I want to draw on a HTML Canvas using a mouse (for example, draw a signature, draw a name, ...)
How would I go about implementing this?
This question is related to
html
canvas
gesture
gesture-recognition
Here is my very simple working canvas draw and erase.
https://jsfiddle.net/richardcwc/d2gxjdva/
//Canvas_x000D_
var canvas = document.getElementById('canvas');_x000D_
var ctx = canvas.getContext('2d');_x000D_
//Variables_x000D_
var canvasx = $(canvas).offset().left;_x000D_
var canvasy = $(canvas).offset().top;_x000D_
var last_mousex = last_mousey = 0;_x000D_
var mousex = mousey = 0;_x000D_
var mousedown = false;_x000D_
var tooltype = 'draw';_x000D_
_x000D_
//Mousedown_x000D_
$(canvas).on('mousedown', function(e) {_x000D_
last_mousex = mousex = parseInt(e.clientX-canvasx);_x000D_
last_mousey = mousey = parseInt(e.clientY-canvasy);_x000D_
mousedown = true;_x000D_
});_x000D_
_x000D_
//Mouseup_x000D_
$(canvas).on('mouseup', function(e) {_x000D_
mousedown = false;_x000D_
});_x000D_
_x000D_
//Mousemove_x000D_
$(canvas).on('mousemove', function(e) {_x000D_
mousex = parseInt(e.clientX-canvasx);_x000D_
mousey = parseInt(e.clientY-canvasy);_x000D_
if(mousedown) {_x000D_
ctx.beginPath();_x000D_
if(tooltype=='draw') {_x000D_
ctx.globalCompositeOperation = 'source-over';_x000D_
ctx.strokeStyle = 'black';_x000D_
ctx.lineWidth = 3;_x000D_
} else {_x000D_
ctx.globalCompositeOperation = 'destination-out';_x000D_
ctx.lineWidth = 10;_x000D_
}_x000D_
ctx.moveTo(last_mousex,last_mousey);_x000D_
ctx.lineTo(mousex,mousey);_x000D_
ctx.lineJoin = ctx.lineCap = 'round';_x000D_
ctx.stroke();_x000D_
}_x000D_
last_mousex = mousex;_x000D_
last_mousey = mousey;_x000D_
//Output_x000D_
$('#output').html('current: '+mousex+', '+mousey+'<br/>last: '+last_mousex+', '+last_mousey+'<br/>mousedown: '+mousedown);_x000D_
});_x000D_
_x000D_
//Use draw|erase_x000D_
use_tool = function(tool) {_x000D_
tooltype = tool; //update_x000D_
}canvas {_x000D_
cursor: crosshair;_x000D_
border: 1px solid #000000;_x000D_
}<canvas id="canvas" width="800" height="500"></canvas>_x000D_
<input type="button" value="draw" onclick="use_tool('draw');" />_x000D_
<input type="button" value="erase" onclick="use_tool('erase');" />_x000D_
<div id="output"></div>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 think, other examples here are too complicated. This one is simpler and JS only...
// create canvas element and append it to document body_x000D_
var canvas = document.createElement('canvas');_x000D_
document.body.appendChild(canvas);_x000D_
_x000D_
// some hotfixes... ( ?_?)_x000D_
document.body.style.margin = 0;_x000D_
canvas.style.position = 'fixed';_x000D_
_x000D_
// get canvas 2D context and set him correct size_x000D_
var ctx = canvas.getContext('2d');_x000D_
resize();_x000D_
_x000D_
// last known position_x000D_
var pos = { x: 0, y: 0 };_x000D_
_x000D_
window.addEventListener('resize', resize);_x000D_
document.addEventListener('mousemove', draw);_x000D_
document.addEventListener('mousedown', setPosition);_x000D_
document.addEventListener('mouseenter', setPosition);_x000D_
_x000D_
// new position from mouse event_x000D_
function setPosition(e) {_x000D_
pos.x = e.clientX;_x000D_
pos.y = e.clientY;_x000D_
}_x000D_
_x000D_
// resize canvas_x000D_
function resize() {_x000D_
ctx.canvas.width = window.innerWidth;_x000D_
ctx.canvas.height = window.innerHeight;_x000D_
}_x000D_
_x000D_
function draw(e) {_x000D_
// mouse left button must be pressed_x000D_
if (e.buttons !== 1) return;_x000D_
_x000D_
ctx.beginPath(); // begin_x000D_
_x000D_
ctx.lineWidth = 5;_x000D_
ctx.lineCap = 'round';_x000D_
ctx.strokeStyle = '#c0392b';_x000D_
_x000D_
ctx.moveTo(pos.x, pos.y); // from_x000D_
setPosition(e);_x000D_
ctx.lineTo(pos.x, pos.y); // to_x000D_
_x000D_
ctx.stroke(); // draw it!_x000D_
}Googled this ("html5 canvas paint program"). Looks like what you need.
