C#裁剪,縮放,明晰度,水印處置操作示例

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前言

需求源自項目中的一些使用，比方相冊功用，通常用戶上傳相片後我們都會針對該相片再生成一張縮略圖，用於其它頁面上的列表顯示。隨意看一下，大局部網站根本都是將原圖等比縮放來生成縮略圖。但完滿主義者會發現一些問題，比方顯示排版時想讓相片縮略圖列表十分一致、劃一、和美觀，比方要求每張縮略圖大小固定為120 x 90且不拉伸變形怎樣辦？再比方用戶頭像如何讓縮略圖比原圖更明晰？或是如何在上傳的圖片下加一個半通明的LOGO水印？

OK，本文依據自己的項目代碼描繪以上問題的處理方案，全部基於.Net Framework類庫完成，代碼中包括了C#圖片處置的一些根底知識，與大家分享，團體才能無限，缺乏之處還請及時指正。

進步縮略圖明晰度

(原圖200*200,12.3k)(處置後80*80,17.7k)

之前不斷以為縮略圖不能夠比原圖明晰，直到某天一位產品的同事給我看某網站的效果。於是開端尋覓.NET下完成代碼，細心察看縮略圖的確比原圖更明晰了一些，但代價是縮略圖文件比原圖更大，所以假如你想讓一張占滿顯示器屏幕的超大圖片更明晰，那麼圖片占用空間和網絡流量就必需思索了，假如是互聯網使用，建議縮略圖在200像素以內的運用該辦法。當然假如哪位有更好的代碼即能讓圖片文件大小變化不大又讓圖片更明晰還請分享。

圖片裁剪

(原圖256*192)(裁剪要求100*100)

(原圖256*192)(裁剪要求90*120)

(原圖256*192)(裁剪要求120*90)

(原圖146*256)(裁剪要求100*100)

(原圖146*256)(裁剪要求90*120)

(原圖146*256)(裁剪要求120*90)

算法：以原圖中心作為裁剪中心，最大范圍的對原圖停止裁剪，然後對裁剪後果等比縮放。

圖片水印

僅演示了效果，如需求變卦字體、水印通明度、地位等可自行在代碼或辦法中擴展。

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
{
 /// <summary>
 /// 圖片處置
 /// http://www.cnblogs.com/wu-jian/
 /// 
 /// 吳劍 2011-02-20 創立
 /// 吳劍 2012-08-08 修正
 /// </summary>
 public class Image
 {
  #region 正方型裁剪並縮放

  /// <summary>
  /// 正方型裁剪
  /// 以圖片中心為軸心，截取正方型，然後等比縮放
  /// 用於頭像處置
  /// </summary>
  /// <remarks>吳劍 2012-08-08</remarks>
  /// <param name="fromFile">原圖Stream對象</param>
  /// <param name="fileSaveUrl">縮略圖寄存地址</param>
  /// <param name="side">指定的邊長（正方型）</param>
  /// <param name="quality">質量（范圍0-100）</param>
  public static void CutForSquare(System.IO.Stream fromFile, string fileSaveUrl, int side, int quality)
  {
   //創立目錄
   string dir = Path.GetDirectoryName(fileSaveUrl);
   if (!Directory.Exists(dir))
    Directory.CreateDirectory(dir);

   //原始圖片（獲取原始圖片創立對象，並運用流中嵌入的顏色管理信息）
   System.Drawing.Image initImage = System.Drawing.Image.FromStream(fromFile, true);

   //原圖寬高均小於模版，不作處置，直接保管
   if (initImage.Width <= side && initImage.Height <= side)
   {
    initImage.Save(fileSaveUrl, System.Drawing.Imaging.ImageFormat.Jpeg);
   }
   else
   {
    //原始圖片的寬、高
    int initWidth = initImage.Width;
    int initHeight = initImage.Height;

    //非正方型先裁剪為正方型
    if (initWidth != initHeight)
    {
     //截圖對象
     System.Drawing.Image pickedImage = null;
     System.Drawing.Graphics pickedG = null;

     //嚴懲於高的橫圖
     if (initWidth > initHeight)
     {
      //對象實例化
      pickedImage = new System.Drawing.Bitmap(initHeight, initHeight);
      pickedG = System.Drawing.Graphics.FromImage(pickedImage);
      //設置質量
      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);
      //畫圖
      pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel);
      //重置寬
      initWidth = initHeight;
     }
     //矮小於寬的豎圖
     else
     {
      //對象實例化
      pickedImage = new System.Drawing.Bitmap(initWidth, initWidth);
      pickedG = System.Drawing.Graphics.FromImage(pickedImage);
      //設置質量
      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);
      //畫圖
      pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel);
      //重置高
      initHeight = initWidth;
     }

     //將截圖對象賦給原圖
     initImage = (System.Drawing.Image)pickedImage.Clone();
     //釋放截圖資源
     pickedG.Dispose();
     pickedImage.Dispose();
    }

