Loading CSS background images before normal images? - html

Question

I have a ruby on rails web app, and in some views i have many heavy images( <img> ) to render .The <img> are generated in a Helper.
The problem is that the css is loaded first, then the js, then the heavy images , and then finally the css refereneced background images.
It takes quite a while for all of the heavy images to load, which therefore holds the whole site up.
I want to load first the css background images then load the other images, as they obviously hold visual structure of the page.
rails version: 2.3.8
EDIT:
Thank you guys, I apologize for not having shared the code earlier.
I have two models : Categories and Images, each Category has many images.
In the view i have a list of categories, which is generated by a helper :
categories.each do |cat|
html << "<a href='##{cat.id}' class='mapcat' >#{cat.libelle}</a>"
end
and when I click on the category the images are displayed
categories_images.each do |i|
html << "<div id='#{i.id}' class='#{css}'><img src='/images_moi/categories/#{cat.libelle}/#{i.path_file_name}' />"
end
I have css background image associated to the list of category
The problem is that the images (<img>) is displayed before the css background images of the list of categories.

Answer 1

We need to assume things because you haven't shared your code.
Coming to your query, for now you can preload images using jQuery:
function preload(arrayOfImages) {
$(arrayOfImages).each(function(){
$('<img/>')[0].src = this;
// Alternatively you could use:
// (new Image()).src = this;
});
}
// Usage:
preload([
'img/imageName.jpg',
'img/anotherOne.jpg',
'img/blahblahblah.jpg'
]);
This saves the loading time of loading images.

Answer 2

Use a base64 string.
Example:
background-image: url(data:image/png;base64,*CONVERTED IMAGE DATA HERE*);
without: **
online converter: http://webcodertools.com/imagetobase64converter
note: I only would suggest this if the image size is not too heavy.

Answer 3

Solution: Do not use the img tag.
Create a sprite containing all your images. Load the sprite in your application.html layout once.
Use data uris to transmit the data directly in the html. See http://css-tricks.com/data-uris/

Answer 4

My approach is to lazy load the images using jquery and data- tags. This approach also allows me to choose different images based on device width and spare tablet/mobile users.
<img src="" data-src="/img/graphic-desktop.jpg" data-smallsrc="/img/graphic-smaller.jpg" alt="Graphics" class="lazy" />
<!-- the following would be in your js file -->
$lazy = $('img.lazy');
$(window).load(function(){
// window load will wait for all page elements to load, including css backgrounds
$lazy.each(function(){
// run thru each img.lazy on the page. spare the jquery calls by making $this a variable
$this = $(this);
// if the window is greater then 800px wide, use data-src, otherwise, use the smaller graphic
($(window).width() >= 800) ? $this.attr('src', $this.attr('data-src')) : $this.attr('src', $this.attr('data-smallsrc'));
});
});