c# 图片无损缩放类

来自：http://hi.baidu.com/luli327/blog/item/541c808038a8ebd49123d993.html

 

2007-12-10 11:03/******************************************************************** * * 软件项目名称: draw* 创建者: luli327* 创建时间: 2007年12月9日 * 说明: * 一个图片缩放的类* ********************************************************************/ using System;using System.IO;using System.Drawing;using System.Drawing.Imaging;using System.Drawing.Drawing2D;namespace ZHT.Utility.Share{public class Thumbnail{ public Thumbnail() { } /// <SUMMARY> /// 图片缩放 /// </SUMMARY> /// <PARAM name="sourceFile">图片源路径</PARAM> /// <PARAM name="destFile">缩放后图片输出路径</PARAM> /// <PARAM name="destHeight">缩放后图片高度</PARAM> /// <PARAM name="destWidth">缩放后图片宽度</PARAM> /// <RETURNS></RETURNS> public static bool GetThumbnail(string sourceFile, string destFile, int destHeight, int destWidth) { System.Drawing.Image imgSource = System.Drawing.Image.FromFile(sourceFile); System.Drawing.Imaging.ImageFormat thisFormat = imgSource.RawFormat; int sW = 0, sH = 0; // 按比例缩放 int sWidth = imgSource.Width; int sHeight = imgSource.Height; if(sHeight>destHeight || sWidth>destWidth) { if((sWidth*destHeight)>(sHeight*destWidth)) { sW = destWidth; sH = (destWidth*sHeight)/sWidth; } else { sH = destHeight; sW = (sWidth*destHeight)/sHeight; } } else { sW = sWidth; sH = sHeight; } Bitmap outBmp = new Bitmap(destWidth, destHeight); Graphics g = Graphics.FromImage(outBmp); g.Clear(Color.WhiteSmoke); // 设置画布的描绘质量 g.CompositingQuality = CompositingQuality.HighQuality; g.SmoothingMode = SmoothingMode.HighQuality; g.InterpolationMode = InterpolationMode.HighQualityBicubic; g.DrawImage(imgSource, new Rectangle((destWidth-sW)/2,(destHeight-sH)/2, sW, sH),0,0, imgSource.Width, imgSource.Height, GraphicsUnit.Pixel); g.Dispose(); // 以下代码为保存图片时，设置压缩质量 EncoderParameters encoderParams = new EncoderParameters(); long[] quality = new long[1]; quality[0] = 100; EncoderParameter encoderParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, quality); encoderParams.Param[0] = encoderParam; try { //获得包含有关内置图像编码解码器的信息的ImageCodecInfo 对象。 ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders(); ImageCodecInfo jpegICI = null; for (int x = 0; x < arrayICI.Length; x++) { if (arrayICI[x].FormatDescription.Equals("JPEG")) { jpegICI = arrayICI[x];//设置JPEG编码 break; } } if (jpegICI != null) { outBmp.Save(destFile, jpegICI, encoderParams); } else { outBmp.Save(destFile, thisFormat); } return true; } catch { return false; } finally { imgSource.Dispose(); outBmp.Dispose(); } }}}