.moveTo(prevX, prevY);
ctx.lineTo(currX, currY);
ctx.strokeStyle = x;
ctx.lineWidth = y;
ctx.stroke();
ctx.closePath();
}
function erase() {
var m = confirm("Want to clear");
if (m) {
ctx.clearRect(0, 0, w, h);
document.getElementById("canvasimg").style.display = "none";
}
}
function save() {
document.getElementById("canvasimg").style.border = "2px solid";
var dataURL = canvas.toDataURL();
document.getElementById("canvasimg").src = dataURL;
document.getElementById("canvasimg").style.display = "inline";
}
function findxy(res, e) {
if (res == 'down') {
prevX = currX;
prevY = currY;
currX = e.clientX - canvas.offsetLeft;
currY = e.clientY - canvas.offsetTop;
flag = true;
dot_flag = true;
if (dot_flag) {
ctx.beginPath();
ctx.fillStyle = x;
ctx.fillRect(currX, currY, 2, 2);
ctx.closePath();
dot_flag = false;
}
}
if (res == 'up' || res == "out") {
flag = false;
}
if (res == 'move') {
if (flag) {
prevX = currX;
prevY = currY;
currX = e.clientX - canvas.offsetLeft;
currY = e.clientY - canvas.offsetTop;
draw();
}
}
}
</script>
<body onload="init()">
<canvas id="can" width="400" height="400" style="position:absolute;top:10%;left:10%;border:2px solid;"></canvas>
<div style="position:absolute;top:12%;left:43%;">Choose Color</div>
<div style="position:absolute;top:15%;left:45%;width:10px;height:10px;background:green;" id="green" onclick="color(this)"></div>
<div style="position:absolute;top:15%;left:46%;width:10px;height:10px;background:blue;" id="blue" onclick="color(this)"></div>
<div style="position:absolute;top:15%;left:47%;width:10px;height:10px;background:red;" id="red" onclick="color(this)"></div>
<div style="position:absolute;top:17%;left:45%;width:10px;height:10px;background:yellow;" id="yellow" onclick="color(this)"></div>
<div style="position:absolute;top:17%;left:46%;width:10px;height:10px;background:orange;" id="orange" onclick="color(this)"></div>
<div style="position:absolute;top:17%;left:47%;width:10px;height:10px;background:black;" id="black" onclick="color(this)"></div>
<div style="position:absolute;top:20%;left:43%;">Eraser</div>
<div style="position:absolute;top:22%;left:45%;width:15px;height:15px;background:white;border:2px solid;" id="white" onclick="color(this)"></div>
<img id="canvasimg" style="position:absolute;top:10%;left:52%;" style="display:none;">
<input type="button" value="save" id="btn" size="30" onclick="save()" style="position:absolute;top:55%;left:10%;">
<input type="button" value="clear" id="clr" size="23" onclick="erase()" style="position:absolute;top:55%;left:15%;">
</body>
</html>
I think, other examples here are too complicated. This one is simpler and JS only...
// create canvas element and append it to document body
var canvas = document.createElement('canvas');
document.body.appendChild(canvas);
// some hotfixes... ( ≖_≖)
document.body.style.margin = 0;
canvas.style.position = 'fixed';
// get canvas 2D context and set him correct size
var ctx = canvas.getContext('2d');
resize();
// last known position
var pos = { x: 0, y: 0 };
window.addEventListener('resize', resize);
document.addEventListener('mousemove', draw);
document.addEventListener('mousedown', setPosition);
document.addEventListener('mouseenter', setPosition);
// new position from mouse event
function setPosition(e) {
pos.x = e.clientX;
pos.y = e.clientY;
}
// resize canvas
function resize() {
ctx.canvas.width = window.innerWidth;
ctx.canvas.height = window.innerHeight;
}
function draw(e) {
// mouse left button must be pressed
if (e.buttons !== 1) return;
ctx.beginPath(); // begin
ctx.lineWidth = 5;
ctx.lineCap = 'round';
ctx.strokeStyle = '#c0392b';
ctx.moveTo(pos.x, pos.y); // from
setPosition(e);
ctx.lineTo(pos.x, pos.y); // to
ctx.stroke(); // draw it!
