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010-lets-play.html
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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>Interactive Drawing - Let's play</title>
<meta name="viewport" content="width=device-width, minimum-scale=1.0, maximum-scale=1.0, initial-scale=1.0, user-scalable=no" />
<style>
html, body {
height: 100%;
margin: 0;
padding: 0;
}
#canvas-wrapper {
width: 100%;
height: 100%;
position: absolute;
overflow: hidden;
}
canvas {
position: absolute;
}
.CSS3Animated {
/* enable harware acceleration */
-webkit-transform: translate3d(0, 0, 0);
-moz-transform: translate3d(0, 0, 0);
-ms-transform: translate3d(0, 0, 0);
-o-transform: translate3d(0, 0, 0);
transform: translate3d(0, 0, 0);
/* animate */
-webkit-transition: all 300ms cubic-bezier(0.445, 0.045, 0.0355, 1);
-moz-transition: all 300ms cubic-bezier(0.445, 0.045, 0.0355, 1);
-ms-transition: all 300ms cubic-bezier(0.445, 0.045, 0.0355, 1);
-o-transition: all 300ms cubic-bezier(0.445, 0.045, 0.0355, 1);
transition: all 300ms cubic-bezier(0.445, 0.045, 0.0355, 1);
/* prevent flickering in animation */
-webkit-backface-visibility: hidden;
-webkit-perspective: 1000;
}
#settings {
padding: 20px 10px;
position: absolute;
}
a {
color: #000;
font-size: 14px;
font-family: Georgia;
padding: 10px;
text-decoration: none;
background: #F0F;
}
a:hover {
background: #0CC;
}
</style>
</head>
<body>
<div id="canvas-wrapper">
<canvas id="canvas">
<center>
<h1>Your browser doesn't support canvas ...</h1>
<p>Try a <a href="https://www.google.com/chrome">modern browser</a> and come back some other time.</p>
</center>
</canvas>
</div>
<div id="settings">
<a id="clear" href="#">Clear</a>
<a id="save" href="#">Save</a>
</div>
<script>
//
// MAIN SETUP ----------------------------------------------------------------
//
var canvas = document.getElementById('canvas'),
clear = document.getElementById('clear'),
save = document.getElementById('save'),
c = canvas.getContext('2d');
//
// 2D VECTOR CLASS -----------------------------------------------------------
// 2D vectors describe a point by it's xy-coordinate
//
var Vec2 = function(x, y) {
this.x = x >> 0 || 0;
this.y = y >> 0 || 0;
};
// Interpolate between 2 vectors
// AKA finding the mid-point of 2 vectors
Vec2.prototype.interpolate = function(v, amount) {
var theta = this.angle(v),
dist = this.length(v) * amount,
x = this.x - Math.cos(theta) * dist,
y = this.y - Math.sin(theta) * dist;
return new Vec2(x, y);
};
// Find the distance between 2 vectors
Vec2.prototype.length = function(v) {
var x = this.x - v.x,
y = this.y - v.y;
return Math.sqrt((x * x) + (y * y));
};
// Get angle (in radians) between 2 vectors
Vec2.prototype.angle = function(v) {
var x = this.x - v.x,
y = this.y - v.y;
return Math.atan2(y, x);
};
//
// STROKE CLASS --------------------------------------------------------------
// Each stroke is an array of Vec2-points
// Each stroke must have a minimum number of points
//
var Stroke = function() {
this.points = [];
this.minimumPoints = 5;
};
// Add points to the Stroke
Stroke.prototype.addPoints = function(p) {
// Calculate the correct vector position
// Based on the acual canvas size & position
var pixelRatio = App.getPixelRatio(),
position = App.getActualPosition(),
x = (p.clientX * pixelRatio) - position.x,
y = (p.clientY * pixelRatio) - position.y;
// Add point to array
this.points.push(new Vec2(x, y));
// If we gathered enough points
// draw a line to the previous point
if(this.points.length > 2 * this.minimumPoints) this.draw(this.points.length - 1);
};
// Draw a line to the previous point
Stroke.prototype.draw = function(i) {
var p1 = this.points[i - (2 * this.minimumPoints)],
p2 = this.points[i - this.minimumPoints],
p3 = this.points[i],
// Calculate Bezier anchors
m1 = p1.interpolate(p2, 0.5),
m2 = p2.interpolate(p3, 0.5),
// Moving speed
speed = m1.length(m2) * 0.25 * (i%10 === 0 ? 3 : 1);
// Default line settings
c.lineWidth = speed * App.getPixelRatio();
c.strokeStyle = 'rgba('+ ((p2.x / App.getSize() * 255) >> 0) +', '+ ((Math.random() * 255) >> 0) +', '+ ((p2.y / App.getSize() * 255) >> 0) +', 1)';
c.globalCompositeOperation = i%5 === 0 ? 'lighter' : 'source-over';
// Dropshadow
c.shadowOffsetX = speed;
c.shadowOffsetY = speed;
c.shadowBlur = 25;
c.shadowColor = 'rgba(0, 0, 0, 0.3)';
// Draw
c.beginPath( );
c.moveTo(m1.x, m1.y);
c.quadraticCurveTo(p2.x, p2.y, m2.x, m2.y);
c.stroke();
// Drawing styles, composite blending, ...
