C#生成缩略图

C#生成缩略图：

用数据库保存图片的路径和文件名称，把文件保存在文件夹中.

//保存在数据库中的文件路径

ArrayList arrFilePath=new ArrayList();

arrFilePath=myCommonMethod.UploadPic(Files,"/UpLoads/UpPicture/");

//获取文件名称

string fileName=arrFilePath[0].SubString(arrFilePath[0].LastIndexOf("/")+1);

//源图路径（物理路径）

originalImagePath=Request.PhysicalApplicationPath+"/UpLoads/UpPicture/"+fileName;

//缩略图路径（物理路径）

thumbnailPath =Request.PhysicalApplicationPath+"/UpLoads/UpPicture/"+"thumb_"+fileName;

//调用生成缩略图方法

this.MakeThumbnail(originalImagePath,thumbnailPath,120,150, strMode out outthumbnailPath);

#region 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>

/// <param name="mode">生成缩略图的方式</param>

public void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode out string outthumbnailPath)

{

System.Drawing.Image originalImage =System.Drawing.Image.FromFile(originalImagePath);

int towidth = width;

int toheight = height;

int x = 0;

int y = 0;

int ow = originalImage.Width;

int oh = originalImage.Height;

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

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(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 Rectangle(0, 0, towidth, toheight),

new Rectangle(x, y, ow,oh),

GraphicsUnit.Pixel);

try

{

//以jpg格式保存缩略图

bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);

outthumbnailPath=thumbnailPath;

}

catch(System.Exception e)

{

throw e;

}

finally

{

originalImage.Dispose();

bitmap.Dispose();

g.Dispose();

}

}