function resizeImage(obj, MaxW, MaxH) { var imageObject = obj; var state = imageObject.readyState; if(state!='complete') { setTimeout("resizeImage("+imageObject+","+MaxW+","+MaxH+")",50); return; } var oldImage = new Image(); oldImage.src = imageObject.src; var dW = oldImage.width; var dH = oldImage.height; if(dW>MaxW || dH>MaxH) { a = dW/MaxW; b = dH/MaxH; if( b>a ) a = b; dW = dW/a; dH = dH/a; } if(dW > 0 && dH > 0) { imageObject.width = dW; imageObject.height = dH; } }
使用很简单：<img src="https://www.jb51.net/pic.jpg" onload='resizeImage(this,60,90)> 就OK了；
注：等比例放缩的时候会出现抖动的情况，处理方法很简单，你在img的属性先设置它的widht和height，这样的话加载的时候绝对不会超过这个尺寸，等你js运行好之后就会调到你所规定的比例，绝对不会以下撑到很大。
同时也附上C#版本的
/// <summary> /// 按比例缩放图片 /// </summary> /// <param>图片的路径</param> /// <param>图片的高度</param> /// <param>图片的宽度</param> /// <returns></returns> public static string GetImageSize(string imgUrl,int imgHeight,int imgWidth) { string fileName = System.Web.HttpContext.Current.Server.MapPath(imgUrl); string strResult = string.Empty; if(System.IO.File.Exists(fileName) && imgHeight != 0 && imgWidth != 0) { decimal desWidth;decimal desHeight;//目标宽高 System.Drawing.Image objImage = System.Drawing.Image.FromFile(fileName); decimal radioAct = (decimal)objImage.Width/(decimal)objImage.Height;//原始图片的宽高比 decimal radioLoc = (decimal)imgWidth/(decimal)imgHeight;//图片位的宽高比 if(radioAct > radioLoc)//原始图片比图片位宽 { decimal dcmZoom = (decimal)imgWidth/(decimal)objImage.Width; desHeight = objImage.Height*dcmZoom; desWidth = imgWidth; } else { decimal dcmZoom = (decimal)imgHeight/(decimal)objImage.Height; desWidth = objImage.Width*dcmZoom; desHeight = imgHeight; } objImage.Dispose(); //释放资源 strResult = "width=\"" + Convert.ToString((int)desWidth) + "\" height=\"" + Convert.ToString((int)desHeight) + "\" "; } return strResult; }
希望本文所述对大家JavaScript程序设计有所帮助。
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