javascript 烟火 fireworks demo 分析

之前看到一个用javascript写的烟火demo，非常酷，今天分析了一下canvas的部分，挺有意思。

大体上分为这么几步：

第一步收集字母的矩阵点
第二步lauch 每一个点
第二步建立sparks
第四步show throwing点和sparks

源代码如下：

/*
* fireworks.js - Kenneth Kufluk (http://kenneth.kufluk.com/)
* http://js-fireworks.appspot.com/
* MIT (X11) Licensed

Copyright (c) 2010 Kenneth Kufluk


Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:


The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.


THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.

*
*/
$(document).ready(function(){



// focus on the input box
try {
$('#firetext').get(0).focus();
} catch (ignore) {
}


// reload the page when it's resized
var resizeTimer = null;
$(window).bind('resize', function() {
if (document.all) return;
if (resizeTimer) clearTimeout(resizeTimer);
resizeTimer = setTimeout("location.reload()", 100);
});


// finally, all is ready, so kick off the firework display
var params = location.search;
var message = "";
if (params.match('msg=')) {
// change the message if set in the page url
message = unescape(params.split('?msg=')[1]);
$('#firetext').val(message);
}
FireworkDisplay.launchText();


});




// configure the sliders
$(document).ready(function(){
$("#slider_firework_speed").slider({
slide: function(event, ui) {
FireworkDisplay.FIREWORK_SPEED = ui.value;
},
value: FireworkDisplay.FIREWORK_SPEED,
max: 5,
step: 0.1,
orientation: 'vertical'
});
$("#slider_fragment_spread").slider({
slide: function(event, ui) {
FireworkDisplay.FRAGMENT_SPREAD = ui.value;
},
value: FireworkDisplay.FRAGMENT_SPREAD,
max: 20,
orientation: 'vertical'
});
$("#slider_gravity").slider({
slide: function(event, ui) {
FireworkDisplay.GRAVITY = ui.value;
},
value: FireworkDisplay.GRAVITY,
step: 0.1,
min: -10,
max: 20,
orientation: 'vertical'
});
});




FireworkDisplay = {
GRAVITY : 5,
FRAME_RATE : 30,
DEPLOYMENT_RATE : 1,
FIREWORK_SPEED : 2,
DISPERSION_WIDTH : 1,
DISPERSION_HEIGHT : 2,
FIREWORK_PAYLOAD : 30,
FRAGMENT_SPREAD : 8,
TEXT_LINE_HEIGHT : 70,
FIREWORK_READY : 0,
FIREWORK_LAUNCHED : 1,
FIREWORK_EXPLODED : 2,
FIREWORK_FRAGMENT : 3,
canvas : 0,
canvaswidth : 0,
canvasheight : 0,
ctx : 0,
blockPointer : 0,
fireworks : [],
allBlocks : new Array(),
gameloop : 0,
launchText : function() {

this.fireworks = [];
this.blockPointer = 0;
clearTimeout(this.gameloop);
//CANVAS
this.canvas = $("#cv").get(0);
if (typeof G_vmlCanvasManager != "undefined") {
this.canvas = G_vmlCanvasManager.initElement(this.canvas);
}
this.ctx = this.canvas.getContext("2d");
this.ctx.clearRect(0, 0, this.canvas.width, this.canvas.height);
this.ctx.lineWidth = "2";
this.ctx.strokeStyle = "rgb(255, 255, 255)";
this.canvaswidth = $(window).width();
this.canvasheight = $(window).height();


$(this.canvas).bind('click', function() {
$('#form').fadeIn('slow');
});

var text = $('#firetext').val();

/* caculate max width for each character*/
var totalHeightOffset = 0;
var totalWidthOffset = new Array();
var widthCounter = 0;
totalWidthOffset[widthCounter] = 0;
for (var i=0;i<text.length;i++) {
if (text.charAt(i)==' ') {
totalHeightOffset += this.TEXT_LINE_HEIGHT;
widthCounter++;
totalWidthOffset[widthCounter] = 0;
} else {
var maxWidthOffset = 0;
for (var j=0;j<FONT_FIREWORK[text.charAt(i)].length;j++) {
var chararr = FONT_FIREWORK[text.charAt(i)][j];
maxWidthOffset = Math.max(maxWidthOffset, chararr[0]);
}
totalWidthOffset[widthCounter] += maxWidthOffset + 40;
}
}
console.info(totalHeightOffset,totalWidthOffset);


