I have this code here where I have a slider with thumbnails and the sliders large image takes it's next attr('src') from the click on a thumb, but I'd like to change that src only when the image has loaded. This is the source that I've come up with so far:
$('.thumb').click(function(){
topImageSrc = $(this).data("bigimage");
$(topImageSrc).load(function(){
coverMain.attr('src',topImageSrc);
main.fadeOut("slow");
})
});
Sadly this doesn't work as the topImageSrc is just a path variable to the large image, like so: /uploads/largeimages/pic1.jpg
How could I force it to load and then check if it's done, after that - apply the new image?
You can do it like this:
$('.thumb').click(function () {
topImageSrc = $(this).data("bigimage");
var topImage = $('<img>').attr('src', topImageSrc);
$(topImage).load(function () {
coverMain.attr('src', topImageSrc);
main.fadeOut("slow");
});
});
This creates an image (without appending it anywhere), sets its source to the topImageSrc URL and checks for the load event.
I have a page that swaps some fairly large images in and out. There are too many to preload when the page initially loads so that is not an option. So what I need to do is load them as they are requested by the user. Right now I'm using jQuery to replace the img's src. This works fine but the images I am loading can be around 500KB and it looks bad as they paint down the screen as they are downloading. What I'd like to do is pop a loading gif on the page when the image is in the process of loading then have the loading gif disappear once the image is loaded. I'm struggling to find a way to do that though. Here is the JS/jQuery code that I have that just replaces the src.
var product = "bowl";
var image = "dog.jpg"; //this is actually pulled from a data attribute, but its just hardcoded here for an example
$("#images img[data-product="+product+"]").attr("src", "/img/tablesetting/"+image);
I made a working jsfiddle showing this principle
http://jsfiddle.net/kasperfish/c72RT/4/
I recently needed to do the same thing. Basically I wrapped the image in a container div. within the container I've added a span element with my ajax loader gif embedded. this span has to be hidden initially but gets visible when an ajax request is made. The span gets removed when the image is fully loaded.
before ajax call
$('#your_image_container').find('span').show();
on success
$('#your_image').attr('src', 'your/image/url').load(function() {
$('#your_image_container').find('span').fadeOut();
});
I made a jsfiddle showing this principle
http://jsfiddle.net/kasperfish/c72RT/4/
Preload the image.
var product = "bowl";
var imageSrc = "dog.jpg";
var imgEl = $("#images img[data-product="+product+"]");
// show loading graphic only if it's needed
var timer = setTimeout(function(){
imgEl.attr("src", "/img/loading.gif");
},50);
// preload image
var img = new Image();
img.onload = function() {
clearTimeout(timer);
imgEl.attr("src",imageSrc);
}
img.src = imageSrc;
$img.attr("src", newImage);
if (!$img.get(0).complete) {
$img
.hide()
.after("<img src=throbber>")
.on("load", function () {
$(this).show().next().remove();
});
}
I'm currently working on a web application which has a page which displays a single chart (a .png image). On another part of this page there are a set of links which, when clicked, the entire page reloads and looks exactly the same as before except for the chart in the middle of the page.
What I want to do is when a link is clicked on a page just the chart on the page is changed. This will speed things up tremendously as the page is roughly 100kb large, and don't really want to reload the entire page just to display this.
I've been doing this via JavaScript, which works so far, using the following code
document.getElementById('chart').src = '/charts/10.png';
The problem is that when the user clicks on the link, it may take a couple of seconds before the chart changes. This makes the user think that their click hasn't done anything, or that the system is slow to respond.
What I want to happen is display a spinner / throbber / status indicator, in place of where the image is while it is loading, so when the user clicks the link they know at least the system has taken their input and is doing something about it.
I've tried a few suggestions, even using a psudo time out to show a spinner, and then flick back to the image.
A good suggestion I've had is to use the following
<img src="/charts/10.png" lowsrc="/spinner.gif"/>
Which would be ideal, except the spinner is significantly smaller than the chart which is being displayed.
Any other ideas?