    //縮略圖對象
    System.Drawing.Image resultImage = new System.Drawing.Bitmap(side, side);
    System.Drawing.Graphics resultG = System.Drawing.Graphics.FromImage(resultImage);
    //設置質量
    resultG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
    resultG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
    //用指定背風光清空畫布
    resultG.Clear(Color.White);
    //繪制縮略圖
    resultG.DrawImage(initImage, new System.Drawing.Rectangle(0, 0, side, side), new System.Drawing.Rectangle(0, 0, initWidth, initHeight), System.Drawing.GraphicsUnit.Pixel);

    //關鍵質量控制
    //獲取零碎編碼類型數組,包括了jpeg,bmp,png,gif,tiff
    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")
     {
      ici = i;
     }
    }
    EncoderParameters ep = new EncoderParameters(1);
    ep.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, (long)quality);

    //保管縮略圖
    resultImage.Save(fileSaveUrl, ici, ep);

    //釋放關鍵質量控制所用資源
    ep.Dispose();

    //釋放縮略圖資源
    resultG.Dispose();
    resultImage.Dispose();

    //釋放原始圖片資源
    initImage.Dispose();
   }
  }

  #endregion

  #region 自定義裁剪並縮放

  /// <summary>
  /// 指定長寬裁剪
  /// 按模版比例最大范圍的裁剪圖片並縮放至模版尺寸
  /// </summary>
  /// <remarks>吳劍 2012-08-08</remarks>
  /// <param name="fromFile">原圖Stream對象</param>
  /// <param name="fileSaveUrl">保管途徑</param>
  /// <param name="maxWidth">最大寬(單位:px)</param>
  /// <param name="maxHeight">最大高(單位:px)</param>
  /// <param name="quality">質量（范圍0-100）</param>
  public static void CutForCustom(System.IO.Stream fromFile, string fileSaveUrl, int maxWidth, int maxHeight, int quality)
  {
   //從文件獲取原始圖片，並運用流中嵌入的顏色管理信息
   System.Drawing.Image initImage = System.Drawing.Image.FromStream(fromFile, true);

   //原圖寬高均小於模版，不作處置，直接保管
   if (initImage.Width <= maxWidth && initImage.Height <= maxHeight)
   {
    initImage.Save(fileSaveUrl, System.Drawing.Imaging.ImageFormat.Jpeg);
   }
   else
   {
    //模版的寬高比例
    double templateRate = (double)maxWidth / maxHeight;
    //原圖片的寬高比例
    double initRate = (double)initImage.Width / initImage.Height;

    //原圖與模版比例相等，直接縮放
    if (templateRate == initRate)
    {
     //按模版大小生成最終圖片
     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);
    }
    //原圖與模版比例不等，裁剪後縮放
    else
    {
     //裁剪對象
     System.Drawing.Image pickedImage = null;
     System.Drawing.Graphics pickedG = null;

     //定位
     Rectangle fromR = new Rectangle(0, 0, 0, 0);//原圖裁剪定位
     Rectangle toR = new Rectangle(0, 0, 0, 0);//目的定位

     //寬為規范停止裁剪
     if (templateRate > initRate)
     {
      //裁剪對象實例化
      pickedImage = new System.Drawing.Bitmap(initImage.Width, (int)System.Math.Floor(initImage.Width / templateRate));
      pickedG = System.Drawing.Graphics.FromImage(pickedImage);

      //裁剪源定位
      fromR.X = 0;
      fromR.Y = (int)System.Math.Floor((initImage.Height - initImage.Width / templateRate) / 2);
      fromR.Width = initImage.Width;
      fromR.Height = (int)System.Math.Floor(initImage.Width / templateRate);

      //裁剪目的定位
      toR.X = 0;
      toR.Y = 0;
      toR.Width = initImage.Width;
      toR.Height = (int)System.Math.Floor(initImage.Width / templateRate);
     }
     //高為規范停止裁剪
     else
     {
      pickedImage = new System.Drawing.Bitmap((int)System.Math.Floor(initImage.Height * templateRate), initImage.Height);
      pickedG = System.Drawing.Graphics.FromImage(pickedImage);

      fromR.X = (int)System.Math.Floor((initImage.Width - initImage.Height * templateRate) / 2);
      fromR.Y = 0;
      fromR.Width = (int)System.Math.Floor(initImage.Height * templateRate);
      fromR.Height = initImage.Height;

      toR.X = 0;
      toR.Y = 0;
      toR.Width = (int)System.Math.Floor(initImage.Height * templateRate);
      toR.Height = initImage.Height;
     }

     //設置質量
     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);

     //按模版大小生成最終圖片
     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);

     //關鍵質量控制
     //獲取零碎編碼類型數組,包括了jpeg,bmp,png,gif,tiff
     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")
      {
       ici = i;
      }
     }
     EncoderParameters ep = new EncoderParameters(1);
     ep.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, (long)quality);

     //保管縮略圖
     templateImage.Save(fileSaveUrl, ici, ep);
     //templateImage.Save(fileSaveUrl, System.Drawing.Imaging.ImageFormat.Jpeg);

