HTML5 Canvas开发迷宫游戏例子
本文介绍如何使用Canvas画布制作一个简单的迷宫游戏：用户按下方向键时，笑脸图标会沿相应的方向移动（移动时有动画效果），遇到墙壁时（碰撞检测）就会停下来。
1，在线样例
加载困难迷宫 加载简单迷宫
2，实现原理
（1）迷宫的生成：我们这里是使用一幅迷宫图片，然后把整幅图绘制到画布上。
（2）通过设置 window.onkeydown 的响应函数 processKey()，当用户按下方向键的时候，根据键码调整笑脸各方向上的速度。
（3）drawFrame() 函数每10毫秒刷新画布，如果笑脸有速度则移动并绘制轨迹，同时作碰撞检测。最后还会检测笑脸是否到底部，到了话弹出成功消息框。
3，碰撞检测
这里使用的是基于像素颜色碰撞检测，我们取笑脸所在区域的像素块（在笑脸四周再稍微扩展一点），判断其中是否有黑色像素，有的话则说明撞墙了。
4，完整代码
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>hangge.com</title>
<style>
canvas {
border: 6px double black;
background: white;
}
img {
display: none;
}
button {
padding: 3px;
}
</style>
<script>
var canvas;
var context;
// 记录笑脸图标的当前位置
var x = 0;
var y = 0;
// 记录笑脸在x轴和y轴方向上每一帧要移动多少像素
var dx = 0;
var dy = 0;
window.onload = function() {
// 设置画布
canvas = document.getElementById("canvas");
context = canvas.getContext("2d");
// 绘制迷宫背景
drawMaze('http://www.hangge.com/blog_uploads/201602/2016022313460193716.png', 5, 5);
// 当用户按下键盘上的键时，运行processKey()函数
window.onkeydown = processKey;
};
// timer引用，这样重新加载迷宫的时候可以很方便地停止绘制
var timer;
function drawMaze(mazeFile, startingX, startingY) {
// 先停止绘制
clearTimeout(timer);
// 停止笑脸
dx = 0;
dy = 0;
// 加载迷宫图片
var imgMaze = new Image();
imgMaze.onload = function() {
// 调整画布大小以适应迷宫图片
canvas.width = imgMaze.width;
canvas.height = imgMaze.height;
// 绘制迷宫
context.drawImage(imgMaze, 0,0);
// 绘制笑脸
x = startingX;
y = startingY;
var imgFace = document.getElementById("face");
context.drawImage(imgFace, x, y);
context.stroke();
// 10毫秒后绘制下一帧
timer = setTimeout(drawFrame, 10);
};
imgMaze.src = mazeFile;
}
function processKey(e) {
// 如果笑脸在移动，停止
dx = 0;
dy = 0;
// 按下了向上键，向上移动
if (e.keyCode == 38) {
dy = -1;
}
// 按下了向下键，向下移动
if (e.keyCode == 40) {
dy = 1;
}
// 按下了向左键，向左移动
if (e.keyCode == 37) {
dx = -1;
}
// 按下了向右键，向右移动
if (e.keyCode == 39) {
dx = 1;
}
}
function checkForCollision() {
// 取得笑脸所在的像素块，再稍微扩展一点
var imgData = context.getImageData(x-1, y-1, 15+2, 15+2);
var pixels = imgData.data;
// 检测其中的像素
for (var i = 0; n = pixels.length, i < n; i += 4) {
var red = pixels[i];
var green = pixels[i+1];
var blue = pixels[i+2];
var alpha = pixels[i+3];
// 检测黑色的墙（如果检测到，说明撞墙了）
if (red == 0 && green == 0 && blue == 0) {
return true;
}
// 检测灰色的边（如果检测到，说明撞墙了）
if (red == 169 && green == 169 && blue == 169) {
return true;
}
}
// 没有撞墙
return false;
}
function drawFrame() {
// 检测笑脸是否正在哪个方向上移动，如果不是，则什么也不做。
if (dx != 0 || dy != 0) {
// 在笑脸当前位置绘制一块黄色背景（表示移动痕迹），然后把笑脸移到下一个位置
context.beginPath();
context.fillStyle = "rgb(254,244,207)";
context.rect(x, y, 15, 15);
context.fill()
// 增大位置值
x += dx;
y += dy;
// 碰撞检测（撞墙的话笑脸需要放回上一个位置并停止移动）
if (checkForCollision()) {
x -= dx;
y -= dy;
dx = 0;
dy = 0;
}
// 这里可以绘制笑脸
var imgFace = document.getElementById("face");
context.drawImage(imgFace, x, y);