I've used something like this to preload an image and then automatically call back to my javascript when the image is finished loading. You want to check complete before you setup the callback because the image may already be cached and it may not call your callback.
function PreloadImage(imgSrc, callback){
var objImagePreloader = new Image();
objImagePreloader.src = imgSrc;
if(objImagePreloader.complete){
callback();
objImagePreloader.onload=function(){};
}
else{
objImagePreloader.onload = function() {
callback();
// clear onLoad, IE behaves irratically with animated gifs otherwise
objImagePreloader.onload=function(){};
}
}
}
You could show a static image that gives the optical illusion of a spinny-wheel, like these.
Using the load() method of jQuery, it is easily possible to do something as soon as an image is loaded:
$('img.example').load(function() {
$('#spinner').fadeOut();
});
See: http://api.jquery.com/load-event/
Use the power of the setTimeout() function (More info) - this allows you set a timer to trigger a function call in the future, and calling it won't block execution of the current / other functions (async.).
Position a div containing the spinner above the chart image, with it's css display attribute set to none:
<div> <img src="spinner.gif" id="spinnerImg" style="display: none;" /></div>
The nbsp stop the div collapsing when the spinner is hidden. Without it, when you toggle display of the spinner, your layout will "twitch"
function chartOnClick() {
//How long to show the spinner for in ms (eg 3 seconds)
var spinnerShowTime = 3000
//Show the spinner
document.getElementById('spinnerImg').style.display = "";
//Change the chart src
document.getElementById('chart').src = '/charts/10.png';
//Set the timeout on the spinner
setTimeout("hideSpinner()", spinnerShowTime);
}
function hideSpinner() {
document.getElementById('spinnerImg').style.display = "none";
}
Use CSS to set the loading animation as a centered background-image for the image's container.
Then when loading the new large image, first set the src to a preloaded transparent 1 pixel gif.
e.g.
document.getElementById('mainimg').src = '/images/1pix.gif';
document.getElementById('mainimg').src = '/images/large_image.jpg';
While the large_image.jpg is loading, the background will show through the 1pix transparent gif.
Building on Ed's answer, I would prefer to see something like:
function PreLoadImage( srcURL, callback, errorCallback ) {
var thePic = new Image();
thePic.onload = function() {
callback();
thePic.onload = function(){};
}
thePic.onerror = function() {
errorCallback();
}
thePic.src = srcURL;
}
Your callback can display the image in its proper place and dispose/hide of a spinner, and the errorCallback prevents your page from "beachballing". All event driven, no timers or polling, plus you don't have to add the additional if statements to check if the image completed loading while you where setting up your events - since they're set up beforehand they'll trigger regardless of how quickly the images loads.
Some time ago I have written a jQuery plugin which handles displaying a spinner automatically http://denysonique.github.com/imgPreload/
Looking in to its source code should help you with detecting when to display the spinner and with displaying it in the centre of the loaded image.
I like #duddle's jquery method but find that load() isn't always called (such as when the image is retrieved from cache in IE). I use this version instead:
$('img.example').one('load', function() {
$('#spinner').remove();
}).each(function() {
if(this.complete) {
$(this).trigger('load');
}
});
This calls load at most one time and immediately if it's already completed loading.
put the spinner in a div the same size as the chart, you know the height and width so you can use relative positioning to center it correctly.
Aside from the lowsrc option, I've also used a background-image on the img's container.
Be aware that the callback function is also called if the image src doesn't exist (http 404 error). To avoid this you can check the width of the image, like:
if(this.width == 0) return false;
#iAn's solution looks good to me. The only thing I'd change is instead of using setTimeout, I'd try and hook into the images 'Load' event. This way, if the image takes longer than 3 seconds to download, you'll still get the spinner.
On the other hand, if it takes less time to download, you'll get the spinner for less than 3 seconds.
I would add some random digits to avoid the browser cache.
Title is self-explanatory, but I'll provide a step-by-step view on the matter. Hopefully I'm not the first one to have noticed this (apparently) bug on Webkit/Chrome.
I want to reset a GIF animation. All of the examples I've seen so far either simply set the src of the image to itself or set it to an empty string followed by the original src again.
Take a look at this JSFiddle for reference. The GIF resets perfectly fine on IE, Firefox and Chrome.
