图片区域放大

效果:

用鼠标移动下面的方框，效果不错吧

代码：

<SCRIPT>

var shrinkfactor=5

// left and top position of the thumbnailimage 
// (distance to the left and top browser-margin, pixels)
var thumbleft = 30
var thumbtop = 30

// left and top position of the zoomed image 
// (distance to the left and top browser-margin, pixels)
var largeleft = 300
var largetop = 30

// width and height of the enlarged image's sector (visible part, pixels)
var clipwidth = 240
var clipheight = 160
</SCRIPT>

<SCRIPT>

var isNav, isIE
var offsetX, offsetY
var selectedObj 

var largewidth = 0
var largeheight = 0

var thumbwidth = Math.floor(largewidth/shrinkfactor)
var thumbheight = Math.floor(largeheight/shrinkfactor)

var dragimgwidth = Math.floor(clipwidth/shrinkfactor)
var dragimgheight = Math.floor(clipheight/shrinkfactor)
var dragimgleft = thumbleft+3
var dragimgtop = thumbtop+3

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

var clippoints

var cliptop=0
var clipbottom=cliptop+clipheight
var clipleft=0
var clipright=clipleft+clipwidth


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) {
        if(x<=document.thumb.left) {x=document.thumb.left}
        if(x>=(document.thumb.left+thumbwidth-dragimgwidth-2)) {x=document.thumb.left+thumbwidth-dragimgwidth-2}
        if(y<=document.thumb.top) {y=document.thumb.top}
        if(y>=(document.thumb.top+thumbheight-dragimgheight-2)) {y=document.thumb.top+thumbheight-dragimgheight-2}
        obj.moveTo(x,y)
    } else {
        if(x<=document.all.thumb.style.posLeft) {x=document.all.thumb.style.posLeft}
        if(x>=(document.all.thumb.style.posLeft+thumbwidth-dragimgwidth-2)) {x=document.all.thumb.style.posLeft+thumbwidth-

dragimgwidth-2}
        if(y<=document.all.thumb.style.posTop) {y=document.all.thumb.style.posTop}
        if(y>=(document.all.thumb.style.posTop+thumbheight-dragimgheight-2)) {y=document.all.thumb.style.posTop+thumbheight-

dragimgheight-2}
        obj.pixelLeft = x
        obj.pixelTop = y
    }    
    cliptop = (y-thumbtop)*shrinkfactor
    clipbottom = cliptop+clipheight
    clipleft = (x-thumbleft)*shrinkfactor
    clipright = clipleft+clipwidth

    
    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 && document.layers[i].id=="dragimg")) {
                    selectedObj = testObj
                    setZIndex(selectedObj, 100)
                    return
            }
        }
    } else {
        var imgObj = window.event.srcElement
        if (imgObj.parentElement.id.indexOf("dragimg") != -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) {
        var imageurl=document.large.document.largepic.src
        largewidth=document.large.document.width
        largeheight=document.large.document.height
        thumbwidth = Math.floor(largewidth/shrinkfactor)
        thumbheight = Math.floor(largeheight/shrinkfactor)
        document.thumb.document.write("<IMG NAME='thumbpic' SRC='"+imageurl+"' width="+thumbwidth+"  

height="+thumbheight+">")
        document.thumb.document.close()
        document.dragimg.document.write("<IMG NAME='dragimgpic' border=2 SRC='dragimg.gif' width="+dragimgwidth+" 

height="+dragimgheight+">")
        document.dragimg.document.close()
        document.large.left=largeleft
        document.large.top=largetop
    
        document.thumb.left=thumbleft
        document.thumb.top=thumbtop
    
        document.dragimg.left=dragimgleft
        document.dragimg.top=dragimgtop
        
        document.large.clip.left=clipleft
        document.large.clip.right=clipright
        document.large.clip.top=cliptop
        document.large.clip.bottom=clipbottom
        document.large.visibility="visible"
        
        setNavEventCapture()
    }
    if (document.all) {
        var imageurl=document.largepic.src
        largewidth=document.all.large.offsetWidth
        largeheight=document.all.large.offsetHeight
        thumbwidth = Math.floor(largewidth/shrinkfactor)
        thumbheight = Math.floor(largeheight/shrinkfactor)
        thumb.innerHTML="<IMG NAME='thumbpic' SRC='"+imageurl+"' width="+thumbwidth+"  height="+thumbheight+">"
        dragimg.innerHTML="<IMG NAME='dragimgpic' border=2 SRC='http://www.jscode.cn/Uploadfile/200651515151450.GIF' 

width="+dragimgwidth+"  height="+dragimgheight+">"
    
        document.all.large.style.posLeft=largeleft
        document.all.large.style.posTop=largetop
    
        document.all.thumb.style.posLeft=thumbleft
        document.all.thumb.style.posTop=thumbtop
    
        document.all.dragimg.style.posLeft=dragimgleft
        document.all.dragimg.style.posTop=dragimgtop
        clippoints ="rect("+cliptop+" "+clipright+" "+clipbottom+" "+clipleft+")"
        document.all.large.style.clip=clippoints
        document.all.large.style.visibility="visible"
    }
    
    document.onmousedown = engage
    document.onmousemove = dragIt
    document.onmouseup = release
}

window.onload=init
</SCRIPT>


<P>用鼠标移动下面的方框，效果不错吧</P>
<CENTER>
<DIV id=large style="VISIBILITY: hidden; POSITION: absolute">
<IMG src="http://images.cnblogs.com/cnblogs_com/badegg/163780/r_me.jpg" name=largepic>
</DIV>
<DIV id=thumb style="POSITION: absolute"></DIV>
<DIV id=dragimg style="POSITION: absolute"></DIV></CENTER>