// 检测笑脸是否已经到达迷宫底部，是的话提示成功
if (y > (canvas.height - 17)) {
alert("You win!");
return;
}
}
// 10毫秒后绘制下一正
timer = setTimeout(drawFrame, 10);
}
function loadEasy() {
drawMaze('http://www.hangge.com/blog_uploads/201602/2016022313460193716.png', 5, 5);
}
function loadHard() {
drawMaze('http://www.hangge.com/blog_uploads/201602/2016022313455480577.png', 268, 5);
}
</script>
</head>
<body>
<canvas id="canvas">
</canvas>
<div>
<button onclick="loadHard()">加载困难迷宫</button>
<button onclick="loadEasy()">加载简单迷宫</button>
</div>
<img id="face" src="2016022313454739977.png">
</body>
</html>
HTML5 canvas 小游戏练手
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<style type="text/css">
*{padding:0;margin:0;color:#fff;}
a {text-decoration:none;}
html,body{background-color:#000;}
#canvas{background-color:#001022;position:absolute;z-index:-1000;top:0}
#game{margin:auto;width:40%;background-color:#001022;}
#lay{width:100%;height:100%;position:relative}
#game p,h2{text-align:center;width:100%}
#gameInfo{position:relative;margin-top:150px;}
#gameState{margin-top:20px;margin-left:-400px;}
#reset{position:absolute;top:20px;text-decoration:none;margin-left:150px;}
#reset:hover{color:blue}
#play{width:80px;height:40px; font-weight:bold;font-size:25px;margin:10px}
h2{font-size:40px}
#footer{margin-top:120px;display:none}
#play {background: #CCC;color: #333;border-radius: 5px;}
</style>
</head>
<body>
<div id="game">
<p><a href="#" id="reset">Reset</a></p>
<a >太空保龄球</a>
<div id="lay">
<div id="gameUI">
<div id="gameInfo">
<p><h2>Space bowling</h2></p>
<p>This is an awesome game.</p>
<p><button id="play">Play</buttom>
</div>
<div id="gameState">
<p>Asteroids:<label id="bowlNum"></label></p>
<p> Clicks:<label id="ClickNum"></label></p>
</div>
<div id="footer">
<h2>You Win!</h2>
<p>Congratulations,you completed</p>
<p>the game in clicks</p>
<p>Play again</p>
</div>
</div>
</div>
<canvas id="canvas"></canvas>
</div>
</body>
</html>
<script type="text/javascript">
var bowlNum=0;
var clickNum=0;
var viewWidth = 0;
var viewHeight = 0;
try{
viewWidth=document.documentElement.clientWidth;
viewHeight = document.documentElement.clientHeight;
}catch(e){
viewWidth = document.body.clientWidth;
viewHeight = document.body.clientHeight;
}
var canvas = document.getElementById("canvas");
//canvas.width=546
canvas.height=viewHeight;
canvas.width=viewWidth/2.5;
var context = canvas.getContext("2d");
var play = document.getElementById("play");
play.onclick=function(){//开始游戏
document.getElementById("gameInfo").style.display="none";
document.getElementById("footer").style.display="none";
drawBegin();
}
//创建小球类
function bowling(x,y,radius,mass,firction){
this.x = x;
this.y=y;
this.radius = radius;
this.mass = mass;