}
Here's the most straightforward way to create a drawing application with canvas:
- Attach a
mousedown
,mousemove
, andmouseup
event listener to the canvas DOM - on
mousedown
, get the mouse coordinates, and use themoveTo()
method to position your drawing cursor and thebeginPath()
method to begin a new drawing path. - on
mousemove
, continuously add a new point to the path withlineTo()
, and color the last segment withstroke()
. - on
mouseup
, set a flag to disable the drawing.
From there, you can add all kinds of other features like giving the user the ability to choose a line thickness, color, brush strokes, and even layers.
I was looking to use this method for signatures as well, i found a sample on http://codetheory.in/.
I've added the below code to a jsfiddle
Html:
<div id="sketch">
<canvas id="paint"></canvas>
</div>
Javascript:
(function() {
var canvas = document.querySelector('#paint');
var ctx = canvas.getContext('2d');
var sketch = document.querySelector('#sketch');
var sketch_style = getComputedStyle(sketch);
canvas.width = parseInt(sketch_style.getPropertyValue('width'));
canvas.height = parseInt(sketch_style.getPropertyValue('height'));
var mouse = {x: 0, y: 0};
var last_mouse = {x: 0, y: 0};
/* Mouse Capturing Work */
canvas.addEventListener('mousemove', function(e) {
last_mouse.x = mouse.x;
last_mouse.y = mouse.y;
mouse.x = e.pageX - this.offsetLeft;
mouse.y = e.pageY - this.offsetTop;
}, false);
/* Drawing on Paint App */
ctx.lineWidth = 5;
ctx.lineJoin = 'round';
ctx.lineCap = 'round';
ctx.strokeStyle = 'blue';
canvas.addEventListener('mousedown', function(e) {
canvas.addEventListener('mousemove', onPaint, false);
}, false);
canvas.addEventListener('mouseup', function() {
canvas.removeEventListener('mousemove', onPaint, false);
}, false);
var onPaint = function() {
ctx.beginPath();
ctx.moveTo(last_mouse.x, last_mouse.y);
ctx.lineTo(mouse.x, mouse.y);
ctx.closePath();
ctx.stroke();
};
}());
Here is my very simple working canvas draw and erase.
https://jsfiddle.net/richardcwc/d2gxjdva/
//Canvas
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
//Variables
var canvasx = $(canvas).offset().left;
var canvasy = $(canvas).offset().top;
var last_mousex = last_mousey = 0;
var mousex = mousey = 0;
var mousedown = false;
var tooltype = 'draw';
//Mousedown
$(canvas).on('mousedown', function(e) {
last_mousex = mousex = parseInt(e.clientX-canvasx);
last_mousey = mousey = parseInt(e.clientY-canvasy);
mousedown = true;
});
//Mouseup
$(canvas).on('mouseup', function(e) {
mousedown = false;
});
//Mousemove
$(canvas).on('mousemove', function(e) {
mousex = parseInt(e.clientX-canvasx);
mousey = parseInt(e.clientY-canvasy);
if(mousedown) {
ctx.beginPath();
if(tooltype=='draw') {
ctx.globalCompositeOperation = 'source-over';
ctx.strokeStyle = 'black';
ctx.lineWidth = 3;
} else {
ctx.globalCompositeOperation = 'destination-out';
ctx.lineWidth = 10;
}
ctx.moveTo(last_mousex,last_mousey);
ctx.lineTo(mousex,mousey);
ctx.lineJoin = ctx.lineCap = 'round';
ctx.stroke();
}
last_mousex = mousex;
last_mousey = mousey;
//Output
$('#output').html('current: '+mousex+', '+mousey+'<br/>last: '+last_mousex+', '+last_mousey+'<br/>mousedown: '+mousedown);
});
//Use draw|erase
use_tool = function(tool) {
tooltype = tool; //update
}
canvas {
cursor: crosshair;
