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Created May 14, 2019

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Creating An Image Zoom And Clip Effect With jQuery
<!DOCTYPE HTML>
<html>
<head>
<title>Image Zoom With jQuery</title>
<style type="text/css">
#view {
border: 1px solid #333333 ;
overflow: hidden ;
position: relative ;
width: 400px ;
}
#image {
display: block ;
left: 0px ;
top: 0px ;
}
#zoom {
background-image: url( "./white_fade.png" ) ;
border: 1px solid #000000 ;
cursor: pointer ;
display: none ;
height: 200px ;
position: absolute ;
width: 200px ;
z-index: 100 ;
}
</style>
<script type="text/javascript" src="../jquery-1.4.js"></script>
<script type="text/javascript">
// When the WINDOW is ready, initialize. We are going with
// the window load rather than the document so that we
// know our image will be ready as well (complete with
// gettable dimentions).
$( window ).load(function(){
// First, let's get refernces to the elements we will
// be using.
var view = $( "#view" );
var image = $( "#image" );
// Create the ZOOM element - this will be added with
// Javascript since it's more of an "effect".
var zoom = $( "<a id='zoom'><span><br /></span></a>" );
// Before we start messing with the scripts, let's
// update the display to allow for the absolute
// positioning of the image and zoomer.
// Set an explicit height / width on the view based
// on the initial size of the image.
view.width( image.width() );
view.height( image.height() );
// Now that the view has an explicit width and height,
// we can change the displays for positioning.
image.css( "position", "absolute" );
// Set an exlicit height on the image (to make sure
// that some of the later calcualtions don't get
// messed up - I saw some irradic caculated-height
// behavior).
image.height( image.height() );
// Before we add the zoom square, we need it to match
// the aspect ratio of the image.
zoom.width( Math.floor( image.width() / 2 ) );
zoom.height( Math.floor( image.height() / 2 ) );
// Now, add the zoom square to the view.
view.append( zoom );
// ---------------------------------------------- //
// ---------------------------------------------- //
// Now that we have our UI set up physically, we need
// to bind the event handlers.
// We want to show and hide the zoom only when the
// user hovers over the view.
view.hover(
function( event ){
// Show the soom.
zoom.show();
},
function( event ){
// Hide the zoom.
zoom.hide();
}
);
// As the user mouses over the view, we can get the
// mouse coordinates in terms of the page; we need
// to be able to translate those into VIEW-based
// X and Y cooridates. As such, let's get the offset
// of the view as our base 0x0 coordinate.
//
// NOTE: We are doing this here so that we do it once,
// rather than every time the mouse moves.
viewOffset = view.offset();
// Get the jQuery-ed version of the window as we will
// need to access it's scroll offsets every time the
// mouse moves over the div.
//
// NOTE: This will change the change the refernce to
// "window" for all of the code in this closure.
var window = $( window );
// As the user moves across the view, we want to move
// the zoom square with them.
view.mousemove(
function( event ){
// Get the window scroll top; the mouse
// position is relative to the window, NOT
// the document.
var windowScrollTop = window.scrollTop();
var windowScrollLeft = window.scrollLeft();
// Translate the mouse X / Y into view-local
// coordinates that can be used to position
// the zoom box.
setZoomPosition(
Math.floor(
event.clientX - viewOffset.left + windowScrollLeft
),
Math.floor(
event.clientY - viewOffset.top + windowScrollTop
)
);
}
);
// I position the zoom box within the view based on
// the given view-local mouse coordinates.
var setZoomPosition = function( mouseLeft, mouseTop ){
// Ideally, we want to keep the zoom box centered
// on the mouse. As such, we want the given mouse
// left and mouse top coordiantes to be in the
// middle of the zoom box.
var zoomLeft = (mouseLeft - (zoom.width() / 2));
var zoomTop = (mouseTop - (zoom.height() / 2))
// As we move the zoom box around, however, we
// never want it to go out of bounds of the view.
