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();
}
}
}
}