重提:上传图片生成略缩图“最佳解决”

从用 .Net Web 开发到现在所看到的略缩生成代码都不尽人意,要不太局限,要不失真厉害。

为此写了一个相对完善的函数供大家学习。

其中的 SaveIamge 函数提供了失真解决方法,对于处理过的图片(如加水印……)要求保持高品质可以直接调用。

using System;
using System.IO;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.Drawing.Text;
using System.Text.RegularExpressions;

/// <summary>
// 图片处理。
// http://www.hulaka.com/
// (c) 2008 Dao
/// </summary>
public class Image
{
    
/// <summary>
    
/// 缩略模式。
    
/// </summary>
    public enum ThumbMode : byte
    {
        
/// <summary>
        
/// 完整模式
        
/// </summary>
        Full = 1,
        
/// <summary>
        
/// 最大尺寸
        
/// </summary>
        Max
    }

    
/// <summary>
    
/// 缩略图。
    
/// </summary>
    
/// <param name="image">要缩略的图片</param>
    
/// <param name="size">要缩放的尺寸</param>
    
/// <param name="mode">缩略模式</param>
    
/// <param name="contentAlignment">对齐方式</param>
    
/// <returns>返回已经缩放的图片。</returns>
    public static Bitmap Thumbnail(Bitmap image, Size size, ThumbMode mode, ContentAlignment contentAlignment)
    {
        
if (!size.IsEmpty && !image.Size.IsEmpty && !size.Equals(image.Size))
        {
            
//先取一个宽比例。
            double scale = (double)image.Width / (double)size.Width;
            
//缩略模式
            switch (mode)
            {
                
case ThumbMode.Full:
                    
if (image.Height > image.Width)
                        scale 
= (double)image.Height / (double)size.Height;
                    
break;
                
case ThumbMode.Max:
                    
if (image.Height / scale < size.Height)
                        scale 
= (double)image.Height / (double)size.Height;
                    
break;
            }
            SizeF newSzie 
= new SizeF((float)(image.Width / scale), (float)(image.Height / scale));
            Bitmap result 
= new Bitmap(size.Width, size.Height);
            
using (Graphics g = Graphics.FromImage(result))
            {
                g.FillRectangle(Brushes.White, 
new Rectangle(new Point(00), size));
                g.InterpolationMode 
= InterpolationMode.HighQualityBicubic;
                g.SmoothingMode 
= SmoothingMode.HighQuality;
                g.PixelOffsetMode 
= PixelOffsetMode.HighQuality;
                g.CompositingMode 
= CompositingMode.SourceOver;
                g.CompositingQuality 
= CompositingQuality.HighQuality;
                g.TextRenderingHint 
= TextRenderingHint.AntiAliasGridFit;
                
//对齐方式
                RectangleF destRect;
                
switch (contentAlignment)
                {
                    
case ContentAlignment.TopCenter:
                        destRect 
= new RectangleF(new PointF(-(float)((newSzie.Width - size.Width) * 0.5), 0), newSzie);
                        
break;
                    
case ContentAlignment.TopRight:
                        destRect 
= new RectangleF(new PointF(-(float)(newSzie.Width - size.Width), 0), newSzie);
                        
break;
                    
case ContentAlignment.MiddleLeft:
                        destRect 
= new RectangleF(new PointF(0-(float)((newSzie.Height - size.Height) * 0.5)), newSzie);
                        
break;
                    
case ContentAlignment.MiddleCenter:
                        destRect 
= new RectangleF(new PointF(-(float)((newSzie.Width - size.Width) * 0.5), -(float)((newSzie.Height - size.Height) * 0.5)), newSzie);
                        
break;
                    
case ContentAlignment.MiddleRight:
                        destRect 
= new RectangleF(new PointF(-(float)(newSzie.Width - size.Width), -(float)((newSzie.Height - size.Height) * 0.5)), newSzie);
                        
break;
                    
case ContentAlignment.BottomLeft:
                        destRect 
= new RectangleF(new PointF(0-(float)(newSzie.Height - size.Height)), newSzie);
                        
break;
                    
case ContentAlignment.BottomCenter:
                        destRect 
= new RectangleF(new PointF(-(float)((newSzie.Width - size.Width) * 0.5), -(float)(newSzie.Height - size.Height)), newSzie);
                        
break;
                    
case ContentAlignment.BottomRight:
                        destRect 
= new RectangleF(new PointF(-(float)(newSzie.Width - size.Width), -(float)(newSzie.Height - size.Height)), newSzie);
                        
break;
                    
default:
                        destRect 
= new RectangleF(new PointF(00), newSzie);
                        
break;
                }
                g.DrawImage(image, destRect, 
new RectangleF(new PointF(0F, 0F), image.Size), GraphicsUnit.Pixel);
                image.Dispose();
            }
            
return result;
        }
        
else
            
return image;
    }

    
/// <summary>
    
/// 保存图片。
    
/// </summary>
    
/// <param name="image">要保存的图片</param>
    
/// <param name="quality">品质(1L~100L之间,数值越大品质越好)</param>
    
/// <param name="filename">保存路径</param>
    public static void SaveIamge(Bitmap image, long quality, string filename)
    {
        
using (EncoderParameters encoderParams = new EncoderParameters(1))
        {
            
using (EncoderParameter parameter = (encoderParams.Param[0= new EncoderParameter(Encoder.Quality, quality)))
            {
                ImageCodecInfo encoder 
= null;
                
//取得扩展名
                string ext = Path.GetExtension(filename);
                
if (string.IsNullOrEmpty(ext))
                    ext 
= ".jpg";
                
//根据扩展名得到解码、编码器
                foreach (ImageCodecInfo codecInfo in ImageCodecInfo.GetImageEncoders())
                {
                    
if (Regex.IsMatch(codecInfo.FilenameExtension, string.Format(@"(;|^)\*\{0}(;|$)", ext), RegexOptions.IgnoreCase))
                    {
                        encoder 
= codecInfo;
                        
break;
                    }
                }
                Directory.CreateDirectory(Path.GetDirectoryName(filename));
                image.Save(filename, encoder, encoderParams);
            }
        }
    }

    
/// <summary>
    
/// 保存图片。
    
/// </summary>
    
/// <param name="stream">要保存的流</param>
    
/// <param name="quality">品质(1L~100L之间,数值越大品质越好)</param>
    
/// <param name="filename">保存路径</param>
    public static void SaveIamge(Stream stream, long quality, string filename)
    {
        
using (Bitmap bmpTemp = new Bitmap(stream))
        {
            SaveIamge(bmpTemp, quality, filename);
        }
    }
}

调用方法如下:
using (Bitmap bmpAvatar = Image.Thumbnail(new Bitmap(/*<流,FileUpload 控件的 PostedFile.InputStream 属性>*/), new Size(4848), Image.ThumbMode.Full, ContentAlignment.MiddleCenter))
{
    Image.SaveIamge(bmpAvatar, 
95L, Server.MapPath("~/upfiles/Avatar.jpg"));
}


演示程序:



下载演示程序

posted @ 2008-02-24 17:36  raydao  阅读(4879)  评论(13编辑  收藏  举报