// Protect the top-left bounds.
zoomLeft = Math.max( zoomLeft, 0 );
zoomTop = Math.max( zoomTop, 0 );
// Protect the bottom-right bounds. Because the
// bottom and right need to take the dimensions
// of the zoom box into account, be sure to use
// the outer width to include the border.
zoomLeft = Math.min(
zoomLeft,
(view.width() - zoom.outerWidth())
);
zoomTop = Math.min(
zoomTop,
(view.height() - zoom.outerHeight())
);
// Position the zoom box in the bounds of the
// image view box.
zoom.css({
left: (zoomLeft + "px"),
top: (zoomTop + "px")
});
};
// Now that we have the mouse movements being tracked
// properly, we need to track the click on the zoom to
// zoom in the image on demand. To do that, however,
// we need to start storing some information with the
// image so we can manipulate it as needed.
image.data({
zoomFactor: (view.width() / zoom.width()),
zoom: 1,
top: 0,
left: 0,
width: image.width(),
height: image.height(),
originalWidth: image.width(),
originalHeight: image.height()
});
// Now, let's attach the click event handler to the
// zoom box.
zoom.click(
function( event ){
// First, prevent the default since this is
// not a navigational link.
event.preventDefault();
// Let's pass the position of the zoom box
// off to the function that is responsible
// for zooming the image.
zoomImage(
zoom.position().left,
zoom.position().top
);
}
);
// I take the zoom box coordinates and translate them
// into an actual image zoom based on the existing
// zoom and offset of the image.
//
// NOTE: We don't care about the dimensions of the
// zoom box itself as those should have already been
// properly translated into the zoom *factor*.
var zoomImage = function( zoomLeft, zoomTop ){
// Get a reference to the image data object so we
// don't need to keep retreiving it.
var imageData = image.data();
// Check to see if we have reached the max zoom
// or if the image is currently animating.
// If so, just return out.
if (
(imageData.zoom == 5) ||
(image.is( ":animated" ))
){
// Zooming in beyond this is pointless (and
// can cause the browser to mis-render the
// image).
return;
}
// Scale the image up based on the zoom factor.
imageData.width =
(image.width() * imageData.zoomFactor);
imageData.height =
(image.height() * imageData.zoomFactor);
// Change the offset set data to re-position the
// 0,0 coordinate back up in the top left.
imageData.left =
((imageData.left - zoomLeft) * imageData.zoomFactor);
imageData.top =
((imageData.top - zoomTop) * imageData.zoomFactor);
// Increase the zoom.
imageData.zoom++;
// Animate the zoom.
image.animate(
{
width: imageData.width,
height: imageData.height,
left: imageData.left,
top: imageData.top
},
500
);
};
// I reset the image zoom.
var resetZoom = function(){
// Get a reference to the image data object so we
// don't need to keep retreiving it.
var imageData = image.data();
// Reset the image data.
imageData.zoom = 1;
imageData.top = 0;
imageData.left = 0;
imageData.width = imageData.originalWidth;
imageData.height = imageData.originalHeight;
// Animate the zoom.
image.animate(
{
width: imageData.width,
height: imageData.height,
left: imageData.left,
top: imageData.top
},
300
);
};
// As a final step, to make sure that the image can
// be zoomed out, bind the mousedown to the document.
$( document ).mousedown(
function( event ){
// Check to see if the view is in the event
// bubble chain for the mouse down. If it is,
// then this click was in the view or its
// child elements.
var closestView = $( event.target ).closest( "#view" );
// Check to see if this mouse down was in the
// image view.
if (!closestView.size()){
// The view was not found in the chain.
// This was clicked outside of the view.
// Reset the image zoom.
resetZoom();
}
}
);
});
</script>
</head>
<body>
<h1>
Image Zoom And Clip With jQuery
</h1>
<div id="view">
<img id="image" src="./girl.jpg" width="400" />
</div>
</body>
</html>
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