2013年9月17日 星期二

[轉貼] C#圖片處理高級應用(裁剪,縮放,清晰度,浮水印)


前言
需求源自項目中的一些應用,比如相冊功能,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。隨便看一下,大部分網站基本都是將原圖等比縮放來生成縮略圖。但完美主義者會發現一些問題,比如顯示排版時想讓相片縮略圖列表非常統一、整齊、和美觀,比如要求每張縮略圖大小固定為120 x 90且不拉伸變形怎麼辦?再比如用戶頭像如何讓縮略圖比原圖更清晰?或是如何在上傳的圖片下加一個半透明的LOGO水印?
OK,本文根據自己的項目代碼描述以上問題的解決方案,所謂C#圖片處理高級應用,感覺有點標題黨了,這些功能並無多大技術含量。全部基於.Net Framework類庫完成,代碼中包含了C#圖片處理的一些基礎知識,與大家分享,個人能力有限,不足之處還請及時指正。
提高縮略圖清晰度
(原圖200*200,12.3k)(處理後80*80,17.7k)
之前一直認為縮略圖不可能比原圖清晰,直到某天一位產品的同事給我看某網站的效果。於是開始尋找.NET下實現代碼,仔細觀察縮略圖確實比原圖更清晰了一些,但代價是縮略圖文件比原圖更大,所以如果你想讓一張佔滿顯示器屏幕的超大圖片更清晰,那麼圖片佔用空間和網絡流量就必需考慮了,如果是互聯網應用,建議縮略圖在200像素以內的使用該方法。當然如果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清晰還請分享。
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,最大範圍的對原圖進行裁剪,然後對裁剪結果等比縮放。
圖片水印
僅演示了效果,如需要變更字體、水印透明度、位置等可自行在代碼或方法中擴展。
代碼
封裝了幾個通用的方法,如發現有BUG或漏洞還請及時指正。
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
{
    /// <summary>
    /// 圖片處理類
    /// 吳劍 2008-07-02 創建
    /// 吳劍 2011-01-21 修改
    /// </summary>
    public class PTImage
    {
        #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
        /// 用於頭像處理
        /// </summary>
        /// <remarks>吳劍 2010-11-23</remarks>
        /// <param name="postedFile">原圖HttpPostedFile對像</param>
        /// <param name="fileSaveUrl">縮略圖存放地址</param>
        /// <param name="side">指定的邊長(正方型)</param>
        /// <param name="quality">質量(範圍0-100)</param>
        public static void CutForSquare(System.Web.HttpPostedFile postedFile, string fileSaveUrl, int side, int quality)
        {
            //創建目錄
            string dir = Path.GetDirectoryName(fileSaveUrl);
            if (!Directory.Exists(dir))
                Directory.CreateDirectory(dir);
  
            //原始圖片(獲取原始圖片創建對象,並使用流中嵌入的顏色管理信息)
            System.Drawing.Image initImage = System.Drawing.Image.FromStream(postedFile.InputStream, true);
  
            //原圖寬高均小於模版,不作處理,直接保存
            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)
                {
                    //截圖對像
                    System.Drawing.Image pickedImage = null;
                    System.Drawing.Graphics pickedG = null;
  
                    //寬大於高的橫圖
                    if (initWidth > initHeight)
                    {
                        //對像實例化
                        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;
                    }
                    //高大於寬的豎圖
                    else
                    {
                        //對像實例化
                        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;
                    }
  
                    //將截圖對像賦給原圖
                    initImage = (System.Drawing.Image)pickedImage.Clone();
                    //釋放截圖資源
                    pickedG.Dispose();
                    pickedImage.Dispose();
                }
  
                //縮略圖對像
                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;
                //用指定背景色清空畫布
                resultG.Clear(Color.White);
                //繪製縮略圖
                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
                //獲取系統編碼類型數組,包含了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);
  
                //保存縮略圖
                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();
            }
        }
  
        /// <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
        /// 用於頭像處理
        /// </summary>
        /// <remarks>吳劍 2010-11-23</remarks>
        /// <param name="postedFile">原圖HttpPostedFile對像</param>
        /// <param name="fileSaveUrl">縮略圖存放地址</param>
        /// <param name="side">指定的邊長(正方型)</param>
        /// <param name="quality">質量(範圍0-100)</param>
        public static void CutForSquare(System.IO.Stream fromFile, string fileSaveUrl, int side, int quality)
        {
            //創建目錄
            string dir = Path.GetDirectoryName(fileSaveUrl);
            if (!Directory.Exists(dir))
                Directory.CreateDirectory(dir);
  
            //原始圖片(獲取原始圖片創建對象,並使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,不作處理,直接保存
            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)
                {
                    //截圖對像
                    System.Drawing.Image pickedImage = null;
                    System.Drawing.Graphics pickedG = null;
  
                    //寬大於高的橫圖
                    if (initWidth > initHeight)
                    {
                        //對像實例化
                        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);

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