canvas教程

HTML5-Canvas(3)

字号+ 作者:H5之家 来源:H5之家 2015-11-10 08:12 我要评论( )

lighter darker xor copy 剪切路径 clip () 基本动画 基本的动画步骤: 1.清除canvas clearRect 2.保存canvas状态 save 3.画要做动画的形状 4.恢复canvas状态 如

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引用的内容:[]

var img = new Image();
//User Variables
img.src = 'Capitan_Meadows,_Yosemite_National_Park.jpg';
var CanvasXSize = 800;
var CanvasYSize = 200;
var speed = 30; //lower is faster
var scale = 1.05;
var y = -4.5; //vertical offset
//End User Variables

var dx = 0.75;
var imgW = img.width*scale;
var imgH = img.height*scale;
var x = 0;
if (imgW > CanvasXSize) { x = CanvasXSize-imgW; } // image larger than canvas
var clearX
var clearY
if (imgW > CanvasXSize) { clearX = imgW; } // image larger than canvas
else { clearX = CanvasXSize; }
if (imgH > CanvasYSize) { clearY = imgH; } // image larger than canvas
else { clearY = CanvasYSize; }
var ctx;

function init() {
//Get Canvas Element
ctx = document.getElementById('canvas').getContext('2d');
//Set Refresh Rate
return setInterval(draw, speed);
}

function draw() {
//Clear Canvas
ctx.clearRect(0,0,clearX,clearY);
//If image is <= Canvas Size
if (imgW <= CanvasXSize) {
//reset, start from beginning
if (x > (CanvasXSize)) { x = 0; }
//draw aditional image
if (x > (CanvasXSize-imgW)) { ctx.drawImage(img,x-CanvasXSize+1,y,imgW,imgH); }
}
//If image is > Canvas Size
else {
//reset, start from beginning
if (x > (CanvasXSize)) { x = CanvasXSize-imgW; }
//draw aditional image
if (x > (CanvasXSize-imgW)) { ctx.drawImage(img,x-imgW+1,y,imgW,imgH); }
}
//draw image
ctx.drawImage(img,x,y,imgW,imgH);
//amount to move
x += dx;
}
<body onload="init();">
<canvas id="canvas" width="800" height="200"></canvas>

 

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