2011-09-13[C#生成缩略图]

 /// <summary>
/// 生成缩略图
/// </summary>
/// <param name="originalImagePath">源图路径（物理路径）</param>
/// <param name="thumbnailPath">缩略图路径（物理路径）</param>
/// <param name="width">缩略图宽度</param>
/// <param name="height">缩略图高度</param>

public void CreateMinImage(string originalImagePath,string thumbnailPath,int width, int height)
{
System.Drawing.Image originalImage = System.Drawing.Image.FromFile(HttpContext.Current.Server.MapPath(originalImagePath));

int towidth= width;
int toheight= height;

int ow = originalImage.Width;
int oh = originalImage.Height;

//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));

try
{
//以jpg格式保存缩略图
string FileExt= Path.GetFileNameWithoutExtension(originalImagePath);
//这里报错 bitmap.Save(HttpContext.Current.Server.MapPath(thumbnailPath) + FileExt + ".jpg", System.Drawing.Imaging.ImageFormat.Jpeg);
}
catch (System.Exception e)
{
throw e;
}
finally
{
originalImage.Dispose();
bitmap.Dispose();
g.Dispose();
}

}

//修改后的代码
public void CreateMinImageAndDel(string originalImagePath,string thumbnailPath,int width,int height)
{
Graphics draw =null;
string FileExt="";

System.Drawing.Image originalImage = System.Drawing.Image.FromFile(HttpContext.Current.Server.MapPath(originalImagePath));

int towidth= width;
int toheight= height;

int ow = originalImage.Width;
int oh = originalImage.Height;

//新建一个bmp图片
System.Drawing.Image bitmap =new System.Drawing.Bitmap(towidth, toheight);
System.Drawing.Image bitmap2 =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));

try
{
//以jpg格式保存缩略图
FileExt = Path.GetFileNameWithoutExtension(originalImagePath);
　　　　　　　　　　//用新建立的image对象拷贝bitmap对象 让g对象可以释放资源
draw = Graphics.FromImage(bitmap2);
draw.DrawImage(bitmap, 0,0);

}
catch (System.Exception e)
{
throw e;
}
finally
{
originalImage.Dispose();
bitmap.Dispose();
g.Dispose();
　　　　　　　　　　//保存调整在这里即可
bitmap2.Save(HttpContext.Current.Server.MapPath(thumbnailPath) + FileExt+".jpg", System.Drawing.Imaging.ImageFormat.Jpeg);
}
}