我要评论本文实例讲述了c#创建缩略图操作类。分享给大家供大家参考。具体分析如下：
这个c#类可以生成各种形式的缩略图，可以自动保持图片比例缩略，可以根据百分比获得图片尺寸等
using system;
using system.collections.generic;
using system.drawing;
using system.drawing.imaging;
namespace htmlsnap
{
public static class imagehelper
{
/// <summary>
/// 获取缩略图
/// </summary>
/// <param name="image"></param>
/// <param name="width"></param>
/// <param name="height"></param>
/// <returns></returns>
public static image getthumbnailimage(image image, int width, int height)
{
if (image == null || width < 1 || height < 1)
return null;
// 新建一个bmp图片
//
image bitmap = new system.drawing.bitmap(width, height);
// 新建一个画板
//
using (graphics g = system.drawing.graphics.fromimage(bitmap))
{
// 设置高质量插值法
//
g.interpolationmode = system.drawing.drawing2d.interpolationmode.highqualitybicubic;
// 设置高质量,低速度呈现平滑程度
//
g.smoothingmode = system.drawing.drawing2d.smoothingmode.highquality;
// 高质量、低速度复合
//
g.compositingquality = system.drawing.drawing2d.compositingquality.highquality;
// 清空画布并以透明背景色填充
//
g.clear(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(image, new rectangle(0, 0, width, height),
new rectangle(0, 0, image.width, image.height),
graphicsunit.pixel);
return bitmap;
}
}
/// <summary>
/// 生成缩略图，并保持纵横比
/// </summary>
/// <param name="image"></param>
/// <param name="width"></param>
/// <param name="height"></param>
/// <returns>生成缩略图后对象</returns>
public static image getthumbnailimagekeepratio(image image, int width, int height)
{
size imagesize = getimagesize(image, width, height);
return getthumbnailimage(image, imagesize.width, imagesize.height);
}
/// <summary>
/// 根据百分比获取图片的尺寸
/// </summary>
/// <param name="picture"></param>
/// <param name="percent"></param>
/// <returns></returns>
public static size getimagesize(image picture, int percent)
{
if (picture == null || percent < 1)
return size.empty;
int width = picture.width * percent / 100;
int height = picture.height * percent / 100;
return getimagesize(picture, width, height);
}
/// <summary>
/// 根据设定的大小返回图片的大小，考虑图片长宽的比例问题
/// </summary>
/// <param name="picture"></param>
/// <param name="width"></param>
/// <param name="height"></param>
/// <returns></returns>
public static size getimagesize(image picture, int width, int height)
{
if (picture == null || width < 1 || height < 1)
return size.empty;
size imagesize;
imagesize = new size(width, height);
double heightratio = (double)picture.height / picture.width;
double widthratio = (double)picture.width / picture.height;
int desiredheight = imagesize.height;
int desiredwidth = imagesize.width;
imagesize.height = desiredheight;
if (widthratio > 0)
imagesize.width = convert.toint32(imagesize.height * widthratio);
if (imagesize.width > desiredwidth)
{
imagesize.width = desiredwidth;
imagesize.height = convert.toint32(imagesize.width * heightratio);
}
return imagesize;
}
/// <summary>
/// 获取图像编码解码器的所有相关信息
/// </summary>
/// <param name="mimetype">包含编码解码器的多用途网际邮件扩充协议 (mime) 类型的字符串</param>
/// <returns>返回图像编码解码器的所有相关信息</returns>
public static imagecodecinfo getcodecinfo(string mimetype)
{
imagecodecinfo[] codecinfo = imagecodecinfo.getimageencoders();
foreach (imagecodecinfo ici in codecinfo)
{
if (ici.mimetype == mimetype) return ici;
}
return null;
}
public static imagecodecinfo getimagecodecinfo(imageformat format)
{
imagecodecinfo[] encoders = imagecodecinfo.getimageencoders();
foreach (imagecodecinfo icf in encoders)
{
if (icf.formatid == format.guid)
{
return icf;
}
}
return null;
}
public static void saveimage(image image, string savepath, imageformat format)
{
saveimage(image, savepath, getimagecodecinfo(format));
}
/// <summary>
/// 高质量保存图片
/// </summary>
/// <param name="image"></param>
/// <param name="savepath"></param>
/// <param name="ici"></param>
private static void saveimage(image image, string savepath, imagecodecinfo ici)
{
// 设置 原图片 对象的 encoderparameters 对象
//
encoderparameters parms = new encoderparameters(1);
encoderparameter parm = new encoderparameter(encoder.quality, ((long)95));
parms.param[0] = parm;
image.save(savepath, ici, parms);
parms.dispose();
}
}
}
希望本文所述对大家的c#程序设计有所帮助。
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