js图片宽高自适应及半透明

//改变透明度参数：图片对象，透明度：1-100的值
function setAlpha(imgObj,opacityValue){
imgObj.filters.alpha.opacity=parseInt(opacityValue);
}
//图片的显示大小[以宽度来限制]
function DrawImageW(imgObj,widthValue){
var image=new Image();
image.src=imgObj.src;
if(image.width>0 && image.height>0){
if(image.width>=widthValue){
imgObj.width=widthValue;
imgObj.height=(image.height*widthValue)/image.width;
}else{
imgObj.width=image.width;
imgObj.height=image.height;
}
}
}
//图片的显示大小[以高度来限制]
function DrawImageH(imgObj,heightValue){
var image=new Image();
image.src=imgObj.src;
if(image.width>0 && image.height>0){
if(image.height>=heightValue){
imgObj.height=heightValue;
imgObj.width=(image.width*heightValue)/image.height;
}else{
imgObj.width=image.width;
imgObj.height=image.height;
}
}
}
//图片的显示大小[宽高同时限制]
function DrawImage(imgObj,widthValue,heightValue){
var image=new Image();
image.src=imgObj.src;
if(image.width>0 && image.height>0){
if(image.height>heightValue||image.width>widthValue){
var h=0,w,wflg=false;
if(image.height>heightValue)
wflg=true;
if(wflg){
w=widthValue;
h=(image.height*widthValue)/image.width;
}
if(h==0||h>heightValue){
h=heightValue;
w=(image.width*heightValue)/image.height;
}
//alert(w)
//alert(h)
imgObj.width=w;
imgObj.height=h;
}else{
imgObj.width=image.width;
imgObj.height=image.height;
}
}
}
function zoomImg(imgObj){
var zoom=parseInt(imgObj.style.zoom, 10)||100;zoom+=event.wheelDelta/12;if (zoom>0) imgObj.style.zoom=zoom+'%';
return false;
}