// http://joshondesign.com/p/books/canvasdeepdive/toc.html
};
//
// UTILITIES -----------------------------------------------------------------
//
var Utils = {};
// Debounce method to guarantee that a callback method will only ever
// be executed once in a given timeframe (<-> browser resize event in IE which fires continuously)
// http://www.paulirish.com/2009/throttled-smartresize-jquery-event-handler
// http://davidwalsh.name/function-debounce
// Note: if Underscore/Lo-Dash is included in your project you can use _.debounce(callback, wait)
// http://lodash.com/docs#debounce
Utils.debounce = function(callback, wait) {
var timeout = null;
return function() {
var obj = this, args = arguments;
var delayed = function() {
callback.apply(obj, args);
timeout = null;
};
if(timeout) clearTimeout(timeout);
timeout = setTimeout(delayed, wait);
};
};
// Get CSS3 support
Utils.checkCSS3Support = function(prop) {
var vendors = ['webkit', 'Moz', 'O', 'ms', ''], i = vendors.length;
while(i--) if((vendors[i] + prop) in document.body.style && !Utils.isIE9()) return vendors[i] + prop;
return false;
};
// Check if we're on IE9
// IE9 has CSS3 properties but 'transitions' are not supported
// http://quirksmode.org/js/detect.html
Utils.isIE9 = function() {
var mode = document.documentMode, lang = window.navigator.systemLanguage;
return lang && ( !mode || mode === 9 ) ? true : false;
};
//
// APPLICATION ---------------------------------------------------------------
//
var App = (function() {
var size, position, pixelRatio, retinaSize, CSS3Transform = Utils.checkCSS3Support('Transform');
// INIT
var init = function() {
// Our canvas is a square taking the biggest side as its base
size = screen.width < screen.height ? screen.height : screen.width;
// Enable retina support by scaling the canvas x 2,
// while setting the CSS property to its normal size (the img-trick)
// For this we need to ge the pixelratio of the device
// On retina devices this has a value of 2, setting it to 1.99 however speeds up drawing
pixelRatio = window.devicePixelRatio && window.devicePixelRatio === 2 ? 1.99 : 1;
// Now, let's set the canvas size
// Remember: the canvas is a square, taking its biggest size as its base x retina
// To support retina we need to update the CSS-values of the canvas
canvas.width = size * pixelRatio;
canvas.height = size * pixelRatio;
canvas.style.width = size +'px';
canvas.style.height = size +'px';
// Set canvas position
position = new Vec2();
// When scaling-up the canvas, all touch-positions will be wrong
// We can fix this by calculating touch-positions against the actual position
actualPosition = new Vec2();
// Set canvas position
this.resizeCanvas();
// Add CSS3 animations after the first resize-event
setTimeout(function() { canvas.className = 'CSS3Animated'; }, 1000);
};
// RESIZE WINDOW
// Instead of auto-clearing the canvas onResize
// We move the entire canvas to a new position
var resizeCanvas = function() {
// Center the canvas
position.x = (window.innerWidth - size) * .5 >> 0;
position.y = (window.innerHeight - size) * .5 >> 0;
// Keep track of its real position
// to calculate touch-positions against on retina-devices
actualPosition.x = position.x * pixelRatio;
actualPosition.y = position.y * pixelRatio;
// Set canvas position
// Use CSS3 Translation for hardware acceleration
// Note: not supported on Opera Mini - http://caniuse.com/#search=translate
if(CSS3Transform) canvas.style[CSS3Transform] = 'translate3d('+ position.x +'px, '+ position.y +'px, 0)';
else {
canvas.style.left = position.x +'px';
canvas.style.top = position.y +'px';
}
};
// CLEAR CANVAS
// Remove all strokes from the canvas
var clearCanvas = function() {
c.clearRect(0, 0, canvas.width, canvas.height);
};
// SAVE CANVAS
// Take a snapshot of the canvas & save it
// Output: Base64 Encoded String
// http://greenethumb.com/article/1429/user-friendly-image-saving-from-the-canvas
// Basic code: window.open( canvas.toDataURL('image/png') );
//
// Force download by replacing the extension
// Note: downloaded files don't have a file extension
// var data = canvas.toDataURL("image/png").replace("image/png", "image/octet-stream");
// window.location.href = data;
//
// Support for Base64 Encoded saving
// IE9: not sufficient to render images (filesize is limited on IE)
// Chrome: memory issues with large images (browser crashes)
// iPad (with retina) takes sometime to render (js is not as fast as on desktop)
// iPad Standalone version: doesn't have window.open event
//
// Better solution
// Export the Base64 Encoded string to PHP (or other server-side language)
// and store it on the server via an AJAX call
// http://stackoverflow.com/questions/11511511/how-to-save-a-png-image-server-side-from-a-base64-data-string
