js脚本控制图片水平与垂直居中

 1 function ResizeImg(obj) {
 2     var boxHeight = $(".box").height();
 3     var boxWidth = $(".box").width();
 4     var imgHeight = $(obj).height();
 5     var imgWidth = $(obj).width();
 6     if (imgHeight * boxWidth >= imgWidth * boxHeight) {
 7         //调整后,高度超出的情况
 8         var afterImgHeight = boxWidth * imgHeight / imgWidth;
 9         $(obj).css("width", boxWidth + "px").css("height", afterImgHeight + "px");
10         var offsetTop = (afterImgHeight / 2) - (boxHeight / 2);
11         $(obj).css("top", "-" + offsetTop + "px"); //  -20px
12     }
13     else {
14         //调整后,宽度超出的情况
15         var afterImgWidth = boxHeight * imgWidth / imgHeight;
16         $(obj).css("height", boxHeight + "px").css("width", afterImgWidth + "px");
17         var offsetLeft = (afterImgWidth / 2) - (boxWidth / 2);
18         $(obj).css("left", "-" + offsetLeft + "px"); //  -20px
19     }
20     console.log("resize ok.");
21 }