     //釋放資源
     templateG.Dispose();
     templateImage.Dispose();

     pickedG.Dispose();
     pickedImage.Dispose();
    }
   }

   //釋放資源
   initImage.Dispose();
  }
  #endregion

  #region 等比縮放

  /// <summary>
  /// 圖片等比縮放
  /// </summary>
  /// <remarks>吳劍 2012-08-08</remarks>
  /// <param name="fromFile">原圖Stream對象</param>
  /// <param name="savePath">縮略圖寄存地址</param>
  /// <param name="targetWidth">指定的最大寬度</param>
  /// <param name="targetHeight">指定的最大高度</param>
  /// <param name="watermarkText">水印文字(為""表示不運用水印)</param>
  /// <param name="watermarkImage">水印圖片途徑(為""表示不運用水印)</param>
  public static void ZoomAuto(System.IO.Stream fromFile, string savePath, System.Double targetWidth, System.Double targetHeight, string watermarkText, string watermarkImage)
  {
   //創立目錄
   string dir = Path.GetDirectoryName(savePath);
   if (!Directory.Exists(dir))
    Directory.CreateDirectory(dir);

   //原始圖片（獲取原始圖片創立對象，並運用流中嵌入的顏色管理信息）
   System.Drawing.Image initImage = System.Drawing.Image.FromStream(fromFile, true);

   //原圖寬高均小於模版，不作處置，直接保管
   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("黑體", 10);
      System.Drawing.Brush brushWater = new SolidBrush(Color.White);
      gWater.DrawString(watermarkText, fontWater, brushWater, 10, 10);
      gWater.Dispose();
     }
    }

    //通明圖片水印
    if (watermarkImage != "")
    {
     if (File.Exists(watermarkImage))
     {
      //獲取水印圖片
      using (System.Drawing.Image wrImage = System.Drawing.Image.FromFile(watermarkImage))
      {
       //水印繪制條件：原始圖片寬高均大於或等於水印圖片
       if (initImage.Width >= wrImage.Width && initImage.Height >= wrImage.Height)
       {
        Graphics gWater = Graphics.FromImage(initImage);

        //通明屬性
        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},//通明度:0.5
         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);

        gWater.Dispose();
       }
       wrImage.Dispose();
      }
     }
    }

    //保管
    initImage.Save(savePath, System.Drawing.Imaging.ImageFormat.Jpeg);
   }
   else
   {
    //縮略圖寬、高計算
    double newWidth = initImage.Width;
    double newHeight = initImage.Height;

    //嚴懲於高或寬等於高（橫圖或正方）
    if (initImage.Width > initImage.Height || initImage.Width == initImage.Height)
    {
     //假如嚴懲於模版
     if (initImage.Width > targetWidth)
     {
      //寬按模版，高按比例縮放
      newWidth = targetWidth;
      newHeight = initImage.Height * (targetWidth / initImage.Width);
     }
    }
    //矮小於寬（豎圖）
    else
    {
     //假如矮小於模版
     if (initImage.Height > targetHeight)
     {
      //高按模版，寬按比例縮放
      newHeight = targetHeight;
      newWidth = initImage.Width * (targetHeight / initImage.Height);
     }
    }

    //生成新圖
    //新建一個bmp圖片
    System.Drawing.Image newImage = new System.Drawing.Bitmap((int)newWidth, (int)newHeight);
    //新建一個畫板
    System.Drawing.Graphics newG = System.Drawing.Graphics.FromImage(newImage);

    //設置質量
    newG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
    newG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

    //置背風光
    newG.Clear(Color.White);
    //畫圖
    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("宋體", 10);
      System.Drawing.Brush brushWater = new SolidBrush(Color.White);
      gWater.DrawString(watermarkText, fontWater, brushWater, 10, 10);
      gWater.Dispose();
     }
    }

    //通明圖片水印
    if (watermarkImage != "")
    {
     if (File.Exists(watermarkImage))
     {
      //獲取水印圖片
      using (System.Drawing.Image wrImage = System.Drawing.Image.FromFile(watermarkImage))
      {
       //水印繪制條件：原始圖片寬高均大於或等於水印圖片
       if (newImage.Width >= wrImage.Width && newImage.Height >= wrImage.Height)
       {
        Graphics gWater = Graphics.FromImage(newImage);

        //通明屬性
        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},//通明度:0.5
         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);
        gWater.Dispose();
       }
       wrImage.Dispose();
      }
     }
    }

    //保管縮略圖
    newImage.Save(savePath, System.Drawing.Imaging.ImageFormat.Jpeg);

    //釋放資源
    newG.Dispose();
    newImage.Dispose();
    initImage.Dispose();
   }
  }

  #endregion

  #region 其它

  /// <summary>
  /// 判別文件類型能否為WEB格式圖片
  /// (注：JPG,GIF,BMP,PNG)
  /// </summary>
  /// <param name="contentType">HttpPostedFile.ContentType</param>
  /// <returns></returns>
  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
}

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