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2011-03-04 14:11
pcajax
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C#图片处理基本应用(裁剪,缩放,清晰度,水印)
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 x 90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,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)
![](https://images.cnblogs.com/cnblogs_com/wu-jian/284049/o_2.jpg) (原图146*256) ![](https://images.cnblogs.com/cnblogs_com/wu-jian/284049/o_2_1.jpg) (裁剪要求100*100)
(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
![](https://images.cnblogs.com/cnblogs_com/wu-jian/284049/o_a.jpg) ![](https://images.cnblogs.com/cnblogs_com/wu-jian/284049/o_b.jpg)
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.Collections.Generic; |
using System.Drawing.Drawing2D; |
using System.Drawing.Imaging; |
/// 以图片中心为轴心,截取正方型,然后等比缩放 |
/// <remarks>吴剑 2010-11-23</remarks> |
/// <param name="postedFile">原图HttpPostedFile对象</param> |
/// <param name="fileSaveUrl">缩略图存放地址</param> |
/// <param name="side">指定的边长(正方型)</param> |
/// <param name="quality">质量(范围0-100)</param> |
public static void CutForSquare(System.Web.HttpPostedFile postedFile, string fileSaveUrl, int side, int quality) |
string dir = Path.GetDirectoryName(fileSaveUrl); |
if (!Directory.Exists(dir)) |
Directory.CreateDirectory(dir); |
System.Drawing.Image initImage = System.Drawing.Image.FromStream(postedFile.InputStream, true ); |
if (initImage.Width <= side && initImage.Height <= side) |
initImage.Save(fileSaveUrl, System.Drawing.Imaging.ImageFormat.Jpeg); |
int initWidth = initImage.Width; |
int initHeight = initImage.Height; |
if (initWidth != initHeight) |
System.Drawing.Image pickedImage = null ; |
System.Drawing.Graphics pickedG = null ; |
if (initWidth > initHeight) |
pickedImage = new System.Drawing.Bitmap(initHeight, initHeight); |
pickedG = System.Drawing.Graphics.FromImage(pickedImage); |
pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic; |
pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; |
Rectangle fromR = new Rectangle((initWidth - initHeight) / 2, 0, initHeight, initHeight); |
Rectangle toR = new Rectangle(0, 0, initHeight, initHeight); |
pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel); |
pickedImage = new System.Drawing.Bitmap(initWidth, initWidth); |
pickedG = System.Drawing.Graphics.FromImage(pickedImage); |
pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic; |
pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; |
Rectangle fromR = new Rectangle(0, (initHeight - initWidth) / 2, initWidth, initWidth); |
Rectangle toR = new Rectangle(0, 0, initWidth, initWidth); |
pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel); |
initImage = (System.Drawing.Image)pickedImage.Clone(); |
System.Drawing.Image resultImage = new System.Drawing.Bitmap(side, side); |
System.Drawing.Graphics resultG = System.Drawing.Graphics.FromImage(resultImage); |
resultG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic; |
resultG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; |
resultG.Clear(Color.White); |
resultG.DrawImage(initImage, new System.Drawing.Rectangle(0, 0, side, side), new System.Drawing.Rectangle(0, 0, initWidth, initHeight), System.Drawing.GraphicsUnit.Pixel); |
ImageCodecInfo[] 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" ) |
EncoderParameters ep = new EncoderParameters(1); |
ep.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, ( long )quality); |
resultImage.Save(fileSaveUrl, ici, ep); |
/// 以图片中心为轴心,截取正方型,然后等比缩放 |
/// <remarks>吴剑 2010-11-23</remarks> |
/// <param name="postedFile">原图HttpPostedFile对象</param> |
/// <param name="fileSaveUrl">缩略图存放地址</param> |
/// <param name="side">指定的边长(正方型)</param> |
/// <param name="quality">质量(范围0-100)</param> |
public static void CutForSquare(System.IO.Stream fromFile, string fileSaveUrl, int side, int quality) |
string dir = Path.GetDirectoryName(fileSaveUrl); |
if (!Directory.Exists(dir)) |
Directory.CreateDirectory(dir); |
System.Drawing.Image initImage = System.Drawing.Image.FromStream(fromFile, true ); |
if (initImage.Width <= side && initImage.Height <= side) |
initImage.Save(fileSaveUrl, System.Drawing.Imaging.ImageFormat.Jpeg); |
int initWidth = initImage.Width; |
int initHeight = initImage.Height; |
if (initWidth != initHeight) |
System.Drawing.Image pickedImage = null ; |
System.Drawing.Graphics pickedG = null ; |
if (initWidth > initHeight) |
pickedImage = new System.Drawing.Bitmap(initHeight, initHeight); |
pickedG = System.Drawing.Graphics.FromImage(pickedImage); |
pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic; |
pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; |
Rectangle fromR = new Rectangle((initWidth - initHeight) / 2, 0, initHeight, initHeight); |
Rectangle toR = new Rectangle(0, 0, initHeight, initHeight); |
pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel); |
pickedImage = new System.Drawing.Bitmap(initWidth, initWidth); |
pickedG = System.Drawing.Graphics.FromImage(pickedImage); |
pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic; |
pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; |
Rectangle fromR = new Rectangle(0, (initHeight - initWidth) / 2, initWidth, initWidth); |
Rectangle toR = new Rectangle(0, 0, initWidth, initWidth); |
pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel); |
initImage = (System.Drawing.Image)pickedImage.Clone(); |
System.Drawing.Image resultImage = new System.Drawing.Bitmap(side, side); |
System.Drawing.Graphics resultG = System.Drawing.Graphics.FromImage(resultImage); |
resultG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic; |
resultG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; |
resultG.Clear(Color.White); |