The issue which I have is when the image has display:none on Google Chrome only.
Check this JSFiddle. The GIF resets fine on IE and Firefox before being displayed in the page, but Chrome simply refuses to reset its animation!
What I've tried so far:
Setting the src to itself as in Fiddle, doesn't work in Chrome.
Setting the src to an empty string and restoring it to the default, doesn't work either.
Putting an wrapper around the image, emptying the container through .html('') and putting the image back inside of it, doesn't work either.
Changing the display of the image through .show() or .fadeIn() right before setting the src doesn't work either.
The only workaround which I've found so far is keeping the image with its default display and manipulating it through .animate()ing and .css()ing the opacity, height and visibility when necessary to simulate a display:none behaviour.
The main reason (context) of this question is that I wanted to reset an ajax loader GIF right before fading it in the page.
So my question is, is there a proper way to reset a GIF image's animation (which avoids Chrome's display:none "bug") or is it actually a bug?
(ps. You may change the GIF in the fiddles for a more appropriate/longer animation gif for testing)
The most reliable way to "reset" a GIF is by appending a random query string. However this does mean that the GIF will be redownloaded every time so make sure it's a small file.
// reset a gif:
img.src = img.src.replace(/\?.*$/,"")+"?x="+Math.random();
Chrome deals with style changes differently than other browsers.
In Chrome, when you call .show() with no argument, the element is not actually shown immediately right where you call it. Instead, Chrome queues the application of the new style for execution after evaluating the current chunk of JavaScript; whereas other browsers would apply the new style change immediately. .attr(), however, does not get queued. So you are effectively trying to set the src when the element is still not visible according to Chrome, and Chrome won't do anything about it when the original src and new src are the same.
Instead, what you need to do is to make sure jQuery sets the src after display:block is applied. You can make use of setTimeout to achieve this effect:
var src = 'http://i.imgur.com/JfkmXjG.gif';
$(document).ready(function(){
var $img = $('img');
$('#target').toggle(
function(){
var timeout = 0; // no delay
$img.show();
setTimeout(function() {
$img.attr('src', src);
}, timeout);
},
function(){
$img.hide();
}
);
});
This ensures that src is set after display:block has been applied to the element.
The reason this works is because setTimeout queues the function for execution later (however long later is), so the function is no longer considered to be part of the current "chunk" of JavaScript, and it provides a gap for Chrome to render and apply the display:block first, thus making the element visible before its src attribute is set.
Demo: http://jsfiddle.net/F8Q44/19/
Thanks to shoky in #jquery of freenode IRC for providing a simpler answer.
Alternatively, you can force a redraw to flush the batched style changes. This can be done, for example, by accessing the element's offsetHeight property:
$('img').show().each(function() {
this.offsetHeight;
}).prop('src', 'image src');
Demo: http://jsfiddle.net/F8Q44/266/
Just because I still need this every now and then I figured the pure JS function I use might be helpful for someone else. This is a pure JS way of restarting an animated gif, without reloading it. You can call this from a link and/or document load event.
<img id="img3" src="../_Images/animated.gif">
<a onClick="resetGif('img3')">reset gif3</a>
<script type="text/javascript">
// reset an animated gif to start at first image without reloading it from server.
// Note: if you have the same image on the page more than ones, they all reset.
function resetGif(id) {
var img = document.getElementById(id);
var imageUrl = img.src;
img.src = "";
img.src = imageUrl;
};
</script>
On some browsers you only need to reset the img.src to itself and it works fine. On IE you need to clear it before resetting it. This resetGif() picks the image name from the image id. This is handy in case you ever change the actual image link for a given id because you do not have to remember to change the resetGiF() calls.
--Nico
This solution preloads the gif and takes it out of the dom and then back in the src (thus avoiding another download)
I just tested it using jquery to remove the attribute and it works fine.
