http://www.dynamicdrive.com/dynamicindex4/thumbnail.htm

[Tanyati]

1) Script Title: Image Thumbnail Viewer

2) Script URL (on DD): http://www.dynamicdrive.com/dynamicindex4/thumbnail.htm

3) Describe problem: I realise that someone else has queried this but I could not find a resolution. I have the problem on a page with many images that if you click on a thumbnail before all images have downloaded on the page then the image clicked on is displayed in a window over-writing the current page instead of opening up in the image window.

Please can someone help me as to what I can do to prevent this. My affected page is http://www.tanyatiboxers.co.za/a_litter.html

Thanks so much for any help offered!

[jscheuer1]

Use this version of the script I just modified:

// -------------------------------------------------------------------
// Image Thumbnail Viewer Script- By Dynamic Drive, available at: http://www.dynamicdrive.com
// Last updated: January 1st, 2009- eliminate need for onload/onunload events
// -------------------------------------------------------------------

var thumbnailviewer={
enableTitle: true, //Should "title" attribute of link be used as description?
enableAnimation: true, //Enable fading animation?
definefooter: '<div class="footerbar">Click window to Close X</div>', //Define HTML for footer interface
defineLoading: '<img src="loading.gif" /> Loading Image...', //Define HTML for "loading" div

/////////////No need to edit beyond here/////////////////////////

scrollbarwidth: 16,
opacitystring: 'filter:progid:DXImageTransform.Microsoft.alpha(opacity=10); -moz-opacity: 0.1; opacity: 0.1',
targetlinks:[], //Array to hold links with rel="thumbnail"

createthumbBox:function(){
//write out HTML for Image Thumbnail Viewer plus loading div
document.write('<div id="thumbBox" onClick="thumbnailviewer.closeit()"><div id="thumbImage"></div>'+this.definefooter+'</div>')
document.write('<div id="thumbLoading">'+this.defineLoading+'</div>')
this.thumbBox=document.getElementById("thumbBox")
this.thumbImage=document.getElementById("thumbImage") //Reference div that holds the shown image
this.thumbLoading=document.getElementById("thumbLoading") //Reference "loading" div that will be shown while image is fetched
this.standardbody=(document.compatMode=="CSS1Compat")? document.documentElement : document.body //create reference to common "body" across doctypes
},


centerDiv:function(divobj){ //Centers a div element on the page
var ie=document.all && !window.opera
var dom=document.getElementById
var scroll_top=(ie)? this.standardbody.scrollTop : window.pageYOffset
var scroll_left=(ie)? this.standardbody.scrollLeft : window.pageXOffset
var docwidth=(ie)? this.standardbody.clientWidth : window.innerWidth-this.scrollbarwidth
var docheight=(ie)? this.standardbody.clientHeight: window.innerHeight
var docheightcomplete=(this.standardbody.offsetHeight>this.standardbody.scrollHeight)? this.standardbody.offsetHeight : this.standardbody.scrollHeight //Full scroll height of document
var objwidth=divobj.offsetWidth //width of div element
var objheight=divobj.offsetHeight //height of div element
var topposition=(docheight>objheight)? scroll_top+docheight/2-objheight/2+"px" : scroll_top+10+"px" //Vertical position of div element: Either centered, or if element height larger than viewpoint height, 10px from top of viewpoint
divobj.style.left=docwidth/2-objwidth/2+"px" //Center div element horizontally
divobj.style.top=Math.floor(parseInt(topposition))+"px"
divobj.style.visibility="visible"
},

showthumbBox:function(){ //Show ThumbBox div
thumbnailviewer.thumbLoading.style.visibility="hidden" //Hide "loading" div
this.centerDiv(this.thumbBox)
if (this.enableAnimation){ //If fading animation enabled
this.currentopacity=0.1 //Starting opacity value
this.opacitytimer=setInterval("thumbnailviewer.opacityanimation()", 20)
}
},


loadimage:function(link){ //Load image function that gets attached to each link on the page with rel="thumbnail"
if (this.thumbBox.style.visibility=="visible") //if thumbox is visible on the page already
this.closeit() //Hide it first (not doing so causes triggers some positioning bug in Firefox
var imageHTML='<img src="'+link.getAttribute("href")+'" style="'+this.opacitystring+'" />' //Construct HTML for shown image
if (this.enableTitle && link.getAttribute("title")) //Use title attr of the link as description?
imageHTML+='<br />'+link.getAttribute("title")
this.centerDiv(this.thumbLoading) //Center and display "loading" div while we set up the image to be shown
this.thumbImage.innerHTML=imageHTML //Populate thumbImage div with shown image's HTML (while still hidden)
this.featureImage=this.thumbImage.getElementsByTagName("img")[0] //Reference shown image itself
if (this.featureImage.complete)
thumbnailviewer.showthumbBox()
else{
this.featureImage.onload=function(){ //When target image has completely loaded
thumbnailviewer.showthumbBox() //Display "thumbbox" div to the world!
}
}
if (document.all && !window.createPopup) //Target IE5.0 browsers only. Address IE image cache not firing onload bug: panoramio.com/blog/onload-event/
this.featureImage.src=link.getAttribute("href")
this.featureImage.onerror=function(){ //If an error has occurred while loading the image to show
thumbnailviewer.thumbLoading.style.visibility="hidden" //Hide "loading" div, game over
}
},

