Jack Jack - 5 months ago 13
Javascript Question

Javascript timelapse-effect: displaying 30 images/second (read for more detail)

I have a client who has made a 'Visual Diary' of photographs that he took once a day for 365 days, for his portfolio site. He wants me to put these together into a time-lapse effect piece. I thought about using Flash but in the end opted for JavaScript.

What needs to happen is this: The images cycle really really quickly with no transitions or anything, just image-image-image etc. About 30/fps or something like that. When you click the flashing images, it stops on the image you have selected, so the user can take a look. When you click again, the slideshow starts playing again.

My problem is I'm a PHP/XHTML/CSS bloke who hasn't really the foggiest about JavaScript. I can happily integrate it into any page, but it's just coding the JavaScript that's troubling me.

On his homepage, I have this code used to display a basic slideshow - with transition effects etc. It's in the HTML but you can fathom out the code I'm sure:

<!-- Code for slideshow -->
<!-- Found on http://www.webdeveloper.com/forum/showthread.php?t=81441 -->

<SCRIPT LANGUAGE="JavaScript">
<!-- Begin
// Set slideShowSpeed (milliseconds)
var slideShowSpeed = 3000;
// Duration of crossfade (seconds)
var crossFadeDuration = 3;
// Specify the image files
var Pic = new Array();
// to add more images, just continue
// the pattern, adding to the array below

Pic[0] = '1.jpg'
Pic[1] = '2.jpg'
Pic[2] = '3.jpg'
Pic[3] = '4.jpg'
Pic[4] = '5.jpg'
Pic[5] = '6.jpg'
Pic[6] = '7.jpg'
Pic[7] = '8.jpg'
Pic[8] = '9.jpg'
Pic[9] = '10.jpg'
Pic[10] = '11.jpg'
Pic[11] = '12.jpg'
Pic[12] = '13.jpg'
Pic[13] = '14.jpg'
Pic[14] = '15.jpg'
Pic[15] = '16.jpg'
Pic[16] = '17.jpg'
Pic[17] = '18.jpg'
Pic[18] = '19.jpg'
Pic[19] = '20.jpg'

// do not edit anything below this line
var t;
var j = 0;
var p = Pic.length;
var preLoad = new Array();
for (i = 0; i < p; i++) {
preLoad[i] = new Image();
preLoad[i].src = Pic[i];
}
function runSlideShow() {
if (document.all) {
document.images.SlideShow.style.filter="blendTrans(duration=2)";
document.images.SlideShow.style.filter="blendTrans(duration=crossFadeDuration)";
document.images.SlideShow.filters.blendTrans.Apply();
}
document.images.SlideShow.src = preLoad[j].src;
if (document.all) {
document.images.SlideShow.filters.blendTrans.Play();
}
j = j + 1;
if (j > (p - 1)) j = 0;
t = setTimeout('runSlideShow()', slideShowSpeed);
}
// End -->
</script>


Is there any way to modify this code to turn off all transitional effects, and make it stop playing when you click it/start it again? Otherwise, a reference to some different code would be helpful.

Thank you everybody!

Jack

Answer

You seem to be using IE-specific code. I would recommend using the various effects modules in a dedicated JavaScript library such as MooTools (my personal favourite), jQuery, or Prototype + script.aculo.us.

To stop the slideshow, you should be able to simply clear timeout t:

clearTimeout(t);

Also, you shouldn't quote the first parameter of setTimeout. Pass it a function reference:

setTimeout(runSlideShow, slideShowSpeed);
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