【转载】C#生成图片的缩略图
作者：互联网
图片处理是C#程序开发中时常会涉及到的一个业务，除了图像的上传、保存以及下载等功能外，根据上传的图片生成一个缩略图也是常见业务，在C#语言中，可以通过Image类提供的相关方法对图片进行操作，如指定宽高对图片进行缩放， 指定高宽裁减裁剪图片、生成图片水印等。
定义一个图片处理工具类PicDeal，该类实现了生成缩略图、在图片上生成图片水印等相应功能。具体的业务代码如下：
/// <summary>
/// 枚举,生成缩略图模式
/// </summary>
public enum ThumbnailMod : byte
{
/// <summary>
/// HW
/// </summary>
HW,
/// <summary>
/// W
/// </summary>
W,
/// <summary>
/// H
/// </summary>
H,
/// <summary>
/// Cut
/// </summary>
Cut
};
/// <summary>
/// 操作图片类, 生成缩略图,添加水印
/// </summary>
public static class PicDeal
{
private static Hashtable htmimes = new Hashtable();
internal static readonly string AllowExt = ".jpe|.jpeg|.jpg|.png|.tif|.tiff|.bmp";
#region 生成缩略图
/// <summary>
/// 生成缩略图
/// </summary>
/// <param name="originalImagePath"></param>
/// <param name="width"></param>
/// <param name="height"></param>
/// <param name="mode"></param>
/// <returns></returns>
public static bool MakeThumbnail(string originalImagePath, int width, int height, ThumbnailMod mode)
{
string thumbnailPath = originalImagePath.Substring(0, originalImagePath.LastIndexOf('.')) + "s.jpg";
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 ThumbnailMod.HW://指定高宽缩放（可能变形）
break;
case ThumbnailMod.W://指定宽，高按比例
toheight = originalImage.Height * width / originalImage.Width;
break;
case ThumbnailMod.H://指定高，宽按比例
towidth = originalImage.Width * height / originalImage.Height;
break;
case ThumbnailMod.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
Image bitmap = new Bitmap(towidth, toheight);
//新建一个画板
Graphics g = 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(System.Drawing.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);
bool isok = false;
try
{
//以jpg格式保存缩略图
bitmap.Save(thumbnailPath, ImageFormat.Jpeg);
isok = true;
}
catch (Exception)
{
thumbnailPath = originalImagePath;
}
finally
{
originalImage.Dispose();
bitmap.Dispose();
g.Dispose();
}
return isok;
}
#endregion
#region 在图片上生成图片水印
///// <summary>
///// 在图片上生成图片水印
///// </summary>
///// <param name="Path">原服务器图片路径</param>
///// <param name="Path_syp">生成的带图片水印的图片路径</param>
///// <param name="Path_sypf">水印图片路径</param>
/// <summary>
/// 在图片上生成图片水印
/// </summary>
/// <param name="Path">原服务器图片路径</param>
/// <param name="Path_sypf">水印图片路径</param>
public static void AddWaterPic(string Path, string Path_sypf)
{
try
{
Image image = Image.FromFile(Path);
Image copyImage = Image.FromFile(Path_sypf);
Graphics g = Graphics.FromImage(image);
g.DrawImage(copyImage, new System.Drawing.Rectangle(image.Width - copyImage.Width, image.Height - copyImage.Height, copyImage.Width, copyImage.Height), 0, 0, copyImage.Width, copyImage.Height, System.Drawing.GraphicsUnit.Pixel);
g.Dispose();
image.Save(Path + ".temp");
image.Dispose();
System.IO.File.Delete(Path);
File.Move(Path + ".temp", Path);
}
catch
{ }
}
#endregion
/// <summary>
/// 公共方法
/// </summary>
private static void GetImgType()
{
htmimes[".jpe"] = "image/jpeg";
htmimes[".jpeg"] = "image/jpeg";
htmimes[".jpg"] = "image/jpeg";
htmimes[".png"] = "image/png";
htmimes[".tif"] = "image/tiff";
htmimes[".tiff"] = "image/tiff";
htmimes[".bmp"] = "image/bmp";
}
#region 返回新图片尺寸
/// <summary>
/// 返回新图片尺寸
/// </summary>
/// <param name="width">原始宽</param>
/// <param name="height">原始高</param>
/// <param name="maxWidth">新图片最大宽</param>
/// <param name="maxHeight">新图片最大高</param>
/// <returns></returns>
public static Size ResizeImage(int width, int height, int maxWidth, int maxHeight)
{
decimal MAX_WIDTH = (decimal)maxWidth;
decimal MAX_HEIGHT = (decimal)maxHeight;
decimal ASPECT_RATIO = MAX_WIDTH / MAX_HEIGHT;
int newWidth, newHeight;
decimal originalWidth = (decimal)width;
decimal originalHeight = (decimal)height;
if (originalWidth > MAX_WIDTH || originalHeight > MAX_HEIGHT)
{
decimal factor;
// determine the largest factor
if (originalWidth / originalHeight > ASPECT_RATIO)
{
factor = originalWidth / MAX_WIDTH;
newWidth = Convert.ToInt32(originalWidth / factor);
newHeight = Convert.ToInt32(originalHeight / factor);
}
else
{
factor = originalHeight / MAX_HEIGHT;
newWidth = Convert.ToInt32(originalWidth / factor);
newHeight = Convert.ToInt32(originalHeight / factor);
}
}
else
{
newWidth = width;
newHeight = height;
}
return new Size(newWidth, newHeight);
}
#endregion
}
备注：此文章转载自C#生成图片的缩略图_IT技术小趣屋。
标签：originalImage,Width,缩略图,C#,image,Height,int,转载,图片 来源： https://www.cnblogs.com/xu-yi/p/10525125.html