/* caculate absolute position for each points inside each character*/
this.allBlocks = new Array();
var windowHeight = $(window).height();
var offsetTop = totalHeightOffset;
offsetTop += (windowHeight-totalHeightOffset)/6;
var offsetLeft = 0;
var heightOffsetCount = 0;
for (var i=0;i<text.length;i++) {
if (text.charAt(i)==' ') {
heightOffsetCount++;
offsetTop = offsetTop - this.TEXT_LINE_HEIGHT;
offsetLeft = 0;
} else {
var maxWidthOffset = 0;
for (var j=0;j<FONT_FIREWORK[text.charAt(i)].length;j++) {
var chararr = FONT_FIREWORK[text.charAt(i)][j];
this.allBlocks[this.allBlocks.length] = [(chararr[0]+offsetLeft)-(totalWidthOffset[heightOffsetCount]/2), chararr[1]-offsetTop];
maxWidthOffset = Math.max(maxWidthOffset, chararr[0]);
}
offsetLeft += maxWidthOffset+40; //plus character spacing
}
}


this.gameloop = setInterval("FireworkDisplay.updateDisplay()", 1000/this.FRAME_RATE);

this.addFireworks();

$('#form').fadeOut('slow');
},
updateDisplay : function() {
this.ctx.clearRect(0, 0, this.canvaswidth, this.canvasheight);
var firecount = 0;
for (var i=0;i<this.fireworks.length;i++) {
if (this.fireworks[i]==null) continue;
if (this.fireworks[i].status!=this.FIREWORK_EXPLODED) {
firecount++;
}
this.displayFirework(this.fireworks[i]);
}
if (firecount == 0) {
$('#form').fadeIn('slow');
}
$('#fireCount').html(firecount);
},
/*add a point to blockPointer*/
addFireworks : function() {
if (this.blockPointer>=this.allBlocks.length) {
return;
}
var fw = this.fireworks[this.fireworks.length] = new Firework(this.fireworks.length);
var targetx = this.allBlocks[this.blockPointer][0];
targetx = (((targetx)) / 300) * this.DISPERSION_HEIGHT;
var targety = this.allBlocks[this.blockPointer][1];
targety = (((10-targety) / 100) * this.DISPERSION_WIDTH) + 3.5;
this.launchFirework(fw, targetx, targety);
this.blockPointer++;
setTimeout("FireworkDisplay.addFireworks()", 1000/this.DEPLOYMENT_RATE);
},


launchFirework : function(fw, dispersion, speed) {
fw.dx = dispersion;
fw.dy = speed;
fw.status = this.FIREWORK_LAUNCHED;
},
displayFirework : function(fw, speed) {
if (fw.y<0) this.destroyFirework(fw);
/*draw the point*/
if (fw.status==this.FIREWORK_EXPLODED) {
this.ctx.beginPath();
this.ctx.fillStyle = "rgb(200, 200, 200)";
var radius = 3; // Arc radius
var startAngle = 0; // Starting point on circle
var endAngle = Math.PI*2; // End point on circle
var anticlockwise = true; // clockwise or anticlockwise
this.ctx.arc(fw.x, this.canvas.height-fw.y, radius, startAngle, endAngle, anticlockwise);
this.ctx.fill();
return;
}

fw.colour = "rgb(80, 80, 80)";
this.ctx.strokeStyle = fw.colour;
var forces = {x:0,y:-0.05};
if (fw.status==this.FIREWORK_FRAGMENT) {
forces.y = this.GRAVITY/-100;
fw.colour = "rgb("+Math.round(fw.r*fw.brightness)+", "+Math.round(fw.g*fw.brightness)+", "+Math.round(fw.b*fw.brightness)+")";
this.ctx.strokeStyle = fw.colour;
fw.brightness-=5;
if (fw.brightness<0) this.destroyFirework(fw);
}
/* make the explode effect */
if (fw.dy<-1 && fw.status==this.FIREWORK_LAUNCHED) {
this.explodeFirework(fw);
}
/* make the throwing effect */
fw.start = {x:fw.x, y:fw.y};
//apply accelerations
fw.dx += forces.x*this.FIREWORK_SPEED;
fw.dy += forces.y*this.FIREWORK_SPEED;
//apply velocities
fw.x += fw.dx*this.FIREWORK_SPEED;
fw.y += fw.dy*this.FIREWORK_SPEED;
//show
//all throwing and exploding is been drawed here
if (fw.previous) {
this.ctx.beginPath();
this.ctx.moveTo(fw.previous.x, this.canvas.height-fw.previous.y);
this.ctx.lineTo(fw.x, this.canvas.height-fw.y);
this.ctx.stroke();
this.ctx.closePath();
}
fw.previous = {x:fw.start.x, y:fw.start.y};
},

