[英]Random images falling like rain in canvas (Javascript)
所以我一直在玩帆布。 試圖模擬隨機落下的物體,繪制背景圖像是沒有問題的,而不是應該模擬雨滴的第二個img。
我可以得到隨機x下降,但現在我不確定如何循環下降圖像x次由變量noOfDrops設置。
我把循環注釋掉了,只有一滴掉落的工作代碼是:
<!DOCTYPE html>
<html lang="en">
<head>
<title>Canvas Regn</title>
<script type="text/javascript">
var ctx;
var imgBg;
var imgDrops;
var x = 0;
var y = 0;
var noOfDrops = 50;
var fallingDrops = [];
function setup() {
var canvas = document.getElementById('canvasRegn');
if (canvas.getContext) {
ctx = canvas.getContext('2d');
setInterval('draw();', 36);
imgBg = new Image();
imgBg.src = 'dimma.jpg';
imgDrops = new Image();
imgDrops.src = 'drop.png';
/*for (var i = 0; i < noOfDrops; i++) {
var fallingDr = imgDrops[i];
fallingDr.x = Math.random() * 600;
fallingDrops.push(fallingDr);
}*/
}
}
function draw() {
drawBackground();
ctx.drawImage (imgDrops, x, y); //The rain drop
y += 3; //Set the falling speed
if (y > 450) { //Repeat the raindrop when it falls out of view
y = -25 //Account for the image size
x = Math.random() * 600; //Make it appear randomly along the width
}
}
function drawBackground(){
ctx.drawImage(imgBg, 0, 0); //Background
}
</script>
</head>
<body onload="setup();">
<canvas id="canvasRegn" width="600" height="450"style="margin:100px;"></canvas>
</body>
</html>
如果有人對如何實現它有一些好的想法,我會很感激。
你的循環實際上非常接近。 你可能遇到的最大問題是你不能只保持1 x和1 y的值,你必須保持每個圖像。 所以我稍微修改了你的循環以推送具有x,y和speed值的數組上的對象。 速度值為您提供了良好的運動隨機化,因此一切都不會以相同的速度降低:
var ctx;
var imgBg;
var imgDrops;
var x = 0;
var y = 0;
var noOfDrops = 50;
var fallingDrops = [];
function drawBackground(){
ctx.drawImage(imgBg, 0, 0); //Background
}
function draw() {
drawBackground();
for (var i=0; i< noOfDrops; i++)
{
ctx.drawImage (fallingDrops[i].image, fallingDrops[i].x, fallingDrops[i].y); //The rain drop
fallingDrops[i].y += fallingDrops[i].speed; //Set the falling speed
if (fallingDrops[i].y > 450) { //Repeat the raindrop when it falls out of view
fallingDrops[i].y = -25 //Account for the image size
fallingDrops[i].x = Math.random() * 600; //Make it appear randomly along the width
}
}
}
function setup() {
var canvas = document.getElementById('canvasRegn');
if (canvas.getContext) {
ctx = canvas.getContext('2d');
imgBg = new Image();
imgBg.src = "http://lorempixel.com/600/600/sports/";
setInterval(draw, 36);
for (var i = 0; i < noOfDrops; i++) {
var fallingDr = new Object();
fallingDr["image"] = new Image();
fallingDr.image.src = 'http://lorempixel.com/10/10/sports/';
fallingDr["x"] = Math.random() * 600;
fallingDr["y"] = Math.random() * 5;
fallingDr["speed"] = 3 + Math.random() * 5;
fallingDrops.push(fallingDr);
}
}
}
setup();
這是一個小提琴演示: http : //jsfiddle.net/L4Qfb/21/
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