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() {_x000D_
var flag, dot_flag = false,_x000D_
prevX, prevY, currX, currY = 0,_x000D_
color = 'black', thickness = 2;_x000D_
var $canvas = $('#canvas');_x000D_
var ctx = $canvas[0].getContext('2d');_x000D_
_x000D_
$canvas.on('mousemove mousedown mouseup mouseout', function(e) {_x000D_
prevX = currX;_x000D_
prevY = currY;_x000D_
currX = e.clientX - $canvas.offset().left;_x000D_
currY = e.clientY - $canvas.offset().top;_x000D_
if (e.type == 'mousedown') {_x000D_
flag = true;_x000D_
}_x000D_
if (e.type == 'mouseup' || e.type == 'mouseout') {_x000D_
flag = false;_x000D_
}_x000D_
if (e.type == 'mousemove') {_x000D_
if (flag) {_x000D_
ctx.beginPath();_x000D_
ctx.moveTo(prevX, prevY);_x000D_
ctx.lineTo(currX, currY);_x000D_
ctx.strokeStyle = color;_x000D_
ctx.lineWidth = thickness;_x000D_
ctx.stroke();_x000D_
ctx.closePath();_x000D_
}_x000D_
}_x000D_
});_x000D_
_x000D_
$('.canvas-clear').on('click', function(e) {_x000D_
c_width = $canvas.width();_x000D_
c_height = $canvas.height();_x000D_
ctx.clearRect(0, 0, c_width, c_height);_x000D_
$('#canvasimg').hide();_x000D_
});_x000D_
});<html>_x000D_
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.0/jquery.min.js"></script>_x000D_
<body>_x000D_
<canvas id="canvas" width="400" height="400" style="position:absolute;top:10%;left:10%;border:2px solid;"></canvas>_x000D_
<input type="button" value="Clear" class="canvas-clear" />_x000D_
</body>_x000D_
</html>check this http://jsfiddle.net/ArtBIT/kneDX/. This should direct you on the right direction
Here's the most straightforward way to create a drawing application with canvas:
mousedown, mousemove, and mouseup event listener to the canvas DOMmousedown, get the mouse coordinates, and use the moveTo() method to position your drawing cursor and the beginPath() method to begin a new drawing path.mousemove, continuously add a new point to the path with lineTo(), and color the last segment with stroke().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();
};
}());
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>
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/
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>
I had to provide a simple example for this subject so I'll share here:
http://jsfiddle.net/Haelle/v6tfp2e1
class SignTool {_x000D_
constructor() {_x000D_
this.initVars()_x000D_
this.initEvents()_x000D_
}_x000D_
_x000D_
initVars() {_x000D_
this.canvas = $('#canvas')[0]_x000D_
this.ctx = this.canvas.getContext("2d")_x000D_
this.isMouseClicked = false_x000D_
this.isMouseInCanvas = false_x000D_
this.prevX = 0_x000D_
this.currX = 0_x000D_
this.prevY = 0_x000D_
this.currY = 0_x000D_
}_x000D_
_x000D_
initEvents() {_x000D_
$('#canvas').on("mousemove", (e) => this.onMouseMove(e))_x000D_
$('#canvas').on("mousedown", (e) => this.onMouseDown(e))_x000D_
$('#canvas').on("mouseup", () => this.onMouseUp())_x000D_
$('#canvas').on("mouseout", () => this.onMouseOut())_x000D_
$('#canvas').on("mouseenter", (e) => this.onMouseEnter(e))_x000D_
}_x000D_
_x000D_
onMouseDown(e) {_x000D_
this.isMouseClicked = true_x000D_
this.updateCurrentPosition(e)_x000D_
}_x000D_
_x000D_
onMouseUp() {_x000D_
this.isMouseClicked = false_x000D_
}_x000D_
_x000D_
onMouseEnter(e) {_x000D_
this.isMouseInCanvas = true_x000D_
this.updateCurrentPosition(e)_x000D_
}_x000D_
_x000D_
onMouseOut() {_x000D_
this.isMouseInCanvas = false_x000D_
}_x000D_
_x000D_
onMouseMove(e) {_x000D_
if (this.isMouseClicked && this.isMouseInCanvas) {_x000D_
this.updateCurrentPosition(e)_x000D_
this.draw()_x000D_
}_x000D_
}_x000D_
_x000D_
updateCurrentPosition(e) {_x000D_
this.prevX = this.currX_x000D_
this.prevY = this.currY_x000D_
this.currX = e.clientX - this.canvas.offsetLeft_x000D_
this.currY = e.clientY - this.canvas.offsetTop_x000D_
}_x000D_
_x000D_
draw() {_x000D_
this.ctx.beginPath()_x000D_
this.ctx.moveTo(this.prevX, this.prevY)_x000D_
this.ctx.lineTo(this.currX, this.currY)_x000D_
this.ctx.strokeStyle = "black"_x000D_
this.ctx.lineWidth = 2_x000D_
this.ctx.stroke()_x000D_
this.ctx.closePath()_x000D_
}_x000D_
}_x000D_
_x000D_
var canvas = new SignTool()canvas {_x000D_
position: absolute;_x000D_
border: 2px solid;_x000D_
}<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>_x000D_
<canvas id="canvas" width="500" height="300"></canvas>Source: Stackoverflow.com