Asp.net 实现图片缩放 无水印（方法二）

public static System.Drawing.Image GetImage(string path)
{
try
{
if (path.StartsWith("http"))//获取远程图片
{
System.Net.WebRequest request = System.Net.WebRequest.Create(path);
request.Timeout = 10000;
System.Net.HttpWebResponse httpresponse = (System.Net.HttpWebResponse)request.GetResponse();
Stream s = httpresponse.GetResponseStream();
return System.Drawing.Image.FromStream(s);
}
else//获取本地图片
{
return System.Drawing.Image.FromFile(path);
}
}
catch (Exception ex) { return null; }
}

public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
{
System.Drawing.Image originalImage = GetImage(originalImagePath);// System.Drawing.Image.FromFile(HttpContext.Current.Server.MapPath(originalImagePath));
if (originalImage == null)
return;
int towidth = width;
int toheight = height;

int x = 0;
int y = 0;
int ow = originalImage.Width;
int oh = originalImage.Height;

if (mode == "EQU")//指定最大高宽，等比例缩放
{
//if(height/oh>width/ow),如果高比例多，按照宽来缩放；如果宽的比例多，按照高来缩放
if (height * ow > width * oh)
{
mode = "W";
}
else
{
mode = "H";
}
}
switch (mode)
{
case "HW"://指定高宽缩放（可能变形）
break;
case "W"://指定宽，高按比例
toheight = originalImage.Height * width / originalImage.Width;
break;
case "H"://指定高，宽按比例
towidth = originalImage.Width * height / originalImage.Height;
break;
case "Cut"://指定高宽裁减（不变形）
if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)
{
oh = originalImage.Height;
ow = originalImage.Height * towidth / toheight;
y = 0;
x = (originalImage.Width - ow) / 2;
}
else
{
ow = originalImage.Width;
oh = originalImage.Width * height / towidth;
x = 0;
y = (originalImage.Height - oh) / 2;
}
break;
default:
break;
}

//新建一个bmp图片
System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);

//新建一个画板
System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);

//设置高质量插值法
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

//设置高质量,低速度呈现平滑程度
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

//清空画布并以透明背景色填充
g.Clear(System.Drawing.Color.Transparent);

//在指定位置并且按指定大小绘制原图片的指定部分
g.DrawImage(originalImage, new System.Drawing.Rectangle(0, 0, towidth, toheight),
new System.Drawing.Rectangle(x, y, ow, oh),
System.Drawing.GraphicsUnit.Pixel);
try
{
//以jpg格式保存缩略图
bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
}
catch (System.Exception e)
{
throw e;
}
finally
{
originalImage.Dispose();
bitmap.Dispose();
g.Dispose();
}
}