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Its my first time here and I don't know how to indent this sorry :/
I have an image of a van and I am trying to move it across the screen to as if it is driving. Once that is done I will scale the image to appear as if it is moving away (and getting smaller).
I need this to be done in standard javascript without any packages (such as JQuery) please.
What I've got is a van which for a reason I can't break down is moving along 2 paths instead of one. Also moving in the wrong direction (it should move along the path y=-25x so that every 25 pixels moved to the right it should move 1 pixel upwards).
To illustrate what I am trying to achieve, please see this image: http://i.stack.imgur.com/9WIfr.jpg
This is my javascript file:
var viewWidth = 800;
var viewHeight = 480;
var fps = 30;
var delay = getFrame(fps);
var vanWidth, vanHeight, vanObj;
function initVan() {
vanObj = document.getElementById("van");
vanObj.style.position = "absolute";
vanObj.src = "pics/delivery/van.png";
vanWidth = 413;
vanHeight = 241;
var startX = 0-vanWidth;
var startY = viewHeight-vanHeight;
setPosition(startX,startY);
transition(startX,startY,3000);
}
function transition(startX,startY,time) {
//the intention of this is to follow a path y=-25x in mathematical terms
var endX = viewWidth;
var endY = startY-(endX/-25);
//note that this is the velocity per millisecond
var velocityX = (endX-startX)/time;
var velocityY = (endY-startY)/time;
alert(endY+", "+startY);
move(velocityX,velocityY,endX,endY);
}
function move(vX,vY,eX,eY) {
var posX = getX();
var posY = getY();
if (posX<=eX || posY<=eY) {
//velocityX (in milliseconds) * delay = the amount of pixels moved in one frame @fps=30
var moveX = vX*delay;
var moveY = vY*delay;
var newX = posX+moveX;
var newY = posY+moveY;
setPosition(newX,newY);
setTimeout(function() {
move(vX,vY,eX,eY);
}, delay);
}
}
function getX() {
return vanObj.offsetLeft;
}
function getY() {
return vanObj.offsetTop;
}
function setPosition(newX,newY) {
vanObj.style.left = newY + "px";
vanObj.style.top = newX + "px";
}
function setSize(scaleX,scaleY) {
vanWidth *= scaleX;
vanHeight *= scaleY;
vanObj.width = vanWidth;
vanObj.height = vanHeight;
}
function getFrame(fps) {
return Math.floor(1000/fps);
}
This is my HTML file:
<script type="text/javascript" src="delivery.js"> </script>
<body onLoad="initVan();">
<img id="van" width=413 height=241/>
880
Unless you have a no-libraries requirement, or particularly enjoy reinventing the wheel, I'd solve this using jQuery's effects library, and in particular .animate: http://api.jquery.com/animate/. See the first example on that page.
$(document).ready(function() {
$('#van')
.attr({
width: 413,
height: 241 //etc.
})
.animate({
width: "70%",
height: "70%" //etc.
}, 3000);
});
Less code means less maintenance. Means happy customer.
71
Even though you already accepted an answer, heres a way to do it without jQuery.
Not finished, but the concept works.
window.onload = function () {
updateVan(0);
function updateVan(i)
{
var t = setTimeout(function () {
document.getElementById("van").style.marginLeft = i + "px";
document.getElementById("van").style.marginTop = (i/10) + "px";
document.getElementById("van").style.height = (100-(i/10)) + "px";
document.getElementById("van").style.width = (100-(i/10)) + "px";
if (i < 300) updateVan(i+1);
},30);
}
}
Working demo here: http://webbies.dk/tmp/tmp.html
2
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