Example:
<html>
<head>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js" type="text/javascript"></script>
<script>
$(function() {
$('.reset').click(resetGif);
function resetGif()
{
$('.img1').removeAttr('src', '');
}
});
</script>
</head>
<body>
<img class="img1" src="1.gif" />
reset gif
</body>
</html>
This seemed to work for me in Chrome, it runs each time just before I fade in the image and clears then refills the src and my animation now starts from the beginning every time.
var imgsrc = $('#my_image').attr('src');
$('#my_image').attr('src', '');
$('#my_image').attr('src', imgsrc);
I've a button with the an animated no-loop image in it. I just reload the image with some jquery and this seems to be working for me.
var asdf = $(".settings-button img").attr("src");
$(".settings-button img").attr("src", "").attr("src", asdf);
here's my hack for background images:
$(document).on('mouseenter', '.logo', function() {
window.logo = (window.logocount || 0) + 1;
var img = new Image();
var url = "/img/mylogimagename.gif?v=" + window.logocount;
var that = this;
$(img).load(function(){
$(that ).css('background-image','url(' + url + ')');
});
img.src = url;
});
I experienced problems with all of the above solutions. What finally worked was replacing the src temporarily with a transparent 1px gif:
var transparent1PxGif = 'data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7';
var reloadGif = function(img) {
var src = img.src;
img.src = transparent1PxGif;
img.offsetHeight; // triggers browser redraw
img.src = src;
};
It's been several years and I've decided to revisit this since we have a number of new options at our disposal.
The issue with my previous answer is that it forces a re-download of the GIF every single time you want to re-start it. While that's fine for small files, it's still an overhead that's best avoided if possible.
With that in mind, I've got a new solution that uses AJAX to download the GIF once, and then converts it into a data URL (via a FileReader) and uses that as the source with a random query string attached.
This way, the browser only ever downloads the image once, and can even cache it properly, and the "reset" pulls from that pre-downloaded resource.
The only catch, of course, is that you have to make sure it's properly loaded before you can use it.
Demo: http://adamhaskell.net/misc/numbers/numbers.html
Relevant code:
var url = "something.gif"; // fallback until the FileReader is done
function setup() {
var xhr = new XMLHttpRequest();
xhr.open("GET",url,true);
xhr.responseType = "blob";
xhr.onreadystatechange = function() {
if( this.readyState == 4) {
var fr = new FileReader();
fr.onload = function() {
url = this.result; // overwrite URL with the data one
};
fr.readAsDataURL(this.response);
}
};
xhr.send();
}
function getGIF() {
return url+"?x="+Math.random();
}
Reset gif animation
When the browser render img, the source specified in src attribute is cached into memory for future reuse. This allows to increase the speed of page loading/reloading, as well as reduce the load on the network. And this behavior suits mostly everyone, because in reality, this is the most optimal and demanded option.
However, as always, there are exceptions. I came up with a dataUrl-based animation update option that solves several problems.
Issues solved:
Need to display gif images with animation without a loop (loop = 1), which may have the same src. But when one such picture appears, it is necessary that it play the animation without changing the animation of other pictures with the same src. The same picture should be loaded from server only once. Stackoverflow
Reset gif animation.
Start animation on hover
Reset src attribute
If we use a solution that clears the src attribute of an image, then all images with the same source will replay their animation. Unfortunately, I still did not fully understand why this is happening, but it interferes with correct work.
Cons
Reset animation of all images with the same src.
There are problems in mobile devices
Pros
Easy and fast
Modify url with random query
This solution consists in adding a random query parameter to the end of the src attribute, so that all images will have a different source, and therefore they will animate independently of each other. There is one big fat NO: this will lead to a constant request to the server to download the picture, and therefore they will no longer be cached. And if we need to display 100 identical pictures, then there will be 100 requests to the server. Rough and tough, but it always works.
Cons
Each picture with a unique query will be reloaded from the server.
Pros
Easy and fast
Modify dataUrl (Proposed Solution)
Data URLs, URLs prefixed with the data: scheme, allow content creators to embed small files inline in documents. They were formerly known as "data URIs" until that name was retired by the WHATWG.