explodeFirework : function(fw, speed) {
fw.status = this.FIREWORK_EXPLODED;
fw.r = (Math.random() /2) + 0.5;
fw.g = (Math.random() /2) + 0.5;
fw.b = (Math.random() /2) + 0.5;
fw.brightness = 200;
this.ctx.strokeStyle = "rgb(200, 200, 200)";
// add the fragments
var frags = Math.random() * this.FIREWORK_PAYLOAD;
for (var i=0;i<frags;i++) {
var spark = this.fireworks[this.fireworks.length] = new Firework(this.fireworks.length);
spark.x = fw.x;
spark.y = fw.y;
spark.r = fw.r;
spark.g = fw.g;
spark.b = fw.b;
spark.status = this.FIREWORK_FRAGMENT;
this.disperseFirework(spark, Math.random()*this.FRAGMENT_SPREAD);
}
},
disperseFirework : function(fw, speed) {
fw.dx = speed * (0.5-Math.random());
fw.dy = speed * (0.5-Math.random()) + 1;
},
destroyFirework : function(fw) {
this.fireworks[fw.index] = null;
},

}


Firework = function(index) {
this.index = index;
this.dx = 0;
this.dy = 0;
this.x = FireworkDisplay.canvaswidth/2;
this.y = 0;
this.status = FireworkDisplay.FIREWORK_READY;
this.brightness = 255;
this.r = 1;
this.g = 1;
this.b = 1;
this.start = {x:0, y:0};
this.previous = 0;
}