this.firction=firction;
this.vX=0;
this.vY=0;
this.player=true;
this.R=10;
}
var bowlingArr = new Array();
function drawBegin(){
context.fillStyle="#646464";
context.beginPath();
context.arc(canvas.width/2,160,80,0,2*Math.PI,true);
context.closePath();
context.fill();
context.fillStyle="#fff";
context.beginPath();
context.arc(canvas.width/2,canvas.height-60,10,0,2*Math.PI,true);
var playBowling = new bowling(canvas.width/2,canvas.height-60,0,100,10);
bowlingArr.push(playBowling);
context.closePath();
context.fill();
var radius = 0;
//画若干小球在圆台上
for(var i=0;i<8;i++){
var x=canvas.width/2;
var y=100;
radius=Math.PI/4*(i);
x = Math.floor(x+Math.sin(radius)*60);
y = Math.floor(y+60-Math.cos(radius)*60);
var tempalBowling = new bowling(x,y,10,100,0.95);
tempalBowling.vX=0;
tempalBowling.vY=0;
bowlingArr.push(tempalBowling);
context.beginPath();
context.arc(x,y,10,0,Math.PI*2,true);
context.closePath();
context.fill();
}
var tempalBowling = new bowling(canvas.width/2,160,10,100,0.95);
tempalBowling.vX=0;
tempalBowling.vY=0;
bowlingArr.push(tempalBowling);
context.beginPath();
context.arc(canvas.width/2,160,10,0,Math.PI*2,true);
context.closePath();
context.fill();
radius = 0;
for(var i=0;i<5;i++){
var x=canvas.width/2;
var y=130;
radius=Math.PI*0.4*(i+1);
x = Math.floor(x+Math.sin(radius)*30);
y = Math.floor(y+30-Math.cos(radius)*30);
var tempalBowling = new bowling(x,y,10,100,0.95);
tempalBowling.vX=0;
tempalBowling.vY=0;
bowlingArr.push(tempalBowling);
context.beginPath();
context.arc(x,y,10,0,Math.PI*2,true);
context.closePath();
context.fill();
}
//画一个拖动圆台 描述允许拖动的范围
}
//刷新
function UpdateUI(){
context.clearRect(0,0,canvas.width,canvas.height);
context.fillStyle="#646464";
context.beginPath();
context.arc(canvas.width/2,canvas.height-60,10,0,Math.PI*2,false);
context.closePath();
context.fill();
//圆台
context.fillStyle="#646464";
context.beginPath();
context.arc(canvas.width/2,160,80,0,2*Math.PI,true);
context.closePath();
context.fill();
//15个小球
for(var i=0;i<bowlingArr.length;i++){
if(bowlingArr.player==false)
continue;
context.fillStyle="#ffffff";
context.beginPath();
context.arc(bowlingArr[i].x,bowlingArr[i].y,bowlingArr[i].R,0,Math.PI*2,false);
context.closePath();
context.fill();
if(bowlingArr[i].player==true)
bowlNum++;
}
//更新圆台上小球的数量
document.getElementById("bowlNum").innerHTML=bowlNum;
//更新点击释放小球的次数
document.getElementById("ClickNum").innerHTML = clickNum;
deleteBowling();
}
//删除小球 重置小球
function deleteBowling(){
for(var i=1;i<bowlingArr.length;i++){
if(bowlingArr[i].vX!=0||bowlingArr[i].vY!=0){
var dx=Math.abs(bowlingArr[i].x-canvas.width/2);
var dy=Math.abs(bowlingArr[i].y-160);
var distance = Math.floor(Math.sqrt(dx*dx+dy*dy));
if(distance>80){
bowlingArr[i].R-=0.5;
