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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：
我要评论 /// <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：原文转载自。
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