MDN
The dataUrl structure from this documentation:
data:[<mediatype>][;base64],<data>
And this is how it is indicated in the specification:
dataurl := "data:" [ mediatype ] [ ";base64" ] "," data
mediatype := [ type "/" subtype ] *( ";" parameter )
data := *urlchar
parameter := attribute "=" value
If you look closely at the description of mediatype, then some strange parameter is indicated there. But, there is also a specification:
attribute := token
; Matching of attributes
; is ALWAYS case-insensitive.
value := token / quoted-string
token := 1*<any (US-ASCII) CHAR except SPACE, CTLs, or tspecials>
tspecials := "(" / ")" / "<" / ">" / "#" /
"," / ";" / ":" / "\" / <">
"/" / "[" / "]" / "?" / "="
; Must be in quoted-string,
; to use within parameter values
As can be seen, we can specify any parameter, the main thing is that it meets the requirements presented above!
Therefore, we can embed an additional attribute in the mediatype, which will not affect the image in any way, but the data url will differ from the same image.
Generalized algorithm:
We load the image through a regular request and remove the metadata from created dataUrl from blob.
fetch("https://cdn140.picsart.com/330970106009201.gif").then(async (res) => {
const blob = await res.blob();
const reader = new FileReader();
reader.onload = (ev) => {
// It would be reasonable to remove metadata to the point!
// But for simplicity, I'm using this implementation.
const dataUrl = ev.currentTarget.result.replace(
"data:image/gif;base64",
""
);
};
reader.readAsDataURL(blob);
});
Create/edit img element with src attribute "src=data:image/gif;base64;${Math.random()}${dataUrl}"
That is all!
Example Vanila JS
const url = "https://cdn140.picsart.com/330970106009201.gif";
function loadImage(src) {
fetch(src)
.then((res) => res.blob())
.then(async(blob) => {
const reader = new FileReader();
reader.onload = (ev) => {
const dataUrl = ev.currentTarget.result.replace("data:image/gif;base64", "")
const container = document.getElementById("container");
while (container.firstChild) {
container.firstChild.remove()
}
for (let i = 0; i < 6; i++) {
const img = document.createElement("img");
img.setAttribute("src", `data:image/gif;base64;gif-id=${Date.now()}${dataUrl}`)
container.appendChild(img);
img.addEventListener('click', ev => {
img.setAttribute("src", `data:image/gif;base64;gif-id=${Date.now()}${dataUrl}`)
})
}
};
reader.readAsDataURL(blob);
});
}
loadImage(url);
function updateImage() {
const newSrc = document.getElementById("image-src");
loadImage(document.getElementById("image-src").value);
}
#main {
display: flex;
flex-direction: column;
gap: 5px;
}
img {
width: 128px;
height: 128px;
padding: 5px;
}
<div id="main">
<label>Change gif url if current will become unavailable </label>
<input id="image-src" value="https://cdn140.picsart.com/330970106009201.gif"></input>
<button onclick="updateImage()">Update image source attribute</button>
<span>Click to reset!</span>
<div id="container">
</div>
</div>
Example React
import React, { useState, useRef } from "react";
function App() {
const [stars, setStars] = useState(0);
const [data, setData] = useState(null);
const ref = useRef(null);
React.useEffect(() => {
fetch("https://cdn140.picsart.com/330970106009201.gif")
.then((res) => res.blob())
.then(async (text) => {
const reader = new FileReader();
reader.onload = (ev) => {
setData(ev.currentTarget.result.replace("data:image/gif;base64", ""));
};
reader.readAsDataURL(text);
});
}, []);
return (
<React.Fragment>
<p onClick={() => setStars((s) => s + 1)}>+</p>
{data &&
new Array(stars).fill().map((s, ind) => {
return <Star src={data} key={ind}></Star>;
})}
<p onClick={() => setStars((s) => (s === 0 ? 0 : s - 1))}>-</p>
</React.Fragment>
);
}
export function Star(props) {
const [id] = useState(Math.random());
return (
<img
className="icon"
src={`data:image/gif;base64;gif-id=${id}` + props.src}
alt="animated star"
/>
);
}
export default App;
I came across this thread after searching many others. David Bell's post led me to the solution I needed.
I thought I'd post my experience in the event that it could be useful for anyone trying to accomplish what I was after. This is for an HTML5/JavaScript/jQuery web app that will be an iPhone app via PhoneGap. Testing in Chrome.