if(bowlingArr[i].R<=0)
bowlingArr[i].R=0;
bowlingArr[i].player=false;//不将其计入游戏了
}
}
}
//重置拖拽的小球
if(bowlingArr[0].x>canvas.width||bowlingArr[0].y<0||bowlingArr[0].y>canvas.height||bowlingArr[0].y<0){
bowlingArr[0].R=10;
bowlingArr[0].x=canvas.width/2;
bowlingArr[0].y=canvas.height-60;
bowlingArr[0].vX=0;
bowlingArr[0].vY=0;
}
}
//重置游戏
document.getElementById("reset").onclick = function(e){
var evt = e||window.event;
if(!!evt.preventDefualt){
evt.preventDefualt();
}
else{
evt.returnValue=false;
}
document.getElementById("gameInfo").style.display="block";
context.clearRect(0,0,canvas.width,canvas.height);
bowlingArr.length=0;
}
//小球动画
function animate(){
//bowlingArr[0].y-=bowlingArr[0].vy;
for(var i=0;i<bowlingArr.length;i++){
//碰撞检测 方法是两两比较，如果碰撞，能量转化
var tempalA = bowlingArr[i];
for(var j=i+1;j<bowlingArr.length;j++){
var tempalB=bowlingArr[j];
var dx = Math.abs(tempalB.x-tempalA.x);
var dy = Math.abs(tempalB.y-tempalA.y);
var distanceAB = Math.sqrt(dx*dx+dy*dy); //勾股定理
//检测碰撞
if(distanceAB<=tempalA.R+tempalB.R){
//碰了
var angle =Math.atan2(dy,dx);
var sine = Math.sin(angle);
var cosin = Math.cos(angle);
var x=0;
var y=0;
var xB=dx*cosin+dy*sine;
var yB=dy*cosin+dx*sine;
var vy=tempalA.vX*cosin+tempalA.vY*sine;
var vx=tempalA.vY*cosin+tempalA.vX*sine;
var vBX = tempalB.vX*cosin+tempalB.vY*sine;
var vBY = tempalB.vY*cosin+tempalB.vX*sine;
var xTotal = vx-vBX;
vX = ((tempalA.mass-tempalB.mass)*vx+2*tempalB.mass*vBX)/(tempalA.mass+tempalB.mass);
vBX = xTotal+vx;
vY = ((tempalA.mass-tempalB.mass)*vy+2*tempalB.mass*vBY)/(tempalA.mass+tempalB.mass);
vBY = xTotal+vy;
xB = x+(tempalA.radius+tempalB.radius);
tempalA.x = tempalA.x+(x*cosin-y*sine);
tempalA.y = tempalA.y+(y*cosin+x*sine);
tempalB.x = tempalB.x+(xB*cosin-yB*sine);
tempalB.y = tempalB.y+(yB*cosin+yB*sine);
tempalA.vX = vx*cosin - vy*sine;
tempalA.vY = vy*cosin + vx*sine;
tempalB.vX = vBX*cosin - vBY*sine;
tempalB.vY = vBY*cosin + vBY*sine;
}
}
bowlingArr[i].x+=bowlingArr[i].vX;
bowlingArr[i].y+=bowlingArr[i].vY;
}
UpdateUI();
setTimeout(arguments.callee,40);
}
//监听鼠标拖拽，释放小球
var moveAble=false;
var dragable=false;
var clickYN = false;
canvas.onmousedown = function(){
if(bowlingArr[0].y>=canvas.height-60)//必须在这个范围才能拖拽小球
clickYN=true;
}
canvas.onmousemove = function(e){
if(clickYN==true){
dragable=true;
}
if(dragable==true){
//计算拖动角度
bowlingArr[0].x = e.clientX-canvas.offsetLeft;
bowlingArr[0].y = e.clientY-canvas.offsetTop;
bowlingArr[0].vX = -(bowlingArr[0].x-canvas.width/2);
bowlingArr[0].vY = -(bowlingArr[0].y-canvas.height+60);
UpdateUI();
}
}
canvas.onmouseup = function(){
clickYN=false;
if(dragable==true){
clickNum++;//点击次数增加
dragable=false;
moveAble=true;
//开始游戏
if(moveAble)
animate();
}
}
</script>
