控制图片大小的方法有很多，在本文将为大家详细介绍下使用js实现缩放图片，核心代码如下，感兴趣的朋友可以参考下
缩放图片脚本分享
js 控制图片大小-www.jbxue.com 
重点js:
function AutoResizeImage(maxWidth,maxHeight){ var objImg = document.getElementById("operImg"); var img = new Image(); img.src = objImg.src; var hRatio; var wRatio; var Ratio = 1; var w = img.width; var h = img.height; wRatio = maxWidth / w; hRatio = maxHeight / h; if (maxWidth ==0 && maxHeight==0){ Ratio = 1; }else if (maxWidth==0){ // if (hRatio<1) Ratio = hRatio; }else if (maxHeight==0){ if (wRatio<1) Ratio = wRatio; }else if (wRatio<1 || hRatio<1){ Ratio = (wRatio<=hRatio?wRatio:hRatio); } if (Ratio<1){ w = w * Ratio; h = h * Ratio; } objImg.height = h; objImg.width = w; }