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To get real mouse position in canvas with JavaScript, we use the canvas getBoundingClientRect method. const getMousePos = (canvas, evt) => { const rect = canvas. getBoundingClientRect(); return { x: ((evt.
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:
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.
Googled this ("html5 canvas paint program"). Looks like what you need.
http://dev.opera.com/articles/view/html5-canvas-painting/
check this http://jsfiddle.net/ArtBIT/kneDX/. This should direct you on the right direction
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();
};
}());
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