border: 1px solid #000000;
}
<canvas id="canvas" width="800" height="500"></canvas>
<input type="button" value="draw" onclick="use_tool('draw');" />
<input type="button" value="erase" onclick="use_tool('erase');" />
<div id="output"></div>
I had to provide a simple example for this subject so I'll share here:
http://jsfiddle.net/Haelle/v6tfp2e1
class SignTool {
constructor() {
this.initVars()
this.initEvents()
}
initVars() {
this.canvas = $('#canvas')[0]
this.ctx = this.canvas.getContext("2d")
this.isMouseClicked = false
this.isMouseInCanvas = false
this.prevX = 0
this.currX = 0
this.prevY = 0
this.currY = 0
}
initEvents() {
$('#canvas').on("mousemove", (e) => this.onMouseMove(e))
$('#canvas').on("mousedown", (e) => this.onMouseDown(e))
$('#canvas').on("mouseup", () => this.onMouseUp())
$('#canvas').on("mouseout", () => this.onMouseOut())
$('#canvas').on("mouseenter", (e) => this.onMouseEnter(e))
}
onMouseDown(e) {
this.isMouseClicked = true
this.updateCurrentPosition(e)
}
onMouseUp() {
this.isMouseClicked = false
}
onMouseEnter(e) {
this.isMouseInCanvas = true
this.updateCurrentPosition(e)
}
onMouseOut() {
this.isMouseInCanvas = false
}
onMouseMove(e) {
if (this.isMouseClicked && this.isMouseInCanvas) {
this.updateCurrentPosition(e)
this.draw()
}
}
updateCurrentPosition(e) {
this.prevX = this.currX
this.prevY = this.currY
this.currX = e.clientX - this.canvas.offsetLeft
this.currY = e.clientY - this.canvas.offsetTop
}
draw() {
this.ctx.beginPath()
this.ctx.moveTo(this.prevX, this.prevY)
this.ctx.lineTo(this.currX, this.currY)
this.ctx.strokeStyle = "black"
this.ctx.lineWidth = 2
this.ctx.stroke()
this.ctx.closePath()
}
}
var canvas = new SignTool()
canvas {
position: absolute;
border: 2px solid;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<canvas id="canvas" width="500" height="300"></canvas>
A super short version, here, without position:absolute
in vanilla JavaScript. The main idea is to move the canvas' context to the right coordinates and draw a line. Uncomment click
handler and comment mousedown
& mousemove
handlers below to get a feel for how it is working.
<!DOCTYPE html>
<html>
<body>
<p style="margin: 50px">Just some padding in y direction</p>
<canvas id="myCanvas" width="300" height="300" style="background: #000; margin-left: 100px;">Your browser does not support the HTML5 canvas tag.</canvas>
<script>
const c = document.getElementById("myCanvas");
// c.addEventListener("click", penTool); // fires after mouse left btn is released
c.addEventListener("mousedown", setLastCoords); // fires before mouse left btn is released
c.addEventListener("mousemove", freeForm);
const ctx = c.getContext("2d");
function setLastCoords(e) {
const {x, y} = c.getBoundingClientRect();
lastX = e.clientX - x;
lastY = e.clientY - y;
}
function freeForm(e) {
if (e.buttons !== 1) return; // left button is not pushed yet
penTool(e);
}
function penTool(e) {
const {x, y} = c.getBoundingClientRect();
const newX = e.clientX - x;
const newY = e.clientY - y;
ctx.beginPath();
ctx.lineWidth = 5;
ctx.moveTo(lastX, lastY);
ctx.lineTo(newX, newY);
ctx.strokeStyle = 'white';
ctx.stroke();
ctx.closePath();
lastX = newX;
lastY = newY;
}
let lastX = 0;
let lastY = 0;
</script>
</body>
</html>
It's been years since the question was asked and was answered.