// Home-made point-based font.
/*


0--->
|
|
|


*/
var FONT_FIREWORK = {"!":[[5,-40],[5,-30],[5,-20],[5,0]],"\"":[[20,-40],[20,-30],[5,-40],[5,-30]],"#":[[35,-40],[45,-30],[35,-30],[15,-40],[25,-30],[35,-20],[45,-10],[15,-30],[35,-10],[5,-30],[15,-20],[25,-10],[35,0],[15,-10],[5,-10],[15,0]],"%":[[45,-40],[35,-30],[15,-40],[45,-10],[5,-40],[15,-30],[25,-20],[35,-10],[45,0],[5,-30],[35,0],[15,-10],[5,0]],"&":[[35,-40],[25,-40],[35,-30],[15,-40],[35,-20],[15,-30],[25,-20],[15,-20],[25,-10],[35,0],[5,-20],[25,0],[5,-10],[15,0],[25,10],[5,0]],"'":[[5,-40],[5,-30]],"(":[[15,-40],[5,-30],[5,-20],[5,-10],[15,0]],")":[[5,-40],[15,-30],[15,-20],[15,-10],[5,0]],"*":[[25,-40],[5,-40],[15,-30],[25,-20],[5,-20]],"+":[[20,-40],[35,-20],[20,-30],[25,-20],[15,-20],[20,-10],[5,-20],[20,0]],",":[[5,0],[5,10]],"-":[[35,-20],[25,-20],[15,-20],[5,-20]],"-":[[35,-20],[25,-20],[15,-20],[5,-20]],".":[[5,0]],"/":[[45,-40],[35,-30],[25,-20],[15,-10],[5,0]],":":[[5,-30],[5,-10]],";":[[5,-30],[5,-10],[5,0]],"<":[[15,-25],[5,-15],[15,-5]],"=":[[35,-30],[25,-30],[15,-30],[35,-10],[5,-30],[25,-10],[15,-10],[5,-10]],">":[[5,-25],[15,-15],[5,-5]],"?":[[35,-40],[25,-40],[35,-30],[15,-40],[35,-20],[5,-40],[25,-20],[15,-20],[15,0]],"@":[[35,-30],[25,-40],[15,-40],[35,-20],[25,-20],[35,-10],[5,-30],[35,0],[15,-15],[5,-20],[25,0],[15,-5],[5,-10],[15,5],[5,0]],"A":[[35,-30],[25,-40],[15,-40],[35,-20],[25,-20],[35,-10],[5,-30],[15,-20],[35,0],[5,-20],[5,-10],[5,0]],"B":[[25,-40],[15,-40],[25,-30],[35,-20],[5,-40],[25,-20],[35,-10],[5,-30],[15,-20],[35,0],[5,-20],[25,0],[5,-10],[15,0],[5,0]],"C":[[35,-40],[25,-40],[15,-40],[5,-30],[35,0],[5,-20],[25,0],[5,-10],[15,0]],"D":[[35,-30],[25,-40],[15,-40],[35,-20],[5,-40],[35,-10],[5,-30],[5,-20],[25,0],[5,-10],[15,0],[5,0]],"E":[[35,-40],[25,-40],[15,-40],[5,-40],[25,-20],[5,-30],[15,-20],[35,0],[5,-20],[25,0],[5,-10],[15,0],[5,0]],"F":[[35,-40],[25,-40],[15,-40],[5,-40],[25,-20],[5,-30],[15,-20],[5,-20],[5,-10],[5,0]],"G":[[35,-40],[25,-40],[15,-40],[35,-20],[25,-20],[35,-10],[5,-30],[35,0],[5,-20],[25,0],[5,-10],[15,0]],"H":[[35,-40],[35,-30],[35,-20],[5,-40],[25,-20],[35,-10],[5,-30],[15,-20],[35,0],[5,-20],[5,-10],[5,0]],"I":[[25,-40],[15,-40],[5,-40],[15,-30],[15,-20],[15,-10],[25,0],[15,0],[5,0]],"J":[[35,-40],[25,-40],[35,-30],[35,-20],[35,-10],[25,0],[5,-10],[15,0]],"K":[[35,-40],[25,-30],[5,-40],[25,-20],[35,-10],[5,-30],[15,-20],[35,0],[5,-20],[5,-10],[5,0]],"L":[[5,-40],[5,-30],[35,0],[5,-20],[25,0],[5,-10],[15,0],[5,0]],"M":[[35,-40],[35,-30],[25,-30],[35,-20],[5,-40],[15,-30],[35,-10],[20,-20],[5,-30],[35,0],[5,-20],[5,-10],[5,0]],"N":[[35,-40],[35,-30],[35,-20],[5,-40],[15,-30],[25,-20],[35,-10],[5,-30],[35,0],[5,-20],[5,-10],[5,0]],"O":[[35,-30],[25,-40],[15,-40],[35,-20],[35,-10],[5,-30],[5,-20],[25,0],[5,-10],[15,0]],"P":[[35,-30],[25,-40],[15,-40],[5,-40],[25,-20],[5,-30],[15,-20],[5,-20],[5,-10],[5,0]],"Q":[[35,-30],[25,-40],[15,-40],[35,-20],[35,-10],[5,-30],[25,-10],[35,0],[5,-20],[25,0],[5,-10],[15,0]],"R":[[35,-30],[25,-40],[15,-40],[5,-40],[25,-20],[35,-10],[5,-30],[15,-20],[35,0],[5,-20],[5,-10],[5,0]],"S":[[35,-35],[25,-40],[15,-40],[35,-15],[25,-20],[5,-35],[35,-5],[15,-20],[5,-25],[25,0],[15,0],[5,-5]],"T":[[35,-40],[25,-40],[15,-40],[20,-30],[5,-40],[20,-20],[20,-10],[20,0]],"U":[[35,-40],[35,-30],[35,-20],[5,-40],[35,-10],[5,-30],[5,-20],[25,0],[5,-10],[15,0]],"V":[[35,-40],[35,-30],[35,-20],[5,-40],[5,-30],[25,-10],[5,-20],[15,-10],[20,0]],"W":[[35,-40],[35,-30],