js 完成对图片的等比例缩放的方法

/*
    重新按比例设置 页面上对应图片的长和高，
 */
function resetImgSize(id,imgWidth,imgHeight,posWidth,posHeight) {
    var width = 0;
    var height = 0;
    // 按比例缩小图片的算法
    if(imgWidth > imgHeight) {
        if(imgWidth > posWidth) {
            width = posWidth;
            height = imgHeight/imgWidth * width;
            
        }else {
            width = imgWidth;
            height = imgHeight;
        }
    }else {
        if(imgHeight > posHeight) {
            height = posHeight;
            width = (imgWidth/imgHeight) * height;
        }else {
            width = imgWidth;
            height = imgHeight;
        }
    }
    width = Math.floor(width);
    height = Math.floor(height);
    $('#'+id).attr('width',width);
    $('#'+id).attr('height',height);
    $('#'+id).css('padding-left',(posWidth-width)/2);
    $('#'+id).css('padding-top',(posHeight-height)/2);

}

/*
    获取图片尺寸
    imgURL  图片加载地址
    posId   图片位置id
    posWidth 放在图片位置的width
    posHeight 放在图片位置的height
 */

function getImgSize(imgURL,posId,posWidth,posHeight) {

    var img = new Image();
     

    img.src = imgURL+'?'+Math.random();
    var width = 0;
    var height = 0;
    

    var check = function(){

        if(img.width > 0) {

        clearInterval(set);
        
        resetImgSize(posId,img.width,img.height,posWidth,posHeight);
        }
    };
     
    var set = setInterval(check,40);

    img.onload = function(){
        
        clearInterval(set);
    };

    
}

$(function(){
    $('.resetsize').each(function(){
        getImgSize(this.src,this.id,168,168);
    });
});