Css – Background image fixed and cover on mobile / tablet

cssresponsive-designsmartphonetablet

How do you get a fixed background image that scales to viewport to work correctly on smartphone / tablet?

Any of the methods mentioned here do not work well with what I've tested (Galaxy Nexus & TF300t, using default browser, Firefox, or Chrome all have trouble with flashing / strange resizing, or ignoring the "cover" instruction)

The one thing I've come to see is to not put the background image on the HTML tag for touch devices, because they seems to scroll a full height viewport rather than scroll within the HTML tag.

body {
  background: black url("../img/cover.jpg") no-repeat top center fixed;
  -webkit-background-size: cover; 
  -moz-background-size: cover; 
  -o-background-size: cover; 
  background-size: cover;
}

Best Answer

I've written some months ago an approach what fits your needs: http://plugins.jquery.com/fitpic/

HTML

<img src="http://ge.tt/api/1/files/1jN8IzR/0/blob?download" class='bg'>

CSS not really needed

.bg {
    position: fixed;
    top: 0;
    left: 0;
    z-index: -1
}

var fitPic = (function() {
    var winW = $(window).width(),
        winH = window.innerHeight || $(window).height(); // `innerHeight` for mobile safari

    $(".bg").each(function() {

        var elem = $(this),
            elemW = elem.width(),
            elemH = elem.height(),

            imgW = (elemW * winH) / elemH,
            imgH = (elemH * winW) / elemW,

            newW = imgH < winH ? imgW : winW,
            newH = imgH < winH ? winH : imgH;

        this.style.width = newW + "px";
        this.style.height = newH + "px";

    });
});

$(window).on('load resize', fitPic);

Related Solutions

Css – Hide text using css

This is one way:

h1 {
    text-indent: -9999px;                 /* sends the text off-screen */
    background-image: url(/the_img.png);  /* shows image */
    height: 100px;                        /* be sure to set height & width */
    width: 600px;
    white-space: nowrap;            /* because only the first line is indented */
}

h1 a {
    outline: none;  /* prevents dotted line when link is active */
}

Here is another way to hide the text while avoiding the huge 9999 pixel box that the browser will create:

h1 {
    background-image: url(/the_img.png);  /* shows image */
    height: 100px;                        /* be sure to set height & width */
    width:  600px;

    /* Hide the text. */
    text-indent: 100%;
    white-space: nowrap;
    overflow: hidden;
}

Html – When to use IMG vs. CSS background-image

Proper uses of IMG

Use IMG if you intend to have people print your page and you want the image to be included by default. —JayTee
Use IMG (with alt text) when the image has an important semantic meaning, such as a warning icon. This ensures that the meaning of the image can be communicated in all user-agents, including screen readers.

Pragmatic uses of IMG

Use IMG plus alt attribute if the image is part of the content such as a logo or diagram or person (real person, not stock photo people). —sanchothefat
Use IMG if you rely on browser scaling to render an image in proportion to text size.
Use IMG for multiple overlay images in IE6.
~~Use IMG with a z-index in order to stretch a background image to fill its entire window.~~
Note, this is no longer true with CSS3 background-size; see #6 below.
Using img instead of background-image can dramatically improve performance of animations over a background.

When to use CSS background-image

Use CSS background images if the image is not part of the content. —sanchothefat
Use CSS background images when doing image-replacement of text eg. paragraphs/headers. —sanchothefat
Use background-image if you intend to have people print your page and you do not want the image to be included by default. —JayTee
Use background-image if you need to improve download times, as with CSS sprites.
Use background-image if you need for only a portion of the image to be visible, as with CSS sprites.
Use background-image with background-size:cover in order to stretch a background image to fill its entire window.