.net等比缩放生成缩略图的方法
生成缩略图是一个十分常用功能,找到了一个方法,重写部分代码,实用又好用,.net又一个生成缩略图的方法,不变形
///<summary> ///为图片生成缩略图 ///</summary> ///<paramname="phyPath">原图片的路径</param> ///<paramname="width">缩略图宽</param> ///<paramname="height">缩略图高</param> ///<returns></returns> publicSystem.Drawing.ImageGetHvtThumbnail(System.Drawing.Imageimage,intwidth,intheight) { Bitmapm_hovertreeBmp=newBitmap(width,height); //从Bitmap创建一个System.Drawing.Graphics Graphicsm_HvtGr=Graphics.FromImage(m_hovertreeBmp); //设置 m_HvtGr.SmoothingMode=System.Drawing.Drawing2D.SmoothingMode.HighQuality; //下面这个也设成高质量 m_HvtGr.CompositingQuality=System.Drawing.Drawing2D.CompositingQuality.HighQuality; //下面这个设成High m_HvtGr.InterpolationMode=System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic; //把原始图像绘制成上面所设置宽高的缩小图 RectanglerectDestination=newRectangle(0,0,width,height); intm_width,m_height; if(image.Width*height>image.Height*width) { m_height=image.Height; m_width=(image.Height*width)/height; } else { m_width=image.Width; m_height=(image.Width*height)/width; } m_HvtGr.DrawImage(image,rectDestination,0,0,m_width,m_height,GraphicsUnit.Pixel); returnm_hovertreeBmp; }
C#缩略图生成类,采用高质量插值法实现缩略图生成,高质量,低速度呈现平滑程度,可以保持缩略图纵横比,在获取缩略图的时候一开始就根据百分比获取图片的尺寸、根据设定的大小返回图片的大小,并高质量保存缩略图图片,为原图片设置EncoderParameters对象。
以下为类文件,建议保存文件名为:ImageHelper.cs
usingSystem; usingSystem.Collections.Generic; usingSystem.Drawing; usingSystem.Drawing.Imaging; namespaceHtmlSnap { publicstaticclassImageHelper { ///获取缩略图 publicstaticImageGetThumbnailImage(Imageimage,intwidth,intheight) { if(image==null||width<1||height<1) returnnull; //新建一个bmp图片 Imagebitmap=newSystem.Drawing.Bitmap(width,height); //新建一个画板 using(Graphicsg=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,newRectangle(0,0,width,height), newRectangle(0,0,image.Width,image.Height), GraphicsUnit.Pixel); returnbitmap; } } ///<summary> ///生成缩略图,并保持纵横比 ///</summary> ///<returns>生成缩略图后对象</returns> publicstaticImageGetThumbnailImageKeepRatio(Imageimage,intwidth,intheight) { SizeimageSize=GetImageSize(image,width,height); returnGetThumbnailImage(image,imageSize.Width,imageSize.Height); } ///<summary> ///根据百分比获取图片的尺寸 ///</summary> publicstaticSizeGetImageSize(Imagepicture,intpercent) { if(picture==null||percent<1) returnSize.Empty; intwidth=picture.Width*percent/100; intheight=picture.Height*percent/100; returnGetImageSize(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> publicstaticSizeGetImageSize(Imagepicture,intwidth,intheight) { if(picture==null||width<1||height<1) returnSize.Empty; SizeimageSize; imageSize=newSize(width,height); doubleheightRatio=(double)picture.Height/picture.Width; doublewidthRatio=(double)picture.Width/picture.Height; intdesiredHeight=imageSize.Height; intdesiredWidth=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); } returnimageSize; } ///<summary> ///获取图像编码解码器的所有相关信息 ///</summary> ///<paramname="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> publicstaticImageCodecInfoGetCodecInfo(stringmimeType) { ImageCodecInfo[]CodecInfo=ImageCodecInfo.GetImageEncoders(); foreach(ImageCodecInfoiciinCodecInfo) { if(ici.MimeType==mimeType)returnici; } returnnull; } publicstaticImageCodecInfoGetImageCodecInfo(ImageFormatformat) { ImageCodecInfo[]encoders=ImageCodecInfo.GetImageEncoders(); foreach(ImageCodecInfoicfinencoders) { if(icf.FormatID==format.Guid) { returnicf; } } returnnull; } publicstaticvoidSaveImage(Imageimage,stringsavePath,ImageFormatformat) { SaveImage(image,savePath,GetImageCodecInfo(format)); } ///<summary> ///高质量保存图片 ///</summary> privatestaticvoidSaveImage(Imageimage,stringsavePath,ImageCodecInfoici) { //设置原图片对象的EncoderParameters对象 EncoderParametersparms=newEncoderParameters(1); EncoderParameterparm=newEncoderParameter(Encoder.Quality,((long)95)); parms.Param[0]=parm; image.Save(savePath,ici,parms); parms.Dispose(); } } }