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HTML5 canvas （二）

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May 17, 2016 am 09:09 AM

admin html5

绘制图片主要有这三种方式，从下图能很清楚的知道各个参数的作用

drawImage(image,dx,dy)
drawImage(image,sx,sy,sw,sh,dx,dy,dw,dh)
drawImage(image,dx,dy,dw,dh)
其中的 image 参数可以是 HTMLImageElement（img标签的元素）、HTMLCanvasElement （canvas标签的元素）和HTMLVideoElement（video的元素）中的任一个对象。

下面以坦克大战的地图来示意怎么使用，其中资源图片为右图

先上基本结构，上节有讲过

<script></script>
var myCanvas = document.getElementById("myCanvas");
var context = myCanvas.getContext("2d");

然后创建一个图片

var mapImg =new Image();//创建一个图片
mapImg.src = "http://www.w3cfuns.com/data/attachment/forum/201107/26/194717f9ijaam199j9jvkv.png"//坦克地图的图片地址，它的宽为64，高为16。

然后就可以画图了

context.drawImage(mapImg); //在坐标0,0处画图，宽高为图片本身的宽高
context.drawImage(mapImg, 100, 100); //在坐标100, 100处画图，宽高为图片本身的宽高
context.drawImage(mapImg, 100, 200, 640, 233); //在坐标100, 200处画图，宽 640，高 233
context.drawImage(mapImg, 16, 0, 16, 16, 200, 100, 64, 64);//在坐标200,100处画图，宽64，高64，图内容为
距原图左边16，上边0的一个大小为16,16的截图

自己可以试验下[html]

function drawTile(x, y, type)//参数分别为坐标x,y，和地图的类型
function drawTile(x, y, type)
{
context.drawImage(mapImg, type * 16, 0, 16, 16, x, y, 16, 16); //type*16为距原图左边界距离
}

再试着运行下
[html]

var map =var map =
[
[0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0],
[0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0],
[3,3,3,3,0,0,0,0,0,0,1,1,0,0,0,0,0,0,0,0,0,0,0,0,3,3],
[3,3,3,3,0,0,0,0,1,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,3,3],
[3,3,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1,1,0,0,0,0,2,2],
[3,3,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,0,0,0],
[2,2,0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,0,0],
[0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,0,0],
[0,0,0,0,0,1,1,1,0,0,0,0,0,0,1,1,1,1,1,1,0,0,1,0,0,0],
[0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,1,1,1,1,0,0,1,0,0,0],
[4,4,0,0,0,1,0,0,2,0,0,0,2,0,0,0,1,1,1,0,0,0,0,0,0,0],
[4,4,0,0,0,1,0,0,2,0,0,0,2,0,0,0,1,1,1,0,0,0,0,0,0,0],
[0,0,0,0,1,1,0,0,0,0,0,0,0,0,0,0,1,1,1,0,0,0,4,4,4,4],
[0,0,0,0,1,1,0,0,1,1,1,0,0,0,0,1,1,1,1,0,0,0,4,4,4,4],
[0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0],
[0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0],
[0,0,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,0,0,0,0],
[0,0,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,0,0,0,0],
[0,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,0,0,0],
[0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0],
[0,0,1,1,1,1,0,0,1,1,1,1,1,1,1,1,0,0,1,1,1,1,0,0,3,3],
[0,0,1,1,1,1,1,1,0,0,1,1,1,1,0,0,1,1,1,1,1,1,0,0,3,3],
[3,3,0,0,1,1,1,1,0,0,0,0,0,0,0,0,1,1,1,1,0,0,3,3,3,3],
[3,3,0,0,0,0,0,0,0,0,0,1,1,1,1,0,0,0,0,0,0,0,3,3,3,3],
[2,2,3,3,0,0,0,0,0,0,0,1,2,2,1,0,0,0,0,0,3,3,3,3,2,2],
[2,2,3,3,0,0,0,0,0,0,0,1,2,2,1,0,0,0,0,0,3,3,3,3,2,2],
];

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