For anyone who looks for a simple drawing canvas (eg, for taking the signature from the user/customer), here I am posting a more simplified jquery version of the currently accepted answer
$(document).ready(function() {
var flag, dot_flag = false,
prevX, prevY, currX, currY = 0,
color = 'black', thickness = 2;
var $canvas = $('#canvas');
var ctx = $canvas[0].getContext('2d');
$canvas.on('mousemove mousedown mouseup mouseout', function(e) {
prevX = currX;
prevY = currY;
currX = e.clientX - $canvas.offset().left;
currY = e.clientY - $canvas.offset().top;
if (e.type == 'mousedown') {
flag = true;
}
if (e.type == 'mouseup' || e.type == 'mouseout') {
flag = false;
}
if (e.type == 'mousemove') {
if (flag) {
ctx.beginPath();
ctx.moveTo(prevX, prevY);
ctx.lineTo(currX, currY);
ctx.strokeStyle = color;
ctx.lineWidth = thickness;
ctx.stroke();
ctx.closePath();
}
}
});
$('.canvas-clear').on('click', function(e) {
c_width = $canvas.width();
c_height = $canvas.height();
ctx.clearRect(0, 0, c_width, c_height);
$('#canvasimg').hide();
});
});
<html>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.0/jquery.min.js"></script>
<body>
<canvas id="canvas" width="400" height="400" style="position:absolute;top:10%;left:10%;border:2px solid;"></canvas>
<input type="button" value="Clear" class="canvas-clear" />
</body>
</html>
Alco check this one:
Example:
https://github.com/williammalone/Simple-HTML5-Drawing-App
Documentation:
http://www.williammalone.com/articles/create-html5-canvas-javascript-drawing-app/
This document includes following codes:-
HTML:
<canvas id="canvas" width="490" height="220"></canvas>
JS:
context = document.getElementById('canvas').getContext("2d");
$('#canvas').mousedown(function(e){
var mouseX = e.pageX - this.offsetLeft;
var mouseY = e.pageY - this.offsetTop;
paint = true;
addClick(e.pageX - this.offsetLeft, e.pageY - this.offsetTop);
redraw();
});
$('#canvas').mouseup(function(e){
paint = false;
});
$('#canvas').mouseleave(function(e){
paint = false;
});
var clickX = new Array();
var clickY = new Array();
var clickDrag = new Array();
var paint;
function addClick(x, y, dragging)
{
clickX.push(x);
clickY.push(y);
clickDrag.push(dragging);
}
//Also redraw
function redraw(){
context.clearRect(0, 0, context.canvas.width, context.canvas.height); // Clears the canvas
context.strokeStyle = "#df4b26";
context.lineJoin = "round";
context.lineWidth = 5;
for(var i=0; i < clickX.length; i++) {
context.beginPath();
if(clickDrag[i] && i){
context.moveTo(clickX[i-1], clickY[i-1]);
}else{
context.moveTo(clickX[i]-1, clickY[i]);
}
context.lineTo(clickX[i], clickY[i]);
context.closePath();
context.stroke();
}
}
And another awesome example
http://perfectionkills.com/exploring-canvas-drawing-techniques/
I used what 1083202 did but removed all the controlles, and implemented the change that KWILLIAMS suggested, that made it non sensitive to scrolling. I also made the canvas big, basically over my whole page 2000x1600 px, excepts for the margins. I did remove all the drawing tools and buttons, and used "blue" as the only color.
I put the JS-code in a separate file named myJS.js, and put that in a folder named "JS" localy:
I then used a Stylus on my Laptop to write on the tuchpad, witch works out a bit better then with the finger or mouse.
The document I use it for is kind of informal, for internal use, but it is nice to be able to put some pen strokes on it before making a pdf-file.
var canvas, ctx, flag = false,
prevX = 0,
currX = 0,
prevY = 0,
currY = 0,
dot_flag = false;
var x = "blue",
y = 3;
function init() {
canvas = document.getElementById('can');
ctx = canvas.getContext("2d");
w = canvas.width;
h = canvas.height;
canvas.addEventListener("mousemove", function (e) {
findxy('move', e)
}, false);
canvas.addEventListener("mousedown", function (e) {
findxy('down', e)
}, false);
canvas.addEventListener("mouseup", function (e) {
findxy('up', e)
}, false);
canvas.addEventListener("mouseout", function (e) {
findxy('out', e)
}, false);
}
function draw() {
ctx.beginPath();
ctx.moveTo(prevX, prevY);
ctx.lineTo(currX, currY);
ctx.strokeStyle = x;
ctx.lineWidth = y;
ctx.stroke();
ctx.closePath();
}
function findxy(res, e) {
if (res == 'down') {
prevX = currX;
prevY = currY;
currX = e.clientX - canvas.getBoundingClientRect().left;
currY = e.clientY - canvas.getBoundingClientRect().top;
flag = true;
dot_flag = true;
if (dot_flag) {
ctx.beginPath();
ctx.fillStyle = x;
ctx.fillRect(currX, currY, 2, 2);
ctx.closePath();
dot_flag = false;
}
}
if (res == 'up' || res == "out") {
flag = false;
}
if (res == 'move') {
if (flag) {
prevX = currX;
prevY = currY;
currX = e.clientX - canvas.getBoundingClientRect().left;
currY = e.clientY - canvas.getBoundingClientRect().top;
draw();
}
}
}
<html>
<body onload="init()">
<p>Below you can draw:</p>
<canvas id="can" width="750" height="1050" style="position:absolute;">Below you can write:</canvas>
</body>
Let me know if you have trouble implementing this. It uses processing.js and has features for changing colors and making the draw point larger and smaller.
