function resizeImg(img,oAW,oAH){
var oimgW = img.width,
oimgH = img.height,
oimg = img,
oY = (oimgH/oimgW).toFixed(2),
oX = (oimgW/oimgH).toFixed(2);
if(oimgW <= oAW&&oimgH <= oAH){//图片高和宽比指定的宽高都小
oimg.style.height = oimgH+'px';
oimg.style.width = oimgW+'px';
} else if(oimgW >= oAW&&oimgH >= oAH){//图片高和宽比指定的宽高都大
if(oY*oAW>=oAH){ //图片高比宽大
oimg.style.height = oAH+'px';
oimg.style.width = oX*oAH+'px';
}else{ //图片高比宽小
oimg.style.height = oY*oAW+'px';
oimg.style.width = oAW+'px';
}
}else if(oimgW>oAW &&oimgH < oAH){//图片宽比指定宽大，高比指定的小
oimg.style.height = oY*oAW+'px';
oimg.style.width = oAW+'px';
}else if(oimgW<oAW &&oimgH > oAH){//图片宽比指定宽小，高比指定的大
oimg.style.height = oAH+'px';
oimg.style.width = oX*oAH+'px';
}
}
function resizeImgMid(img,oAW,oAH){
var oimgW = img.width,
oimgH = img.height,
oimg = img,
oY = (oimgH/oimgW).toFixed(2),
oX = (oimgW/oimgH).toFixed(2);
if(oimgW <= oAW&&oimgH <= oAH){//图片高和宽比指定的宽高都小
oimg.style.height = oimgH+'px';
oimg.style.width = oimgW+'px';
oimg.style.marginLeft = 1/2*(oAW-oimgW)+'px';
oimg.style.marginTop = 1/2*(oAH-oimgH)+'px';
} else if(oimgW >= oAW&&oimgH >= oAH){//图片高和宽比指定的宽高都大
if(oY*oAW>=oAH){ //图片高比宽大
oimg.style.height = oAH+'px';
oimg.style.width = oX*oAH+'px';
oimg.style.marginLeft = 1/2*(oAW-oX*oAH)+'px';
oimg.style.marginTop = 0;
}else{ //图片高比宽小
oimg.style.width = oAW+'px';
oimg.style.height = oY*oAW+'px';
oimg.style.marginLeft = 0;
oimg.style.marginTop = 1/2*(oAH-oY*oAW)+'px';
}
}else if(oimgW>oAW &&oimgH < oAH){//图片宽比指定宽大，高比指定的小
oimg.style.height = oY*oAW+'px';
oimg.style.width = oAW+'px';
oimg.style.marginLeft = 0;
oimg.style.marginTop = 1/2*(oAH-oY*oAW)+'px';
}else if(oimgW<oAW &&oimgH > oAH){//图片宽比指定宽小，高比指定的大
oimg.style.height = oAH+'px';
oimg.style.width = oX*oAH+'px';
oimg.style.marginLeft = 1/2*(oAW-oX*oAH)+'px';
oimg.style.marginTop = 0;
}
}