雷鬼头怎么编:C#图片处理高级应用(裁剪,缩放,清晰度,水印222) - 吴剑-WEB应用 - 博客园

C#图片处理高级应用(裁剪,缩放,清晰度,水印)

吴剑

http://wu-jian.cnblogs.com/

前言

需求源自项目中的一些应用，比如相册功能，通常用户上传相片后我们都会针对该相片再生成一张缩略图，用于其它页面上的列表显示。随便看一下，大部分网站基本都是将原图等比缩放来生成缩略图。但完美主义者会发现一些问题，比如显示排版时想让相片缩略图列表非常统一、整齐、和美观，比如要求每张缩略图大小固定为120 x90且不拉伸变形怎么办？再比如用户头像如何让缩略图比原图更清晰？或是如何在上传的图片下加一个半透明的LOGO水印？

OK，本文根据自己的项目代码描述以上问题的解决方案，所谓C#图片处理高级应用，感觉有点标题党了，这些功能并无多大技术含量。全部基于.Net Framework类库完成，代码中包含了C#图片处理的一些基础知识，与大家分享，个人能力有限，不足之处还请及时指正。

提高缩略图清晰度

(原图200*200,12.3k)(处理后80*80,17.7k)

之前一直认为缩略图不可能比原图清晰，直到某天一位产品的同事给我看某网站的效果。于是开始寻找.NET下实现代码，仔细观察缩略图确实比原图更清晰了一些，但代价是缩略图文件比原图更大，所以如果你想让一张占满显示器屏幕的超大图片更清晰，那么图片占用空间和网络流量就必需考虑了，如果是互联网应用，建议缩略图在200像素以内的使用该方法。当然如果哪位有更好的代码即能让图片文件大小变化不大又让图片更清晰还请分享。

图片裁剪

(原图256*192)(裁剪要求100*100)

(原图256*192)(裁剪要求90*120)

(原图256*192)(裁剪要求120*90)

(原图146*256)(裁剪要求90*120)

(原图146*256)(裁剪要求120*90)