<html>
<head>
<!--script librarires-->
<script type="text/javascript" src="processing.js"></script>
<script type="text/javascript" src="init.js"></script>
<!--styles -->
<style type="text/css" src="stylesheet.css">
</style>
</head>
<body>
<!--toolbox -->
<div id="draggable toolbox"></div>
<script type="application/processing">
// new script
int prevx, prevy;
int newx, newy;
boolean cliked;
color c1 = #000000;
int largeur=2;
int ps = 20;
int px = 50;
int py = 50;
void setup() {
size(500,500);
frameRate(25);
background(50);
prevx = mouseX;
prevy = mouseY;
cliked = false;
}
void draw() {
//couleur
noStroke(0);
fill(#FFFFFF);//blanc
rect(px, py, ps, ps);
fill(#000000);
rect(px, py+(ps), ps, ps);
fill(#FF0000);
rect(px, py+(ps*2), ps, ps);
fill(#00FF00);
rect(px, py+(ps*3), ps, ps);
fill(#FFFF00);
rect(px, py+(ps*4), ps, ps);
fill(#0000FF);
rect(px, py+(ps*5), ps, ps);
//largeur
fill(#FFFFFF);
rect(px, py+(ps*7), ps, ps);
fill(#FFFFFF);
rect(px, py+(ps*8), ps, ps);
stroke(#000000);
line(px+2, py+(ps*7)+(ps/2), px+(ps-2), py+(ps*7)+(ps/2));
line(px+(ps/2), py+(ps*7)+1, px+(ps/2), py+(ps*8)-1);
line(px+2, py+(ps*8)+(ps/2), px+(ps-2), py+(ps*8)+(ps/2));
if(cliked==false){
prevx = mouseX;
prevy = mouseY;
}
if(mousePressed) {
cliked = true;
newx = mouseX;
newy = mouseY;
strokeWeight(largeur);
stroke(c1);
line(prevx, prevy, newx, newy);
prevx = newx;
prevy = newy;
}else{
cliked= false;
}
}
void mouseClicked() {
if (mouseX>=px && mouseX<=(px+ps)){
//couleur
if (mouseY>=py && mouseY<=py+(ps*6)){
c1 = get(mouseX, mouseY);
}
//largeur
if (mouseY>=py+(ps*7) && mouseY<=py+(ps*8)){
largeur += 2;
}
if (mouseY>=py+(ps*8) && mouseY<=py+(ps*9)){
if (largeur>2){
largeur -= 2;
}
}
}
}
</script><canvas></canvas>
</body>
</html>
if you have background image for your canvas, you will have to make some tweaks to have it work properly because white erasing trick will hide the background.
here is a gist with the code.
<html>
<script type="text/javascript">
var canvas, canvasimg, backgroundImage, finalImg;
var mouseClicked = false;
var prevX = 0;
var currX = 0;
var prevY = 0;
var currY = 0;
var fillStyle = "black";
var globalCompositeOperation = "source-over";
var lineWidth = 2;
function init() {
var imageSrc = '/abstract-geometric-pattern_23-2147508597.jpg'
backgroundImage = new Image();
backgroundImage.src = imageSrc;
canvas = document.getElementById('can');
finalImg = document.getElementById('finalImg');
canvasimg = document.getElementById('canvasimg');
canvas.style.backgroundImage = "url('" + imageSrc + "')";
canvas.addEventListener("mousemove", handleMouseEvent);
canvas.addEventListener("mousedown", handleMouseEvent);
canvas.addEventListener("mouseup", handleMouseEvent);
canvas.addEventListener("mouseout", handleMouseEvent);
}
function getColor(btn) {
globalCompositeOperation = 'source-over';
lineWidth = 2;
switch (btn.getAttribute('data-color')) {
case "green":
fillStyle = "green";
break;
case "blue":
fillStyle = "blue";
break;
case "red":
fillStyle = "red";
break;
case "yellow":
fillStyle = "yellow";
break;
case "orange":
fillStyle = "orange";
break;
case "black":
fillStyle = "black";
break;
case "eraser":
globalCompositeOperation = 'destination-out';
fillStyle = "rgba(0,0,0,1)";
lineWidth = 14;
break;
}
}
function draw(dot) {
var ctx = canvas.getContext("2d");
ctx.beginPath();
ctx.globalCompositeOperation = globalCompositeOperation;
if(dot){
ctx.fillStyle = fillStyle;
ctx.fillRect(currX, currY, 2, 2);
} else {
ctx.beginPath();
ctx.moveTo(prevX, prevY);
ctx.lineTo(currX, currY);
ctx.strokeStyle = fillStyle;
ctx.lineWidth = lineWidth;
ctx.stroke();
}
ctx.closePath();
}
function erase() {
if (confirm("Want to clear")) {
var ctx = canvas.getContext("2d");
ctx.clearRect(0, 0, canvas.width, canvas.height);
document.getElementById("canvasimg").style.display = "none";
}
}
function save() {
canvas.style.border = "2px solid";