The Goal:
When user taps/clicks button A, an animated gif appears and plays.
When user taps/clicks button B, gif disappears.
When user taps/clicks button A again, after tapping/clicking button
B, animated gif should reappear and play from the beginning.
The Problem:
On tap/click of button A, I was appending the gif to an existing div. It would play fine.
Then, on tap/click of button B, I was hiding the container div, then setting the img src of the gif to an empty string (''). Again, no problem (that is, the problem wasn't evident yet.)
Then, on tap/click of button A, after tap/click of button B, I was re-adding the path to the gif as the src.
- This did not work. The gif would show up on subsequent taps/clicks of button A...however, the more I tapped/clicked button A, the more times the gif would load and start over. That is, if I went back and forth, tapping/clicking button A then button B 3 times, the gif would appear and then start/stop/start 3 times...and my whole app started to chug. I guess the gif was being loaded multiple times, even though I had set the src to an empty string when button B was tapped/clicked.
The Solution:
After looking at David Bell's post, I arrived at my answer.
I defined a global variable (let's call it myVar) that held the container div and the image (with the source path) within.
On the tap/click function of button A, I appended that container div to an existing parent div in the dom.
In that function, I created a new variable that holds the src path of the gif.
Just like David suggested, I did this (plus an append):
$('#mainParent').append(myVar);
var imgsrc = $('#my_image').attr('src');
$('#my_image').attr('src', '');
$('#my_image').attr('src', imgsrc);
THEN, in the function for button B, I set the src to an empty string and then removed the div containing the gif:
$('#my_image').attr('src', '');
$('#mainParent').find('#my_image').remove();
Now, I can tap/click button A then button B then button A, etc., all day long. The gif loads and plays on tap/click of button A, then hides on tap/click of button B, then loads and plays from the beginning on subsequent taps of button A every time with no issues.
I worked out a complete solution for this problem. It can be found here: https://stackoverflow.com/a/31093916/1520422
My solution restarts the animation WITHOUT re-loading the image data from the network.
It also enforces the image to repaint to fix some painting artefacts that occured (in chrome).
I'm building a Javascript lightbox and I'm trying to adjust the size once the image has loaded. I'm using the code below, which works fine - it outputs the correct width once loaded.
My problem:
When I refresh, it will load the image instantly from the cache, and it seems to bypass the load. I get an instant zero for the width. Why does this happen?
My code:
var oImage = new Image();
oImage.src = 'http://mydomain.com/image.png';
container.html(oImage);
oImage.onload = function(){
alert(this.width);
}
** Update **
#Alex: This is the code I've tried with your plugin, I assume I'm probably doing something wrong. I'd be eager to get this working because your plugin looks quite good.
container.waitForImages(function() {
var cWidth = $(this).width();
alert("width: "+cWidth); // returns 0 - works first time but not cached
});
// Adding the image to the container for preload
container.html('<img src="mygraphic.png" />');
You need to do a few things...
Check the complete property of the img element.
Attach the load event before setting the src property.
Also, I found creating a new Image and assigning the src there is the best way to determine if the image has loaded or not.
You may want to switch the .html() and the .onload() calls.
If the image is loading from cache, I'm imagining that the .html() call completes before the script has had a chance to attach a function handler to the image's onload event. Therefore, effectively bypassing the load event itself (as the image has already loaded).
If it's still downloading the image (i.e. not cached), there will be more than enough time to call the .onload attach before the image completely finishes rendering.
While you're at it, you may want to do this the jQuery way, just so you're attaching events more similarly to DOM2 than DOM0.
var image = $('<img/>', {
src : 'http://mydomain.com/image.png'
}).load(function () {
alert(this.width);
})
// maybe clear container before if you want
.appendTo(container);
If we're going to have to set the src after the onload, we might as well do this instead:
var image = $('<img/>')
.load(function () {
alert(this.width);
})
.attr('src','http://mydomain.com/image.png')
.appendTo(container)
;
Hopefully that works cleanly.
This answer JavaScript: Know when an image is fully loaded suggests that you should set onload before setting src