算法：以原图中心作为裁剪中心，最大范围的对原图进行裁剪，然后对裁剪结果等比缩放。

图片水印

仅演示了效果，如需要变更字体、水印透明度、位置等可自行在代码或方法中扩展。

代码

封装了几个通用的方法，如发现有BUG或漏洞还请及时指正。

using System;using System.Collections.Generic;using System.Text;using System.IO;using System.Drawing;using System.Drawing.Drawing2D;using System.Drawing.Imaging;namespace WuJian.Common{/// 
/// 图片处理类/// 吴剑 2008-07-02 创建/// 吴剑 2011-01-21 修改/// 
public class PTImage{#region 正方型裁剪并缩放/// 
/// 正方型裁剪/// 以图片中心为轴心，截取正方型，然后等比缩放/// 用于头像处理/// 
/// 吴剑 2010-11-23/// 原图HttpPostedFile对象/// 缩略图存放地址/// 指定的边长（正方型）/// 质量（范围0-100）public static void CutForSquare(System.Web.HttpPostedFile postedFile, string fileSaveUrl, int side, int quality){//创建目录string dir = Path.GetDirectoryName(fileSaveUrl);if (!Directory.Exists(dir))Directory.CreateDirectory(dir);//原始图片（获取原始图片创建对象，并使用流中嵌入的颜色管理信息）System.Drawing.Image initImage = System.Drawing.Image.FromStream(postedFile.InputStream, true);//原图宽高均小于模版，不作处理，直接保存if (initImage.Width <= side && initImage.Height <= side){initImage.Save(fileSaveUrl, System.Drawing.Imaging.ImageFormat.Jpeg);}else{//原始图片的宽、高int initWidth = initImage.Width;int initHeight = initImage.Height;//非正方型先裁剪为正方型if (initWidth != initHeight){//截图对象System.Drawing.Image pickedImage = null;System.Drawing.Graphics pickedG = null;//宽大于高的横图if (initWidth > initHeight){//对象实例化pickedImage = new System.Drawing.Bitmap(initHeight, initHeight);pickedG = System.Drawing.Graphics.FromImage(pickedImage);//设置质量pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;//定位Rectangle fromR = new Rectangle((initWidth - initHeight) / 2, 0, initHeight, initHeight);Rectangle toR = new Rectangle(0, 0, initHeight, initHeight);//画图pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel);//重置宽initWidth = initHeight;}//高大于宽的竖图else{//对象实例化pickedImage = new System.Drawing.Bitmap(initWidth, initWidth);pickedG = System.Drawing.Graphics.FromImage(pickedImage);//设置质量pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;//定位Rectangle fromR = new Rectangle(0, (initHeight - initWidth) / 2, initWidth, initWidth);Rectangle toR = new Rectangle(0, 0, initWidth, initWidth);//画图pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel);//重置高initHeight = initWidth;}//将截图对象赋给原图initImage = (System.Drawing.Image)pickedImage.Clone();//释放截图资源pickedG.Dispose();pickedImage.Dispose();}//缩略图对象System.Drawing.Image resultImage = new System.Drawing.Bitmap(side, side);System.Drawing.Graphics resultG = System.Drawing.Graphics.FromImage(resultImage);//设置质量resultG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;resultG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;//用指定背景色清空画布resultG.Clear(Color.White);//绘制缩略图resultG.DrawImage(initImage, new System.Drawing.Rectangle(0, 0, side, side), new System.Drawing.Rectangle(0, 0, initWidth, initHeight), System.Drawing.GraphicsUnit.Pixel);//关键质量控制//获取系统编码类型数组,包含了jpeg,bmp,png,gif,tiffImageCodecInfo[] icis = ImageCodecInfo.GetImageEncoders();ImageCodecInfo ici = null;foreach (ImageCodecInfo i in icis){if (i.MimeType == "image/jpeg" || i.MimeType == "image/bmp" || i.MimeType == "image/png" || i.MimeType == "image/gif"){ici = i;}}EncoderParameters ep = new EncoderParameters(1);ep.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, (long)quality);//保存缩略图resultImage.Save(fileSaveUrl, ici, ep);//释放关键质量控制所用资源ep.Dispose();//释放缩略图资源resultG.Dispose();resultImage.Dispose();//释放原始图片资源initImage.Dispose();}}/// 
/// 正方型裁剪/// 以图片中心为轴心，截取正方型，然后等比缩放/// 用于头像处理/// 