canvasimg.width = canvas.width;
canvasimg.height = canvas.height;
var ctx2 = canvasimg.getContext("2d");
// comment next line to save the draw only
ctx2.drawImage(backgroundImage, 0, 0);
ctx2.drawImage(canvas, 0, 0);
finalImg.src = canvasimg.toDataURL();
finalImg.style.display = "inline";
}
function handleMouseEvent(e) {
if (e.type === 'mousedown') {
prevX = currX;
prevY = currY;
currX = e.offsetX;
currY = e.offsetY;
mouseClicked = true;
draw(true);
}
if (e.type === 'mouseup' || e.type === "mouseout") {
mouseClicked = false;
}
if (e.type === 'mousemove') {
if (mouseClicked) {
prevX = currX;
prevY = currY;
currX = e.offsetX;
currY = e.offsetY;
draw();
}
}
}
</script>
<body onload="init()">
<canvas id="can" width="400" height="400" style="position:absolute;top:10%;left:10%;border:2px solid;">
</canvas>
<div style="position:absolute;top:12%;left:43%;">Choose Color</div>
<div style="position:absolute;top:15%;left:45%;width:10px;height:10px;background:green;" data-color="green" onclick="getColor(this)"></div>
<div style="position:absolute;top:15%;left:46%;width:10px;height:10px;background:blue;" data-color="blue" onclick="getColor(this)"></div>
<div style="position:absolute;top:15%;left:47%;width:10px;height:10px;background:red;" data-color="red" onclick="getColor(this)"></div>
<div style="position:absolute;top:17%;left:45%;width:10px;height:10px;background:yellow;" data-color="yellow" onclick="getColor(this)"></div>
<div style="position:absolute;top:17%;left:46%;width:10px;height:10px;background:orange;" data-color="orange" onclick="getColor(this)"></div>
<div style="position:absolute;top:17%;left:47%;width:10px;height:10px;background:black;" data-color="black" onclick="getColor(this)"></div>
<div style="position:absolute;top:20%;left:43%;">Eraser</div>
<div style="position:absolute;top:22%;left:45%;width:15px;height:15px;background:white;border:2px solid;" data-color="eraser" onclick="getColor(this)"></div>
<canvas id="canvasimg" style="display:none;" ></canvas>
<img id="finalImg" style="position:absolute;top:10%;left:52%;display:none;" >
<input type="button" value="save" id="btn" size="30" onclick="save()" style="position:absolute;top:55%;left:10%;">
<input type="button" value="clear" id="clr" size="23" onclick="erase()" style="position:absolute;top:55%;left:15%;">
</body>
</html>
I took the first answer and Changed as per my need. Now
- Works on mobile device also.
- more responsive,
- no issue with scroll
<html>
<head>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@4.6.2/dist/css/bootstrap.min.css" integrity="sha384-xOolHFLEh07PJGoPkLv1IbcEPTNtaed2xpHsD9ESMhqIYd0nLMwNLD69Npy4HI+N" crossorigin="anonymous">
<style>
.selected::before {
content: 'x';
height: 30px;
width: 30px;
left: 18px;
top: -8px;
font-size: 3rem;
position: absolute;
}
.select-colour{
height: 30px;
width: 30px;
}
</style>
</head>
<script type="text/javascript">
var canvas, ctx, flag = false,
prevX = 0,
currX = 0,
prevY = 0,
currY = 0,
dot_flag = false;
var x = "black",
y = 2;
function init() {
canvas = document.getElementById('can');
ctx = canvas.getContext("2d");
w = canvas.width;
h = canvas.height;
canvas.addEventListener("mousemove", function (e) {
findxy('move', e, '')
}, false);
canvas.addEventListener("mousedown", function (e) {
findxy('down', e, '')
}, false);
canvas.addEventListener("mouseup", function (e) {
findxy('up', e, '')
}, false);
canvas.addEventListener("mouseout", function (e) {
findxy('out', e, '')
}, false);
canvas.addEventListener("touchmove", function (e) {
findxy('move', e, 'touch')
}, false);
canvas.addEventListener("touchstart", function (e) {
findxy('down', e, 'touch')
}, false);
canvas.addEventListener("touchend", function (e) {
findxy('up', e, 'touch')
}, false);
}
function color(obj) {
x = obj.id;
if (x == "white") y = 14;
else y = 2;
var prevSelected = document.getElementsByClassName("selected");
// If it exists, remove it.
