转载来自：http://write.blog.csdn.net/postedit/7715729
一、测试代码
private void button1_Click(object sender, EventArgs e)
{
string newSourcePath = ImgPath;//源图存放目录
string newNewDir = MakePath; //新图存放目录
string sourceFile = Path.Combine(ImgPath, "app1.jpg"); //获取原图路径
string newFile = string.Empty; //新图路径
ImgThumbnail iz = new ImgThumbnail();
Action<ImgThumbnail.ImgThumbnailType> Thumbnail = (type =>
{
//生成质量
for (int i = 100; i >= 10; i -= 10)
{
//计算新图路径，测试命名：原图名_new_缩放类型_压缩质量.jpg
newFile = Path.Combine(newNewDir, string.Format("app1_new_{1}_{0}.jpg", i, type.ToString()));
//压缩图片
iz.Thumbnail(sourceFile, newFile, 100, 100, i, type);
}
});
Thumbnail(ImgThumbnail.ImgThumbnailType.Cut);//裁剪压缩（裁剪压缩还不好用，待调整！）
Thumbnail(ImgThumbnail.ImgThumbnailType.H); //以高度为参照压缩，不变形
Thumbnail(ImgThumbnail.ImgThumbnailType.W); //以宽度为参照压缩，不变形
Thumbnail(ImgThumbnail.ImgThumbnailType.WH); //固定宽高压缩，变形
MessageBox.Show("完成");
}
二、操作类
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
namespace MagickNet.App
{
/// <summary>
/// 图片压缩
/// </summary>
public class ImgThumbnail
{
#region 枚举
/// <summary>
/// 指定缩放类型
/// </summary>
public enum ImgThumbnailType
{
/// <summary>
/// 无
/// </summary>
Nothing=0,
/// <summary>
/// 指定高宽缩放（可能变形）
/// </summary>
WH = 1,
/// <summary>
/// 指定宽，高按比例
/// </summary>
W = 2,
/// <summary>
/// 指定高，宽按比例
/// </summary>
H = 3,
/// <summary>
/// 指定高宽裁减（不变形）
/// </summary>
Cut = 4,
/// <summary>
/// 按照宽度成比例缩放后，按照指定的高度进行裁剪
/// </summary>
W_HCut = 5,
}
#endregion
#region Thumbnail
/// <summary>
/// 无损压缩图片
/// </summary>
/// <param name="sourceFile">原图片</param>
/// <param name="stream">压缩后保存到流中</param>
/// <param name="height">高度</param>
/// <param name="width"></param>
/// <param name="quality">压缩质量 1-100</param>
/// <param name="type">压缩缩放类型</param>
/// <returns></returns>
private static Bitmap Thumbnail(string sourceFile, int width, int height, int quality
, ImgThumbnailType type, out ImageFormat tFormat)
{
using (System.Drawing.Image iSource = System.Drawing.Image.FromFile(sourceFile))
{
tFormat = iSource.RawFormat;
//缩放后的宽度和高度
int toWidth = width;
int toHeight = height;
//
int x = 0;
int y = 0;
int oWidth = iSource.Width;
int oHeight = iSource.Height;
switch (type)
{
case ImgThumbnailType.WH://指定高宽缩放（可能变形）
{
break;
}
case ImgThumbnailType.W://指定宽，高按比例
{
toHeight = iSource.Height * width / iSource.Width;
break;
}
case ImgThumbnailType.H://指定高，宽按比例
{
toWidth = iSource.Width * height / iSource.Height;
break;
}
case ImgThumbnailType.Cut://指定高宽裁减（不变形）
{
if ((double)iSource.Width / (double)iSource.Height > (double)toWidth / (double)toHeight)
{
oHeight = iSource.Height;
oWidth = iSource.Height * toWidth / toHeight;
y = 0;
x = (iSource.Width - oWidth) / 2;
}
else
{
oWidth = iSource.Width;
oHeight = iSource.Width * height / toWidth;
x = 0;
y = (iSource.Height - oHeight) / 2;
}
break;
}
case ImgThumbnailType.W_HCut://按照宽度成比例缩放后，按照指定的高度进行裁剪
{
toHeight = iSource.Height * width / iSource.Width;
if (height < toHeight)
{
oHeight = oHeight * height / toHeight;
toHeight = toHeight * height / toHeight;
}
break;
}
default:
break;
}
Bitmap ob = new Bitmap(toWidth, toHeight);
//ImgWaterMark iwm = new ImgWaterMark();
//iwm.AddWaterMark(ob, towidth, toheight, "www.****.com");
Graphics g = Graphics.FromImage(ob);
g.Clear(System.Drawing.Color.WhiteSmoke);
g.CompositingQuality = CompositingQuality.HighQuality;
g.SmoothingMode = SmoothingMode.HighQuality;
g.InterpolationMode = InterpolationMode.HighQualityBicubic;
g.DrawImage(iSource
, new Rectangle(x, y, toWidth, toHeight)
, new Rectangle(0, 0, oWidth, oHeight)
, GraphicsUnit.Pixel);
g.Dispose();
return ob;
}
}
#endregion
}
}
转载请保留：http://write.blog.csdn.net/postedit/7715729
C# 无损图片压缩—— 基于Framework.40 类库实现