/// 吴剑 2010-11-23/// 原图HttpPostedFile对象/// 缩略图存放地址/// 指定的边长（正方型）/// 质量（范围0-100）public static void CutForSquare(System.IO.Stream fromFile, string fileSaveUrl, int side, int quality){//创建目录string dir = Path.GetDirectoryName(fileSaveUrl);if (!Directory.Exists(dir))Directory.CreateDirectory(dir);//原始图片（获取原始图片创建对象，并使用流中嵌入的颜色管理信息）System.Drawing.Image initImage = System.Drawing.Image.FromStream(fromFile, true);//原图宽高均小于模版，不作处理，直接保存if (initImage.Width <= side && initImage.Height <= side){initImage.Save(fileSaveUrl, System.Drawing.Imaging.ImageFormat.Jpeg);}else{//原始图片的宽、高int initWidth = initImage.Width;int initHeight = initImage.Height;//非正方型先裁剪为正方型if (initWidth != initHeight){//截图对象System.Drawing.Image pickedImage = null;System.Drawing.Graphics pickedG = null;//宽大于高的横图if (initWidth > initHeight){//对象实例化pickedImage = new System.Drawing.Bitmap(initHeight, initHeight);pickedG = System.Drawing.Graphics.FromImage(pickedImage);//设置质量pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;//定位Rectangle fromR = new Rectangle((initWidth - initHeight) / 2, 0, initHeight, initHeight);Rectangle toR = new Rectangle(0, 0, initHeight, initHeight);//画图pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel);//重置宽initWidth = initHeight;}//高大于宽的竖图else{//对象实例化pickedImage = new System.Drawing.Bitmap(initWidth, initWidth);pickedG = System.Drawing.Graphics.FromImage(pickedImage);//设置质量pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;//定位Rectangle fromR = new Rectangle(0, (initHeight - initWidth) / 2, initWidth, initWidth);Rectangle toR = new Rectangle(0, 0, initWidth, initWidth);//画图pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel);//重置高initHeight = initWidth;}//将截图对象赋给原图initImage = (System.Drawing.Image)pickedImage.Clone();//释放截图资源pickedG.Dispose();pickedImage.Dispose();}//缩略图对象System.Drawing.Image resultImage = new System.Drawing.Bitmap(side, side);System.Drawing.Graphics resultG = System.Drawing.Graphics.FromImage(resultImage);//设置质量resultG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;resultG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;//用指定背景色清空画布resultG.Clear(Color.White);//绘制缩略图resultG.DrawImage(initImage, new System.Drawing.Rectangle(0, 0, side, side), new System.Drawing.Rectangle(0, 0, initWidth, initHeight), System.Drawing.GraphicsUnit.Pixel);//关键质量控制//获取系统编码类型数组,包含了jpeg,bmp,png,gif,tiffImageCodecInfo[] icis = ImageCodecInfo.GetImageEncoders();ImageCodecInfo ici = null;foreach (ImageCodecInfo i in icis){if (i.MimeType == "image/jpeg" || i.MimeType == "image/bmp" || i.MimeType == "image/png" || i.MimeType == "image/gif"){ici = i;}}EncoderParameters ep = new EncoderParameters(1);ep.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, (long)quality);//保存缩略图resultImage.Save(fileSaveUrl, ici, ep);//释放关键质量控制所用资源ep.Dispose();//释放缩略图资源resultG.Dispose();resultImage.Dispose();//释放原始图片资源initImage.Dispose();}}#endregion#region 固定模版裁剪并缩放/// 
/// 指定长宽裁剪/// 按模版比例最大范围的裁剪图片并缩放至模版尺寸/// 
/// 吴剑 2010-11-15/// 原图HttpPostedFile对象/// 保存路径/// 最大宽(单位:px)/// 最大高(单位:px)/// 质量（范围0-100）public static void CutForCustom(System.Web.HttpPostedFile postedFile, string fileSaveUrl, int maxWidth, int maxHeight, int quality){//从文件获取原始图片，并使用流中嵌入的颜色管理信息System.Drawing.Image initImage = System.Drawing.Image.FromStream(postedFile.InputStream, true);//原图宽高均小于模版，不作处理，直接保存if (initImage.Width <= maxWidth && initImage.Height <= maxHeight){initImage.Save(fileSaveUrl, System.Drawing.Imaging.ImageFormat.Jpeg);}else{//模版的宽高比例double templateRate = (double)maxWidth / maxHeight;//原图片的宽高比例double initRate = (double)initImage.Width / initImage.Height;//原图与模版比例相等，直接缩放if (templateRate == initRate){//按模版大小生成最终图片System.Drawing.Image templateImage = new System.Drawing.Bitmap(maxWidth, maxHeight);System.Drawing.Graphics templateG = System.Drawing.Graphics.FromImage(templateImage);templateG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;templateG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;templateG.Clear(Color.White);templateG.DrawImage(initImage, new System.Drawing.Rectangle(0, 0, maxWidth, maxHeight), new System.Drawing.Rectangle(0, 0, initImage.Width, initImage.Height), System.Drawing.GraphicsUnit.Pixel);templateImage.Save(fileSaveUrl, System.Drawing.Imaging.ImageFormat.Jpeg);}//原图与模版比例不等，裁剪后缩放else{//裁剪对象System.Drawing.Image pickedImage = null;System.Drawing.Graphics pickedG = null;//定位Rectangle fromR = new Rectangle(0, 0, 0, 0);//原图裁剪定位Rectangle toR = new Rectangle(0, 