jquery实现图片悬浮效果

主要的想法是当鼠标悬浮后计算所有的描述容器大小和位置。主要依赖于缩略图的最大尺寸及其居于主要wrapper中的位置。例如，当缩略图接近边缘，我们就使得描述区域显示在缩略图左边

然后我们将帮定逼近事件到图片。主要想法是根据鼠标位置来变化图片大小。一旦图片达到最大尺寸，我们设置z-index最高，因此位于最高层次，并且显示分开的描述。风之境地

// list of thumbs

var $list        = $('#pe-thumbs'),

// list's width and offset left.

// this will be used to know the position of the description container

listW        = $list.width(),

listL        = $list.offset().left,

// the images

$elems        = $list.find('img'),

// the description containers

$descrp        = $list.find('div.pe-description'),

// maxScale : maximum scale value the image will have

// minOpacity / maxOpacity : minimum (set in the CSS) and maximum values for the image's opacity

settings    = {

maxScale    : 1.3,

maxOpacity    : 0.9,

minOpacity    : Number( $elems.css('opacity') )

},

init        = function() {

// minScale will be set in the CSS

settings.minScale = _getScaleVal() || 1;

// preload the images (thumbs)

_loadImages( function() {

_calcDescrp();

_initEvents();

});

},

// Get Value of CSS Scale through JavaScript:

// http://css-tricks.com/get-value-of-css-rotation-through-javascript/

_getScaleVal= function() {

var st = window.getComputedStyle($elems.get(0), null),

tr = st.getPropertyValue("-webkit-transform") ||

st.getPropertyValue("-moz-transform") ||

st.getPropertyValue("-ms-transform") ||

st.getPropertyValue("-o-transform") ||

st.getPropertyValue("transform") ||

"fail...";

if( tr !== 'none' ) {

var values = tr.split('(')[1].split(')')[0].split(','),

a = values[0],

b = values[1],

c = values[2],

d = values[3];

return Math.sqrt( a * a + b * b );

}

},

// calculates the style values for the description containers,

// based on the settings variable

_calcDescrp    = function() {

$descrp.each( function(i) {

var $el        = $(this),

$img    = $el.prev(),

img_w    = $img.width(),

img_h    = $img.height(),

img_n_w    = settings.maxScale * img_w,

img_n_h    = settings.maxScale * img_h,

space_t = ( img_n_h - img_h ) / 2,

space_l = ( img_n_w - img_w ) / 2;

$el.data( 'space_l', space_l ).css({

height    : settings.maxScale * $el.height(),

top        : -space_t,

left    : img_n_w - space_l

});

});

},

_initEvents    = function() {

$elems.on('proximity.Photo', { max: 80, throttle: 10, fireOutOfBounds : true }, function(event, proximity, distance) {

var $el            = $(this),

$li            = $el.closest('li'),

$desc        = $el.next(),

scaleVal    = proximity * ( settings.maxScale - settings.minScale ) + settings.minScale,

scaleExp    = 'scale(' + scaleVal + ')';

// change the z-index of the element once

// it reaches the maximum scale value

// also, show the description container

if( scaleVal === settings.maxScale ) {

$li.css( 'z-index', 1000 );

if( $desc.offset().left + $desc.width() > listL + listW ) {

$desc.css( 'left', -$desc.width() - $desc.data( 'space_l' ) );

}

$desc.fadeIn( 800 );

}

else {

$li.css( 'z-index', 1 );

$desc.stop(true,true).hide();

}

$el.css({

'-webkit-transform'    : scaleExp,

'-moz-transform'    : scaleExp,

'-o-transform'        : scaleExp,

'-ms-transform'        : scaleExp,

'transform'            : scaleExp,

'opacity'            : ( proximity * ( settings.maxOpacity - settings.minOpacity ) + settings.minOpacity )

});

});

},

_loadImages    = function( callback ) {

var loaded     = 0,

total    = $elems.length;

$elems.each( function(i) {

var $el = $(this);

            $('').load( function() {

++loaded;

if( loaded === total )

callback.call();

}).attr( 'src', $el.attr('src') );

});

};

return {

init    : init

};