setimgopacity:function(value){ //Sets the opacity of "thumbimage" div per the passed in value setting (0 to 1 and in between)
var targetobject=this.featureImage
if (targetobject.filters && targetobject.filters[0]){ //IE syntax
if (typeof targetobject.filters[0].opacity=="number") //IE6
targetobject.filters[0].opacity=value*100
else //IE 5.5
targetobject.style.filter="alpha(opacity="+value*100+")"
}
else if (typeof targetobject.style.MozOpacity!="undefined") //Old Mozilla syntax
targetobject.style.MozOpacity=value
else if (typeof targetobject.style.opacity!="undefined") //Standard opacity syntax
targetobject.style.opacity=value
else //Non of the above, stop opacity animation
this.stopanimation()
},

opacityanimation:function(){ //Gradually increase opacity function
this.setimgopacity(this.currentopacity)
this.currentopacity+=0.1
if (this.currentopacity>1)
this.stopanimation()
},

stopanimation:function(){
if (typeof this.opacitytimer!="undefined")
clearInterval(this.opacitytimer)
},


closeit:function(){ //Close "thumbbox" div function
this.stopanimation()
this.thumbBox.style.visibility="hidden"
this.thumbImage.innerHTML=""
this.thumbBox.style.left="-2000px"
this.thumbBox.style.top="-2000px"
},


dotask:function(target, functionref, tasktype){ //assign a function to execute to an event handler (ie: onunload)
var tasktype=(window.addEventListener)? tasktype : "on"+tasktype
if (target.addEventListener)
target.addEventListener(tasktype, functionref, false)
else if (target.attachEvent)
target.attachEvent(tasktype, functionref)
},

init:function(){ //Initialize thumbnail viewer script by scanning page and attaching appropriate function to links with rel="thumbnail"
if (!this.enableAnimation)
this.opacitystring=""
var pagelinks=function(e){
var t;
e = e || window.event;
t = e.target || e.srcElement;
while(t.parentNode && t.nodeName != 'A')
t = t.parentNode;
if (t.nodeName == 'A' && t.rel && t.rel=="thumbnail"){ //Begin if statement
if(e.preventDefault) e.preventDefault();
thumbnailviewer.stopanimation(); //Stop any currently running fade animation on "thumbbox" div before proceeding
thumbnailviewer.loadimage(t); //Load image
return false;
} //end if statement
return undefined;
}
this.dotask(document, pagelinks, 'click');
//Reposition "thumbbox" div when page is resized
this.dotask(window, function(){if (thumbnailviewer.thumbBox.style.visibility=="visible") thumbnailviewer.centerDiv(thumbnailviewer.thumbBox)}, "resize")


} //END init() function

}

thumbnailviewer.createthumbBox() //Output HTML for the image thumbnail viewer
thumbnailviewer.init()

It doesn't require the page to load, it's ready to go as soon as someone can click on a link.

[Tanyati]

Hi John.

I bow in the presence of such greatness!

That seems to work great, no white page with just the image, but it does appear to wait until the entire page has loaded before it displays the image - 'loading image' is displayed while all the images load. Is that correct? This is not a huge problem, and is of course much better than the previous version, so if this is a quirk of the script I can sure live with that.

Thank you SO much for your help!

[jscheuer1]

I didn't think of that, but of course something like that would happen. The browser and the server do a dance whenever they load the page. Items are requested, items are sent, generally they are sent no more than 2 at a time, in the order that they're found, but also in the order requested. When the browser asks for the larger image, if it is still waiting for the results of all of the rest of the page requests, the request for the larger image must wait. The only way to avoid that would be to preload all of the larger images, but that would take so much more time, and in a sense be unnecessary unless the user were going to be viewing everyone.

[Tanyati]

Hi John.

Thanks for the explanation - makes sense to me and I did not know that was how it worked - still learning at the moment.

Thanks again for your help - it looks so much more professional now that a white screen plus image is not displayed.

[jscheuer1]

One other thing that occurred to me is that you can always do anything you can to speed up the loading of the rest of the page. Things like but not limited to (in approximate order of usefulness, varies with different pages):

• Optimize your images.
• Use less images.
• Remove tables, especially nested tables.
• Use less scripts.
• Use less css.
• Remove anything unnecessary, and compress the white space out of all text and code wherever possible without damage.

[Tanyati]

Hi John.

Thanks for this. I'll see what I can do. Images are already optimised and I can't really reduce the number of images due to the nature of the page.

At the end of the day, the fact that the 'loading image' is displayed should keep people waiting as they can see something is happening, albeit rather slowly due to the number of images!