c#中怎么實現一個生成圖片縮略圖的類

c#中怎么實現一個生成圖片縮略圖的類，相信很多沒有經驗的人對此束手無策，為此本文總結了問題出現的原因和解決方法，通過這篇文章希望你能解決這個問題。

第一種

復制代碼 代碼如下:

/**//// <summary>
/// 生成縮略圖
/// </summary>
/// <param name="originalImagePath">源圖路徑（物理路徑）</param>
/// <param name="thumbnailPath">縮略圖路徑（物理路徑）</param>
/// <param name="width">縮略圖寬度</param>
/// <param name="height">縮略圖高度</param>
/// <param name="mode">生成縮略圖的方式</param>
public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
{
Image originalImage = 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"://指定高寬縮放（可能變形）
break;
case "W"://指定寬，高按比例
toheight = originalImage.Height * width/originalImage.Width;
break;
case "H"://指定高，寬按比例
towidth = originalImage.Width * height/originalImage.Height;
break;
case "Cut"://指定高寬裁減（不變形）
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;
}
//新建一個bmp圖片
Image bitmap = new System.Drawing.Bitmap(towidth,toheight);
//新建一個畫板
Graphics g = System.Drawing.Graphics.FromImage(bitmap);
//設置高質量插值法
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
//設置高質量,低速度呈現平滑程度
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
//清空畫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繪制原圖片的指定部分
g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight),
new Rectangle(x, y, ow,oh),
GraphicsUnit.Pixel);
try
{
//以jpg格式保存縮略圖
bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
}
catch(System.Exception e)
{
throw e;
}
finally
{
originalImage.Dispose();
bitmap.Dispose();
g.Dispose();
}
}

關鍵方法Graphics.DrawImage見ms-help://MS.NETFrameworkSDKv1.1.CHS/cpref/html/frlrfsystemdrawinggraphicsclassdrawimagetopic11.htm
第二種
4個重載方法,有直接返回Image對象的,有生成縮略圖,并且保存到指定目錄的!

復制代碼 代碼如下:

using System.IO;
using System.Drawing;
using System.Drawing.Imaging;
/// <summary>
/// 圖片處理類
/// 1、生成縮略圖片或按照比例改變圖片的大小和畫質
/// 2、將生成的縮略圖放到指定的目錄下
/// </summary>
public class ImageClass
{
public Image ResourceImage;
private int ImageWidth;
private int ImageHeight;
public string ErrMessage;
/// <summary>
/// 類的構造函數
/// </summary>
/// <param name="ImageFileName">圖片文件的全路徑名稱</param>
public ImageClass(string ImageFileName)
{
ResourceImage=Image.FromFile(ImageFileName);
ErrMessage="";
}
public bool ThumbnailCallback()
{
return false;
}
/// <summary>
/// 生成縮略圖重載方法1，返回縮略圖的Image對象
/// </summary>
/// <param name="Width">縮略圖的寬度</param>
/// <param name="Height">縮略圖的高度</param>
/// <returns>縮略圖的Image對象</returns>
public Image GetReducedImage(int Width,int Height)
{
try
{
Image ReducedImage;
Image.GetThumbnailImageAbort callb=new Image.GetThumbnailImageAbort(ThumbnailCallback);
ReducedImage=ResourceImage.GetThumbnailImage(Width,Height,callb,IntPtr.Zero);
return ReducedImage;
}
catch(Exception e)
{
ErrMessage=e.Message;
return null;
}
}
/// <summary>
/// 生成縮略圖重載方法2，將縮略圖文件保存到指定的路徑
/// </summary>
/// <param name="Width">縮略圖的寬度</param>
/// <param name="Height">縮略圖的高度</param>
/// <param name="targetFilePath">縮略圖保存的全文件名，(帶路徑)，參數格式：D:Images ilename.jpg</param>
/// <returns>成功返回true，否則返回false</returns>
public bool GetReducedImage(int Width,int Height,string targetFilePath)
{
try
{
Image ReducedImage;
Image.GetThumbnailImageAbort callb=new Image.GetThumbnailImageAbort(ThumbnailCallback);
ReducedImage=ResourceImage.GetThumbnailImage(Width,Height,callb,IntPtr.Zero);
ReducedImage.Save(@targetFilePath,ImageFormat.Jpeg);
ReducedImage.Dispose();
return true;
}
catch(Exception e)
{
ErrMessage=e.Message;
return false;
}
}
/// <summary>
/// 生成縮略圖重載方法3，返回縮略圖的Image對象
/// </summary>
/// <param name="Percent">縮略圖的寬度百分比 如：需要百分之80，就填0.8</param>
/// <returns>縮略圖的Image對象</returns>
public Image GetReducedImage(double Percent)
{
try
{
Image ReducedImage;
Image.GetThumbnailImageAbort callb=new Image.GetThumbnailImageAbort(ThumbnailCallback);
ImageWidth=Convert.ToInt32(ResourceImage.Width*Percent);
ImageHeight=Convert.ToInt32(ResourceImage.Width*Percent);
ReducedImage=ResourceImage.GetThumbnailImage(ImageWidth,ImageHeight,callb,IntPtr.Zero);
return ReducedImage;
}
catch(Exception e)
{
ErrMessage=e.Message;
return null;
}
}
/// <summary>
/// 生成縮略圖重載方法4，返回縮略圖的Image對象
/// </summary>
/// <param name="Percent">縮略圖的寬度百分比 如：需要百分之80，就填0.8</param>
/// <param name="targetFilePath">縮略圖保存的全文件名，(帶路徑)，參數格式：D:Images ilename.jpg</param>
/// <returns>成功返回true,否則返回false</returns>
public bool GetReducedImage(double Percent,string targetFilePath)
{
try
{
Image ReducedImage;
Image.GetThumbnailImageAbort callb=new Image.GetThumbnailImageAbort(ThumbnailCallback);
ImageWidth=Convert.ToInt32(ResourceImage.Width*Percent);
ImageHeight=Convert.ToInt32(ResourceImage.Width*Percent);
ReducedImage=ResourceImage.GetThumbnailImage(ImageWidth,ImageHeight,callb,IntPtr.Zero);
ReducedImage.Save(@targetFilePath,ImageFormat.Jpeg);
ReducedImage.Dispose();
return true;
}
catch(Exception e)
{
ErrMessage=e.Message;
return false;
}
}
}

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