js 按图片比例自动缩放

js 图片自动缩放

function AutoResizeImage(maxWidth,maxHeight,objImg){
			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;
			}
			
//<img src="[%$url%]<?php echo $bannerurl; ?>"  onload="AutoResizeImage(1024,0,this)"/>