0, 0, 0);//目标定位//宽为标准进行裁剪if (templateRate > initRate){//裁剪对象实例化pickedImage = new System.Drawing.Bitmap(initImage.Width, (int)Math.Floor(initImage.Width / templateRate));pickedG = System.Drawing.Graphics.FromImage(pickedImage);//裁剪源定位fromR.X = 0;fromR.Y = (int)Math.Floor((initImage.Height - initImage.Width / templateRate) / 2);fromR.Width = initImage.Width;fromR.Height = (int)Math.Floor(initImage.Width / templateRate);//裁剪目标定位toR.X = 0;toR.Y = 0;toR.Width = initImage.Width;toR.Height = (int)Math.Floor(initImage.Width / templateRate);}//高为标准进行裁剪else{pickedImage = new System.Drawing.Bitmap((int)Math.Floor(initImage.Height * templateRate), initImage.Height);pickedG = System.Drawing.Graphics.FromImage(pickedImage);fromR.X = (int)Math.Floor((initImage.Width - initImage.Height * templateRate) / 2);fromR.Y = 0;fromR.Width = (int)Math.Floor(initImage.Height * templateRate);fromR.Height = initImage.Height;toR.X = 0;toR.Y = 0;toR.Width = (int)Math.Floor(initImage.Height * templateRate);toR.Height = initImage.Height;}//设置质量pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;//裁剪pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel);//按模版大小生成最终图片System.Drawing.Image templateImage = new System.Drawing.Bitmap(maxWidth, maxHeight);System.Drawing.Graphics templateG = System.Drawing.Graphics.FromImage(templateImage);templateG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;templateG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;templateG.Clear(Color.White);templateG.DrawImage(pickedImage, new System.Drawing.Rectangle(0, 0, maxWidth, maxHeight), new System.Drawing.Rectangle(0, 0, pickedImage.Width, pickedImage.Height), System.Drawing.GraphicsUnit.Pixel);//关键质量控制//获取系统编码类型数组,包含了jpeg,bmp,png,gif,tiffImageCodecInfo[] icis = ImageCodecInfo.GetImageEncoders();ImageCodecInfo ici = null;foreach (ImageCodecInfo i in icis){if (i.MimeType == "image/jpeg" || i.MimeType == "image/bmp" || i.MimeType == "image/png" || i.MimeType == "image/gif"){ici = i;}}EncoderParameters ep = new EncoderParameters(1);ep.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, (long)quality);//保存缩略图templateImage.Save(fileSaveUrl, ici, ep);//templateImage.Save(fileSaveUrl, System.Drawing.Imaging.ImageFormat.Jpeg);//释放资源templateG.Dispose();templateImage.Dispose();pickedG.Dispose();pickedImage.Dispose();}}//释放资源initImage.Dispose();}#endregion#region 等比缩放/// 
/// 图片等比缩放/// 
/// 吴剑 2011-01-21/// 原图HttpPostedFile对象/// 缩略图存放地址/// 指定的最大宽度/// 指定的最大高度/// 水印文字(为""表示不使用水印)/// 水印图片路径(为""表示不使用水印)public static void ZoomAuto(System.Web.HttpPostedFile postedFile, string savePath, System.Double targetWidth, System.Double targetHeight, string watermarkText, string watermarkImage){//创建目录string dir = Path.GetDirectoryName(savePath);if (!Directory.Exists(dir))Directory.CreateDirectory(dir);//原始图片（获取原始图片创建对象，并使用流中嵌入的颜色管理信息）System.Drawing.Image initImage = System.Drawing.Image.FromStream(postedFile.InputStream, true);//原图宽高均小于模版，不作处理，直接保存if (initImage.Width <= targetWidth && initImage.Height <= targetHeight){//文字水印if (watermarkText != ""){using (System.Drawing.Graphics gWater = System.Drawing.Graphics.FromImage(initImage)){System.Drawing.Font fontWater = new Font("黑体", 10);System.Drawing.Brush brushWater = new SolidBrush(Color.White);gWater.DrawString(watermarkText, fontWater, brushWater, 10, 10);gWater.Dispose();}}//透明图片水印if (watermarkImage != ""){if (File.Exists(watermarkImage)){//获取水印图片using (System.Drawing.Image wrImage = System.Drawing.Image.FromFile(watermarkImage)){//水印绘制条件：原始图片宽高均大于或等于水印图片if (initImage.Width >= wrImage.Width && initImage.Height >= wrImage.Height){Graphics gWater = Graphics.FromImage(initImage);//透明属性ImageAttributes imgAttributes = new ImageAttributes();ColorMap colorMap = new ColorMap();colorMap.OldColor = Color.FromArgb(255, 0, 255, 0);colorMap.NewColor = Color.FromArgb(0, 0, 0, 0);ColorMap[] remapTable = { colorMap };imgAttributes.SetRemapTable(remapTable, ColorAdjustType.Bitmap);float[][] colorMatrixElements = {new float[] {1.0f,  0.0f,  0.0f,  0.0f, 0.0f},new float[] {0.0f,  1.0f,  0.0f,  0.0f, 0.0f},new float[] {0.0f,  0.0f,  1.0f,  0.0f, 0.0f},new float[] {0.0f,  0.0f,  0.0f,  0.5f, 0.0f},//透明度:0.5new float[] {0.0f,  0.0f,  0.0f,  0.0f, 1.0f}};ColorMatrix wmColorMatrix = new ColorMatrix(colorMatrixElements);imgAttributes.SetColorMatrix(wmColorMatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);gWater.DrawImage(wrImage, new Rectangle(initImage.Width - wrImage.Width, initImage.Height - wrImage.Height, wrImage.Width, wrImage.Height), 0, 0, wrImage.Width, wrImage.Height, GraphicsUnit.Pixel, imgAttributes);gWater.Dispose();}wrImage.Dispose();}}}//保存initImage.Save(savePath, System.Drawing.Imaging.ImageFormat.Jpeg);}else{//缩略图宽、高计算double newWidth = initImage.Width;double newHeight = initImage.Height;//宽大于高或宽等于高（横图或正方）if (initImage.Width > initImage.Height || initImage.Width == initImage.Height){//如果宽大于模版if (initImage.Width > targetWidth){//宽按模版，高按比例缩放newWidth = targetWidth;newHeight = initImage.Height * (targetWidth / initImage.Width);}}//高大于宽（竖图）else{//如果高大于模版if (initImage.Height > targetHeight){//高按模版，宽按比例缩放newHeight = targetHeight;newWidth = initImage.Width * (targetHeight / initImage.Height);}}//生成新图//新建一个bmp图片System.Drawing.Image newImage = new System.Drawing.Bitmap((int)newWidth, (int)newHeight);//新建一个画板System.Drawing.Graphics newG = System.Drawing.Graphics.FromImage(newImage);//设置质量newG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;newG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;//置背景色newG.Clear(Color.White);//画图newG.DrawImage(initImage, new System.Drawing.Rectangle(0, 0, newImage.Width, newImage.Height), new System.Drawing.Rectangle(0, 0, initImage.Width, initImage.Height), System.Drawing.GraphicsUnit.Pixel);//文字水印if (watermarkText != ""){using (System.Drawing.Graphics gWater = System.Drawing.Graphics.FromImage(newImage)){System.Drawing.Font fontWater = new Font("宋体", 10);System.Drawing.Brush brushWater = new SolidBrush(Color.White);gWater.DrawString(watermarkText, fontWater, brushWater, 10, 10);gWater.Dispose();}}//透明图片水印if (watermarkImage != ""){if (File.Exists(watermarkImage)){//获取水印图片using (System.Drawing.Image wrImage = System.Drawing.Image.FromFile(watermarkImage)){//水印绘制条件：原始图片宽高均大于或等于水印图片if (newImage.Width >= wrImage.Width && newImage.Height >= wrImage.Height){Graphics gWater = Graphics.FromImage(newImage);//透明属性ImageAttributes imgAttributes = new ImageAttributes();ColorMap colorMap = new ColorMap();colorMap.OldColor = Color.FromArgb(255, 0, 255, 0);colorMap.NewColor = Color.FromArgb(0, 0, 0, 0);ColorMap[] remapTable = { colorMap };imgAttributes.SetRemapTable(remapTable, ColorAdjustType.Bitmap);float[][] colorMatrixElements = {new float[] {1.0f,  0.0f,  0.0f,  0.0f, 0.0f},new float[] {0.0f,  1.0f,  0.0f,  0.0f, 0.0f},new float[] {0.0f,  0.0f,  1.0f,  0.0f, 0.0f},new float[] {0.0f,  0.0f,  0.0f,  0.5f, 0.0f},//透明度:0.5new float[] {0.0f,  0.0f,  0.0f,  0.0f, 1.0f}};ColorMatrix wmColorMatrix = new ColorMatrix(colorMatrixElements);imgAttributes.SetColorMatrix(wmColorMatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);gWater.DrawImage(wrImage, new Rectangle(newImage.Width - wrImage.Width, newImage.Height - wrImage.Height, wrImage.Width, wrImage.Height), 0, 0, wrImage.Width, wrImage.Height, GraphicsUnit.Pixel, imgAttributes);gWater.Dispose();}wrImage.Dispose();}}}//保存缩略图newImage.Save(savePath, System.Drawing.Imaging.ImageFormat.Jpeg);//释放资源newG.Dispose();newImage.Dispose();initImage.Dispose();}}#endregion#region 其它/// 
/// 判断文件类型是否为WEB格式图片/// (注：JPG,GIF,BMP,PNG)/// 
/// HttpPostedFile.ContentType/// public static bool IsWebImage(string contentType){if (contentType == "image/pjpeg" || contentType == "image/jpeg" || contentType == "image/gif" || contentType == "image/bmp" || contentType == "image/png"){return true;}else{return false;}}#endregion}//end class}