我試圖在畫布環境中淡入淡出圖像。 Essientially我想要做的是從左到右移動一個圖像,我想淡化它從0%alpha到100%alpha。當我在我的代碼中註釋globalAlpha和alpha信息時,它會像我想要的那樣移動,我唯一的問題是讓它淡出。我能夠使globalAlpha函數起作用,但它會影響畫布區域中的所有作品。有什麼辦法可以影響一個元素?最終我會想要在基於計時器的動畫中的不同時間淡入多個元素,但是如果我可以先讓它工作,我可以從那裏開始。淡入淡出
window.addEventListener('load', eventWindowLoaded, false);
function eventWindowLoaded()
{
canvasApp();
}
function canvasSupport()
{
return Modernizr.canvas;
}
function canvasApp()
{
if (!canvasSupport())
{
return;
}
var pointImage = new Image();
pointImage.src = "images/barry.png";
var barry = new Image();
barry.src = "images/barry.png";
/*var alpha = 0;
context.globalAlpha = 1;*/
function drawScreen()
{
//context.globalAlpha = 1;
context.fillStyle = '#EEEEEE';
context.fillRect(0, 0, theCanvas.width, theCanvas.height);
//context.globalAlpha = alpha;
//Box
context.strokeStyle = '#000000';
context.strokeRect(1, 1, theCanvas.width-2, theCanvas.height-2);
if (moves > 0)
{
moves--;
ball.x += xunits;
ball.y += yunits;
}
context.drawImage(barry, ball.x, ball.y);
/*context.restore();
alpha += .1;
if (alpha > 1)
{
alpha = 0;
}*/
}
var speed = 1;
var p1 = {x:20,y:250};
var p2 = {x:40,y:250};
var dx = p2.x - p1.x;
var dy = p2.y - p1.y;
var distance = Math.sqrt(dx*dx + dy*dy);
var moves = distance/speed;
var xunits = (p2.x - p1.x)/moves;
var yunits = (p2.y - p1.y)/moves;
var ball = {x:p1.x, y:p1.y};
var points = new Array();
theCanvas = document.getElementById("canvas");
context = theCanvas.getContext("2d");
ctx = theCanvas.getContext("2d");
setInterval(drawScreen, 10);
}
歡迎任何建議!
特別是你不使用jQuery的原因嗎? – Cameron 2012-04-02 00:20:13
你可以設置上下文到一個區域,然後修改alpha? – alex 2012-04-02 00:26:05
知道jQuery是要走的路,爲了學習的目的而進行猜測我試圖從編碼的立場上學到儘可能多的東西,但我可以......但jQuery絕對是在地平線上。 – user1075004 2012-04-02 03:54:28