if(prevSelected.length > 0) {
prevSelected[0].classList.remove("selected");
}
document.getElementById(obj.id).classList.add("selected");
}
function draw() {
ctx.beginPath();
ctx.moveTo(prevX, prevY);
ctx.lineTo(currX, currY);
ctx.strokeStyle = x;
ctx.lineWidth = y;
ctx.stroke();
ctx.closePath();
}
function erase() {
var m = confirm("Want to clear");
if (m) {
ctx.clearRect(0, 0, w, h);
document.getElementById("canvasimg").style.display = "none";
}
}
function save() {
document.getElementById("canvasimg").style.border = "2px solid";
var dataURL = canvas.toDataURL();
document.getElementById("canvasimg").src = dataURL;
document.getElementById("canvasimg").style.display = "inline";
}
function download() {
var link = document.createElement('a');
var dataURL = canvas.toDataURL();
link.href = dataURL;
link.download = 'mydrawing.png';
document.body.appendChild(link);
link.click();
document.body.removeChild(link);
}
function findxy(res, e, source) {
if(source){
var clientX = e.changedTouches[0].clientX;
var clientY = e.changedTouches[0].clientY;
}else{
var clientX = e.clientX;
var clientY = e.clientY;
}
if (res == 'down') {
prevX = currX;
prevY = currY;
currX = clientX - canvas.getBoundingClientRect().left;
currY = clientY - canvas.getBoundingClientRect().top;
flag = true;
dot_flag = true;
if (dot_flag) {
ctx.beginPath();
ctx.fillStyle = x;
ctx.fillRect(currX, currY, 2, 2);
ctx.closePath();
dot_flag = false;
}
}
if (res == 'up' || res == "out") {
flag = false;
}
if (res == 'move') {
if (flag) {
prevX = currX;
prevY = currY;
currX = clientX - canvas.getBoundingClientRect().left;
currY = clientY - canvas.getBoundingClientRect().top;
draw();
}
}
}
</script>
<body onload="init()">
<div style="">
<div style="float: left;">
<canvas id="can" width="600" height="500" style=" border:5px solid;"></canvas>
</div>
<div style="margin-left:20px; float:left;">
<div class="row">
<div class="col-12">Choose Color</div>
<div class="col-2 pt-3"><div class="select-colour" style="background:green;" id="green" onclick="color(this)"></div></div>
<div class="col-2 pt-3"><div class="select-colour" style="background:blue;" id="blue" onclick="color(this)"></div></div>
<div class="col-2 pt-3"><div class="select-colour" style="background:red;" id="red" onclick="color(this)"></div></div>
<div class="col-2 pt-3"><div class="select-colour" style="background:yellow;" id="yellow" onclick="color(this)"></div></div>
<div class="col-2 pt-3"><div class="select-colour" style="background:orange;" id="orange" onclick="color(this)"></div></div>
<div class="col-2 pt-3"><div class="select-colour" style="background:black;" id="black" onclick="color(this)"></div></div>
<div class="col-12 pt-3 pb-3" style="">Eraser</div>
<div class="col-2 pt-3"><div class="select-colour" style="background:white;border:2px solid;" id="white" onclick="color(this)"></div></div>
</div>
<div class="row">
<div class="col-6 col-lg-12 mt-3">
<input type="button" value="Download" id="download" size="23" onclick="download()" class="btn btn-primary">
</div>
<div class="col-6 col-lg-12 mt-3">
<input type="button" value="clear" id="clr" size="23" onclick="erase()" class="btn btn-light">
</div>
</div>
</div>
</div>
</body>
</html>
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