resultG.DrawImage(initImage, new System.Drawing.Rectangle(0, 0, side, side), new System.Drawing.Rectangle(0, 0, initWidth, initHeight), System.Drawing.GraphicsUnit.Pixel); |
ImageCodecInfo[] 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" ) |
EncoderParameters ep = new EncoderParameters(1); |
ep.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, ( long )quality); |
resultImage.Save(fileSaveUrl, ici, ep); |
/// 按模版比例最大范围的裁剪图片并缩放至模版尺寸 |
/// <remarks>吴剑 2010-11-15</remarks> |
/// <param name="postedFile">原图HttpPostedFile对象</param> |
/// <param name="fileSaveUrl">保存路径</param> |
/// <param name="maxWidth">最大宽(单位:px)</param> |
/// <param name="maxHeight">最大高(单位:px)</param> |
/// <param name="quality">质量(范围0-100)</param> |
public static void CutForCustom(System.Web.HttpPostedFile postedFile, string fileSaveUrl, int maxWidth, int maxHeight, int quality) |
System.Drawing.Image initImage = System.Drawing.Image.FromStream(postedFile.InputStream, true ); |
if (initImage.Width <= maxWidth && initImage.Height <= maxHeight) |
initImage.Save(fileSaveUrl, System.Drawing.Imaging.ImageFormat.Jpeg); |
double templateRate = ( double )maxWidth / maxHeight; |
double initRate = ( double )initImage.Width / initImage.Height; |
if (templateRate == initRate) |
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); |
System.Drawing.Image pickedImage = null ; |
System.Drawing.Graphics pickedG = null ; |
Rectangle fromR = new Rectangle(0, 0, 0, 0); |
Rectangle toR = new Rectangle(0, 0, 0, 0); |
if (templateRate > initRate) |
pickedImage = new System.Drawing.Bitmap(initImage.Width, ( int )Math.Floor(initImage.Width / templateRate)); |
pickedG = System.Drawing.Graphics.FromImage(pickedImage); |
fromR.Y = ( int )Math.Floor((initImage.Height - initImage.Width / templateRate) / 2); |
fromR.Width = initImage.Width; |
fromR.Height = ( int )Math.Floor(initImage.Width / templateRate); |
toR.Width = initImage.Width; |
toR.Height = ( int )Math.Floor(initImage.Width / templateRate); |
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.Width = ( int )Math.Floor(initImage.Height * templateRate); |
fromR.Height = initImage.Height; |
toR.Width = ( int )Math.Floor(initImage.Height * templateRate); |
toR.Height = initImage.Height; |
pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic; |
pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; |
pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel); |
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); |
ImageCodecInfo[] 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" ) |
EncoderParameters ep = new EncoderParameters(1); |
ep.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, ( long )quality); |
templateImage.Save(fileSaveUrl, ici, ep); |
/// <remarks>吴剑 2011-01-21</remarks> |
/// <param name="postedFile">原图HttpPostedFile对象</param> |
/// <param name="savePath">缩略图存放地址</param> |
/// <param name="targetWidth">指定的最大宽度</param> |
/// <param name="targetHeight">指定的最大高度</param> |
/// <param name="watermarkText">水印文字(为""表示不使用水印)</param> |
/// <param name="watermarkImage">水印图片路径(为""表示不使用水印)</param> |
public static void ZoomAuto(System.Web.HttpPostedFile postedFile, string savePath, System.Double targetWidth, System.Double targetHeight, string watermarkText, string watermarkImage) |
string dir = Path.GetDirectoryName(savePath); |
if (!Directory.Exists(dir)) |
Directory.CreateDirectory(dir); |
System.Drawing.Image initImage = System.Drawing.Image.FromStream(postedFile.InputStream, true ); |
if (initImage.Width <= targetWidth && initImage.Height <= targetHeight) |
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); |
if (watermarkImage != "" ) |
if (File.Exists(watermarkImage)) |
using (System.Drawing.Image wrImage = System.Drawing.Image.FromFile(watermarkImage)) |
if (initImage.Width >= wrImage.Width && initImage.Height >= wrImage.Height) |
Graphics gWater = Graphics.FromImage(initImage); |
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}, |
new 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); |
initImage.Save(savePath, System.Drawing.Imaging.ImageFormat.Jpeg); |
double newWidth = initImage.Width; |
double newHeight = initImage.Height; |
if (initImage.Width > initImage.Height || initImage.Width == initImage.Height) |
if (initImage.Width > targetWidth) |
newHeight = initImage.Height * (targetWidth / initImage.Width); |
if (initImage.Height > targetHeight) |
newHeight = targetHeight; |
newWidth = initImage.Width * (targetHeight / initImage.Height); |
System.Drawing.Image newImage = new System.Drawing.Bitmap(( int )newWidth, ( int )newHeight); |
System.Drawing.Graphics newG = System.Drawing.Graphics.FromImage(newImage); |
newG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic; |
newG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; |
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); |
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); |
if (watermarkImage != "" ) |
if (File.Exists(watermarkImage)) |
using (System.Drawing.Image wrImage = System.Drawing.Image.FromFile(watermarkImage)) |
if (newImage.Width >= wrImage.Width && newImage.Height >= wrImage.Height) |
Graphics gWater = Graphics.FromImage(newImage); |
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}, |
new 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); |
newImage.Save(savePath, System.Drawing.Imaging.ImageFormat.Jpeg); |
/// <param name="contentType">HttpPostedFile.ContentType</param> |
public static bool IsWebImage( string contentType) |
if (contentType == "image/pjpeg" || contentType == "image/jpeg" || contentType == "image/gif" || contentType == "image/bmp" || contentType == "image/png" ) |
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