[20,-40],[35,-20],[20,-30],[5,-40],[35,-10],[20,-20],[5,-30],[35,0],[20,-10],[5,-20],[25,0],[5,-10],[15,0]],"X":[[35,-40],[25,-30],[5,-40],[15,-30],[20,-20],[25,-10],[35,0],[15,-10],[5,0]],"Y":[[35,-40],[35,-30],[5,-40],[25,-20],[5,-30],[15,-20],[20,-10],[20,0]],"Z":[[35,-40],[25,-40],[15,-40],[25,-30],[5,-40],[20,-20],[35,0],[15,-10],[25,0],[15,0],[5,0]],"_":[[45,0],[35,0],[25,0],[15,0],[5,0]],"a":[[25,-30],[35,-20],[15,-30],[35,-10],[25,-15],[5,-30],[35,0],[15,-15],[25,0],[5,-10],[15,0]],"b":[[25,-30],[35,-20],[5,-40],[15,-30],[35,-10],[5,-30],[5,-20],[25,0],[5,-10],[15,0],[5,0]],"c":[[35,-30],[25,-30],[15,-30],[35,0],[5,-20],[25,0],[5,-10],[15,0]],"d":[[35,-40],[35,-30],[25,-30],[35,-20],[15,-30],[35,-10],[35,0],[5,-20],[25,0],[5,-10],[15,0]],"e":[[25,-30],[35,-20],[15,-30],[25,-15],[35,0],[15,-15],[5,-20],[25,0],[5,-10],[15,0]],"f":[[25,-40],[15,-40],[25,-20],[5,-30],[15,-20],[5,-20],[5,-10],[5,0]],"g":[[35,-30],[25,-30],[35,-20],[15,-30],[35,-10],[25,-10],[35,0],[5,-20],[15,-10],[25,10],[15,10],[5,10]],"h":[[5,-40],[25,-20],[35,-10],[5,-30],[15,-20],[35,0],[5,-20],[5,-10],[5,0]],"i":[[5,-40],[5,-20],[5,-10],[5,0]],"j":[[15,-40],[15,-20],[15,-10],[15,0],[5,10]],"k":[[35,-30],[5,-40],[25,-20],[35,-10],[5,-30],[15,-20],[35,0],[5,-20],[5,-10],[5,0]],"l":[[5,-40],[5,-30],[5,-20],[5,-10],[15,0]],"m":[[35,-30],[45,-20],[25,-30],[45,-10],[15,-30],[25,-20],[45,0],[5,-30],[25,-10],[5,-20],[25,0],[5,-10],[5,0]],"n":[[25,-30],[35,-20],[15,-30],[35,-10],[5,-30],[35,0],[5,-20],[5,-10],[5,0]],"o":[[25,-30],[35,-20],[15,-30],[35,-10],[5,-20],[25,0],[5,-10],[15,0]],"p":[[25,-30],[35,-20],[15,-30],[35,-10],[5,-30],[5,-20],[25,0],[5,-10],[15,0],[5,0],[5,10]],"q":[[35,-30],[25,-30],[35,-20],[15,-30],[35,-10],[35,0],[5,-20],[25,0],[35,10],[5,-10],[15,0]],"r":[[35,-30],[25,-30],[5,-30],[15,-20],[5,-20],[5,-10],[5,0]],"s":[[35,-30],[25,-30],[15,-30],[35,-10],[25,-15],[15,-15],[5,-20],[25,0],[15,0],[5,0]],"t":[[25,-30],[5,-40],[15,-30],[5,-30],[5,-20],[25,0],[5,-10],[15,0]],"u":[[35,-30],[35,-20],[35,-10],[5,-30],[35,0],[5,-20],[25,0],[5,-10],[15,0]],"v":[[35,-30],[35,-20],[5,-30],[25,-10],[5,-20],[15,-10],[20,0]],"w":[[35,-30],[35,-20],[20,-30],[35,-10],[20,-20],[5,-30],[35,0],[20,-10],[5,-20],[25,0],[5,-10],[15,0]],"x":[[35,-30],[25,-20],[5,-30],[15,-20],[25,-10],[35,0],[15,-10],[5,0]],"y":[[35,-30],[35,-20],[35,-10],[5,-30],[25,-10],[35,0],[5,-20],[15,-10],[25,10],[15,10]],"z":[[35,-30],[25,-30],[15,-30],[25,-20],[5,-30],[35,0],[15,-10],[25,0],[15,0],[5,0]],"0":[[35,-30],[25,-40],[15,-40],[35,-20],[35,-10],[15,-25],[25,-15],[5,-30],[5,-20],[25,0],[5,-10],[15,0]],"1":[[15,-40],[15,-30],[5,-30],[15,-20],[15,-10],[15,0]],"2":[[35,-35],[25,-40],[35,-25],[15,-40],[25,-20],[5,-35],[15,-20],[35,0],[25,0],[5,-10],[15,0],[5,0]],"3":[[25,-40],[35,-30],[15,-40],[5,-40],[25,-20],[35,-10],[15,-20],[25,0],[15,0],[5,0]],"4":[[35,-40],[35,-30],[35,-20],[5,-40],[25,-20],[35,-10],[5,-30],[15,-20],[35,0],[5,-20]],"5":[[35,-40],[25,-40],[15,-40],[35,-15],[5,-40],[25,-20],[35,-5],[5,-30],[15,-20],[5,-20],[25,0],[15,0],[5,0]],"6":[[35,-40],[25,-40],[15,-40],[35,-20],[25,-20],[35,-10],[5,-30],[15,-20],[5,-20],[25,0],[5,-10],[15,0]],"7":[[35,-40],[35,-30],[25,-40],[15,-40],[5,-40],[25,-20],[5,-30],[25,-10],[25,0]],"8":[[35,-35],[25,-40],[35,-25],[15,-40],[35,-15],[25,-20],[5,-35],[35,-5],[15,-20],[5,-25],[25,0],[5,-15],[15,0],[5,-5]],"9":[[35,-30],[25,-40],[15,-40],[35,-20],[25,-20],[35,-10],[5,-30],[15,-20],[5,-20],[25,0],[15,0],[5,0]]};