var saveCanvas = function() {
window.open( canvas.toDataURL('image/png') );
};
//
// PUBLIC API ------------------------------------------------------------
//
return {
getActualPosition : function() { return actualPosition; },
getPixelRatio : function() { return pixelRatio; },
getSize : function() { return size; },
init : init,
resizeCanvas : resizeCanvas,
clearCanvas : clearCanvas,
saveCanvas : saveCanvas
}
}());
//
// EVENT MANAGER -------------------------------------------------------------
//
var Events = (function() {
//
// TOUCH DEVICES ---------------------------------------------------------
//
if('ontouchstart' in document) {
// To support multitouch drawing, we will need
// to keep track of all active touches
var activeTouches = [],
// Each touch will create a new Stroke()
// To support multitouch we need a way to identify individual strokes
// So we store all strokes in an array
strokes = [],
// And create a Touch class which links
// the current active touch to a specific stroke
Touch = function(id) {
this.touchID = id;
this.strokeID = strokes.length;
strokes.push(new Stroke());
};
// CANVAS ONTOUCHDOWN
// For each touch we create a new Touch instance and
// store in the activeTouches array
// Note: In order to track touchMove events correctly
// use 'e.changedTouches' instead of 'e.touches'
// https://developer.mozilla.org/en-US/docs/Web/Reference/Events/touchmove
canvas.addEventListener('touchstart', function(e) {
var i = e.changedTouches.length;
while(i--) activeTouches.push(new Touch( e.changedTouches[i].identifier ));
}, false);
// START DRAWING ONTOUCHMOVE
// For each touch, search the corresponding Touch instance
// in the activeTouches array & add points to the referenced Stroke
canvas.addEventListener('touchmove', function(e) {
var i = e.changedTouches.length; while(i--) {
var j = activeTouches.length; while(j--) {
if( e.changedTouches[i].identifier === activeTouches[j].touchID ) {
strokes[ activeTouches[j].strokeID ].addPoints( e.changedTouches[i] );
}
}
}
// Important: disable elastic scrolling
// by killing the default behaviour
e.preventDefault();
}, false);
// STOP DRAWING ONTOUCHEND
// Search the corresponding Touch instance
// and remove it from the activeTouches array
canvas.addEventListener('touchend', function(e) {
var i = e.changedTouches.length; while(i--) {
var j = activeTouches.length; while(j--) {
if( e.changedTouches[i].identifier === activeTouches[j].strokeID ) {
activeTouches.splice(j, 1);
}
}
}
}, false);
// BUTTON EVENTS
clear.addEventListener('touchstart', App.clearCanvas, false);
save.addEventListener('touchstart', App.saveCanvas, false );
// Important: disable elastic scrolling
// by killing the default behaviour
clear.addEventListener('touchmove', function(e) { e.preventDefault(); }, false);
save.addEventListener('touchmove', function(e) { e.preventDefault(); }, false);
// BROWSER RESIZE
// Add a default resize event as well
// in case window.orientation is not supported
// http://davidwalsh.name/orientation-change
if(window.orientation) window.onorientationchange = Utils.debounce(App.resizeCanvas, 100);
else window.onresize = Utils.debounce(App.resizeCanvas, 100);
//
// DESKTOP ---------------------------------------------------------------
//
} else {
// START DRAWING
// Each mousedown event starts a new Stroke()
// and has its own mousemove, mouseup & mouseout event
canvas.addEventListener('mousedown', function(e) {
var stroke = new Stroke();
// Add points to the stroke onMouseMove
canvas.addEventListener('mousemove', onMouseMove = function(e) {
stroke.addPoints(e);
}, false);
// Stop drawing on mouseUp
// by removing the mousemove listener
canvas.addEventListener('mouseup', function(e) {
canvas.removeEventListener('mousemove', onMouseMove, false);
}, false);
// Important: when moving outside the canvas the mouseup event never gets called
// So we need to add an additional mouseOut event which clears the mouseMove event
canvas.addEventListener('mouseout', function(e) {
canvas.removeEventListener('mousemove', onMouseMove, false);
}, false);
// Disable the cursor going into 'select'
e.preventDefault();
});
// BUTTON EVENTS
clear.addEventListener('mousedown', App.clearCanvas, false);
save.addEventListener('mousedown', App.saveCanvas, false );
// Important: disable # popping up in the url
// by killing the default behaviour
clear.addEventListener('click', function(e) { e.preventDefault(); }, false);
save.addEventListener('click', function(e) { e.preventDefault(); }, false);
// BROWSER RESIZE
window.onresize = Utils.debounce(App.resizeCanvas, 100);
}
}());
// START THE APPLICATION
App.init();
</script>
</body>
</html>