JavaScript

放大镜

<SCRIPT language=JavaScript>
<!-- Beginning of JavaScript -
var isNav, isIE
var offsetX, offsetY
var selectedObj

var enlargefactor=5

var largewidth = 455 //图像的宽度
var largeheight = 523 //图像的高度
var largeleft = 250
var largetop = 30

var thumbwidth = Math.floor(largewidth/enlargefactor)
var thumbheight = Math.floor(largeheight/enlargefactor)
var thumbleft = 50
var thumbtop = 30

var mglasswidth = 32 //放大镜的宽度
var mglassheight = 32 //放大镜的高度
var mglassleft = 120
var mglasstop = 110

var difleft= largeleft-thumbleft
var diftop= largetop-thumbtop

var clippoints

var cliptop = (thumbheight-mglassheight)*enlargefactor
var clipbottom = cliptop+(mglassheight*enlargefactor)
var clipleft =(thumbwidth-mglasswidth)*enlargefactor
var clipright = clipleft+(mglasswidth*enlargefactor)

if (parseInt(navigator.appVersion) >= 4) {
if (navigator.appName == "Netscape") {
isNav = true
} else {
isIE = true
}
}

function setZIndex(obj, zOrder) {
obj.zIndex = zOrder
}

function shiftTo(obj, x, y) {
if (isNav) {
obj.moveTo(x,y)
} else {
obj.pixelLeft = x
obj.pixelTop = y
}
cliptop = (y-thumbtop)*enlargefactor
clipbottom = cliptop+(mglassheight*enlargefactor)
clipleft = (x-thumbleft)*enlargefactor
clipright = clipleft+(mglasswidth*enlargefactor)

if (document.all) {
clippoints ="rect("+cliptop+" "+clipright+" "+clipbottom+" "+clipleft+")"
document.all.large.style.posTop=largetop-cliptop
document.all.large.style.posLeft=largeleft-clipleft
document.all.large.style.clip=clippoints
}
if (document.layers) {
document.large.top=largetop-cliptop
document.large.left=largeleft-clipleft
document.large.clip.left = clipleft
document.large.clip.right = clipright
document.large.clip.top = cliptop
document.large.clip.bottom = clipbottom
}
}

function setSelectedElem(evt) {
if (isNav) {
var testObj
var clickX = evt.pageX
var clickY = evt.pageY
for (var i = document.layers.length - 1; i >= 0; i--) {
testObj = document.layers[i]
if ((clickX > testObj.left) &&
(clickX < testObj.left + testObj.clip.width) &&
(clickY > testObj.top) &&
(clickY < testObj.top + testObj.clip.height)) {
selectedObj = testObj
setZIndex(selectedObj, 100)
return
}
}
} else {
var imgObj = window.event.srcElement
if (imgObj.parentElement.id.indexOf("mglass") != -1) {
selectedObj = imgObj.parentElement.style
setZIndex(selectedObj,100)
return
}
}
selectedObj = null
return
}

function dragIt(evt) {
if (selectedObj) {
if (isNav) {
shiftTo(selectedObj, (evt.pageX - offsetX), (evt.pageY - offsetY))
} else {
shiftTo(selectedObj, (window.event.clientX - offsetX), (window.event.clientY - offsetY))
return false
}
}
}

function engage(evt) {
setSelectedElem(evt)
if (selectedObj) {
if (isNav) {
offsetX = evt.pageX - selectedObj.left
offsetY = evt.pageY - selectedObj.top
} else {
offsetX = window.event.offsetX
offsetY = window.event.offsetY
}
}
return false
}

function release(evt) {
if (selectedObj) {
setZIndex(selectedObj, 0)
selectedObj = null
}
}

function setNavEventCapture() {
if (isNav) {
document.captureEvents(Event.MOUSEDOWN | Event.MOUSEMOVE | Event.MOUSEUP)
}
}

function init() {

if (document.layers) {
document.large.left=largeleft
document.large.top=largetop

document.framegif.left=largeleft-3
document.framegif.top=largetop-3

document.thumb.left=thumbleft
document.thumb.top=thumbtop

document.mglass.left=mglassleft
document.mglass.top=mglasstop

document.large.clip.left = 0
document.large.clip.right = 0
document.large.clip.top = 0
document.large.clip.bottom = 0

setNavEventCapture()
}

if (document.all) {
document.all.large.style.posLeft=largeleft
document.all.large.style.posTop=largetop

document.all.framegif.style.posLeft=largeleft-3
document.all.framegif.style.posTop=largetop-3

document.all.thumb.style.posLeft=thumbleft
document.all.thumb.style.posTop=thumbtop

document.all.mglass.style.posLeft=mglassleft
document.all.mglass.style.posTop=mglasstop
document.all.large.style.clip="rect(0 0 0 0)"
}

document.onmousedown = engage
document.onmousemove = dragIt
document.onmouseup = release
}
// - End of JavaScript - -->
</SCRIPT>
</HEAD>
<BODY onload=init()>
<DIV id=thumb><IMG name=thumbpic src="../image/7_JS_8_p1.jpg" width=91></DIV>
<DIV id=framegif><IMG name=framepic src="../image/7_JS_8_p2.gif"></DIV>
<DIV id=large><IMG name=largepic src="../image/7_JS_8_p1.jpg" width=455></DIV>
<DIV id=mglass><IMG name=mglasspic
src="../image/7_JS_8_p3.gif"></DIV></BODY>