C#生成缩略图

using System;

using System.Collections.Generic;

using System.Drawing;

using System.Drawing.Drawing2D;

using System.Drawing.Imaging;

using System.Text;

namespace learun.util

{

public enum ThumbnailMode

{

/// <summary>

/// 指定宽度，高度按照比例缩放

/// </summary>

Width = 0,

/// <summary>

/// 指定高度，宽度按照比例缩放

/// </summary>

Height = 1,

/// <summary>

/// 按照指定的高度和宽度剪裁

/// </summary>

Cut = 2,

/// <summary>

/// 指定宽度，高度按照比例缩放

/// </summary>

None = 3

}

public class PicUtil

{

public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, ThumbnailMode mode)

{

System.Drawing.Image img_OriginalImage = null;

ImageFormat tFormat = null;

try

{

img_OriginalImage = (Bitmap)System.Drawing.Image.FromFile(originalImagePath);

tFormat = img_OriginalImage.RawFormat;

}

catch (Exception ex)

{

if (img_OriginalImage != null)

{

img_OriginalImage.Dispose();

}

throw new Exception("压缩图片:" + originalImagePath + "失败！\r\n" + ex.Message);

}

int i_ToWidth = width;

int i_ToHeight = height;

int x = 0;

int y = 0;

int i_OriginalWidth = img_OriginalImage.Width;

int i_OriginalHeight = img_OriginalImage.Height;

switch (mode)

{

case ThumbnailMode.Width:

i_ToHeight = img_OriginalImage.Height * width / img_OriginalImage.Width;

break;

case ThumbnailMode.Height:

i_ToWidth = img_OriginalImage.Width * height / img_OriginalImage.Height;

break;

case ThumbnailMode.Cut:

if ((double)img_OriginalImage.Width / (double)img_OriginalImage.Height > (double)i_ToWidth / (double)i_ToHeight)

{

i_OriginalHeight = img_OriginalImage.Height;

i_OriginalWidth = img_OriginalImage.Height * i_ToWidth / i_ToHeight;

y = 0;

x = (img_OriginalImage.Width - i_OriginalWidth) / 2;

}

else

{

i_OriginalWidth = img_OriginalImage.Width;

i_OriginalHeight = img_OriginalImage.Width * height / i_ToWidth;

x = 0;

y = (img_OriginalImage.Height - i_OriginalHeight) / 2;

}

break;

default:

break;

}

//新建一个BMP图片

System.Drawing.Image img_BitMap = new System.Drawing.Bitmap(i_ToWidth, i_ToHeight);

//新建一个画板

System.Drawing.Graphics gp = System.Drawing.Graphics.FromImage(img_BitMap);

//设置高质量插值法

gp.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;

//设置高质量、低速度呈现平滑程度

gp.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

gp.CompositingQuality = CompositingQuality.HighQuality;

//清空画布并以透明背景色填充

gp.Clear(Color.Transparent);

//指定位置并按大小绘制原图片的指定部分

gp.DrawImage(img_OriginalImage, new Rectangle(0, 0, i_ToWidth, i_ToHeight), new Rectangle(x, y, i_OriginalWidth, i_OriginalHeight), GraphicsUnit.Pixel);

try

{

EncoderParameters ep = new EncoderParameters();

long[] qy = new long[1];

qy[0] = 100;//设置压缩的比例1-100

EncoderParameter eParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qy);

ep.Param[0] = eParam;

ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();

ImageCodecInfo jpegICIinfo = null;

for (int i = 0; i < arrayICI.Length; i++)

{

if (arrayICI[i].FormatDescription.Equals("JPEG"))

{

jpegICIinfo = arrayICI[i];

break;

}

}

if (jpegICIinfo != null && Equals(tFormat, ImageFormat.Jpeg))

{

//以JPG格式保存图片

img_BitMap.Save(thumbnailPath, jpegICIinfo, ep);

//Const.iSuccessCount++;

}

else

{

img_BitMap.Save(thumbnailPath, tFormat);

//Const.iSuccessCount++;

}

}

catch (Exception ex)

{

Console.WriteLine("复制图片:" + originalImagePath + "失败！\r\n" + ex.Message + ex.StackTrace);

}

finally

{

if (img_OriginalImage != null)

{

img_OriginalImage.Dispose();

}

if (img_BitMap != null)

{

img_BitMap.Dispose();

}

if (gp != null)

{

gp.Dispose();

}

//GC.Collect();

}

}

}

}