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c#生成图片缩略图的类(2种实现思路)

c#思路 实现 图片 生成 缩略图
2023-06-13 09:15:00 时间
第一种
复制代码代码如下:

/**////<summary>
///生成缩略图
///</summary>
///<paramname="originalImagePath">源图路径（物理路径）</param>
///<paramname="thumbnailPath">缩略图路径（物理路径）</param>
///<paramname="width">缩略图宽度</param>
///<paramname="height">缩略图高度</param>
///<paramname="mode">生成缩略图的方式</param>
publicstaticvoidMakeThumbnail(stringoriginalImagePath,stringthumbnailPath,intwidth,intheight,stringmode)
{
ImageoriginalImage=Image.FromFile(originalImagePath);
inttowidth=width;
inttoheight=height;
intx=0;
inty=0;
intow=originalImage.Width;
intoh=originalImage.Height;
switch(mode)
{
case"HW"://指定高宽缩放（可能变形）
break;
case"W"://指定宽，高按比例
toheight=originalImage.Height*width/originalImage.Width;
break;
case"H"://指定高，宽按比例
towidth=originalImage.Width*height/originalImage.Height;
break;
case"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
Imagebitmap=newSystem.Drawing.Bitmap(towidth,toheight);
//新建一个画板
Graphicsg=System.Drawing.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(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,newRectangle(0,0,towidth,toheight),
newRectangle(x,y,ow,oh),
GraphicsUnit.Pixel);
try
{
//以jpg格式保存缩略图
bitmap.Save(thumbnailPath,System.Drawing.Imaging.ImageFormat.Jpeg);
}
catch(System.Exceptione)
{
throwe;
}
finally
{
originalImage.Dispose();
bitmap.Dispose();
g.Dispose();
}
}

关键方法Graphics.DrawImage见ms-help://MS.NETFrameworkSDKv1.1.CHS/cpref/html/frlrfsystemdrawinggraphicsclassdrawimagetopic11.htm
第二种
4个重载方法,有直接返回Image对象的,有生成缩略图,并且保存到指定目录的!
复制代码代码如下:

usingSystem.IO;
usingSystem.Drawing;
usingSystem.Drawing.Imaging;
///<summary>
///图片处理类
///1、生成缩略图片或按照比例改变图片的大小和画质
///2、将生成的缩略图放到指定的目录下
///</summary>
publicclassImageClass
{
publicImageResourceImage;
privateintImageWidth;
privateintImageHeight;
publicstringErrMessage;
///<summary>
///类的构造函数
///</summary>
///<paramname="ImageFileName">图片文件的全路径名称</param>
publicImageClass(stringImageFileName)
{
ResourceImage=Image.FromFile(ImageFileName);
ErrMessage="";
}
publicboolThumbnailCallback()
{
returnfalse;
}
///<summary>
///生成缩略图重载方法1，返回缩略图的Image对象
///</summary>
///<paramname="Width">缩略图的宽度</param>
///<paramname="Height">缩略图的高度</param>
///<returns>缩略图的Image对象</returns>
publicImageGetReducedImage(intWidth,intHeight)
{
try
{
ImageReducedImage;
Image.GetThumbnailImageAbortcallb=newImage.GetThumbnailImageAbort(ThumbnailCallback);
ReducedImage=ResourceImage.GetThumbnailImage(Width,Height,callb,IntPtr.Zero);
returnReducedImage;
}
catch(Exceptione)
{
ErrMessage=e.Message;
returnnull;
}
}
///<summary>
///生成缩略图重载方法2，将缩略图文件保存到指定的路径
///</summary>
///<paramname="Width">缩略图的宽度</param>
///<paramname="Height">缩略图的高度</param>
///<paramname="targetFilePath">缩略图保存的全文件名，(带路径)，参数格式：D:Imagesilename.jpg</param>
///<returns>成功返回true，否则返回false</returns>
publicboolGetReducedImage(intWidth,intHeight,stringtargetFilePath)
{
try
{
ImageReducedImage;
Image.GetThumbnailImageAbortcallb=newImage.GetThumbnailImageAbort(ThumbnailCallback);
ReducedImage=ResourceImage.GetThumbnailImage(Width,Height,callb,IntPtr.Zero);
ReducedImage.Save(@targetFilePath,ImageFormat.Jpeg);
ReducedImage.Dispose();
returntrue;
}
catch(Exceptione)
{
ErrMessage=e.Message;
returnfalse;
}
}
///<summary>
///生成缩略图重载方法3，返回缩略图的Image对象
///</summary>
///<paramname="Percent">缩略图的宽度百分比如：需要百分之80，就填0.8</param>
///<returns>缩略图的Image对象</returns>
publicImageGetReducedImage(doublePercent)
{
try
{
ImageReducedImage;
Image.GetThumbnailImageAbortcallb=newImage.GetThumbnailImageAbort(ThumbnailCallback);
ImageWidth=Convert.ToInt32(ResourceImage.Width*Percent);
ImageHeight=Convert.ToInt32(ResourceImage.Width*Percent);
ReducedImage=ResourceImage.GetThumbnailImage(ImageWidth,ImageHeight,callb,IntPtr.Zero);
returnReducedImage;
}
catch(Exceptione)
{
ErrMessage=e.Message;
returnnull;
}
}
///<summary>
///生成缩略图重载方法4，返回缩略图的Image对象
///</summary>
///<paramname="Percent">缩略图的宽度百分比如：需要百分之80，就填0.8</param>
///<paramname="targetFilePath">缩略图保存的全文件名，(带路径)，参数格式：D:Imagesilename.jpg</param>
///<returns>成功返回true,否则返回false</returns>
publicboolGetReducedImage(doublePercent,stringtargetFilePath)
{
try
{
ImageReducedImage;
Image.GetThumbnailImageAbortcallb=newImage.GetThumbnailImageAbort(ThumbnailCallback);
ImageWidth=Convert.ToInt32(ResourceImage.Width*Percent);
ImageHeight=Convert.ToInt32(ResourceImage.Width*Percent);
ReducedImage=ResourceImage.GetThumbnailImage(ImageWidth,ImageHeight,callb,IntPtr.Zero);
ReducedImage.Save(@targetFilePath,ImageFormat.Jpeg);
ReducedImage.Dispose();
returntrue;
}
catch(Exceptione)
{
ErrMessage=e.Message;
returnfalse;
}
}
}

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