C#圖片處理，縮略圖製做

準備參數：圖片文件流、文件名

 

方法：1.先將圖片流經過System.Drawing.Image.FromStream方法轉成圖片對象

　　　2.經過圖片對象.GetThumbnailImage方法生成自定義長寬的縮略圖。

生成方法：

縮略圖生成：

/// <summary>
    /// 縮略圖
    /// shidd
    /// </summary>
    /// <param name="myStream">文件流</param>
    /// <param name="serverUrl">文件名</param>
    /// <returns>字節數組</returns>
    private byte[] toImage(Stream myStream, string serverUrl)
    {
        //生成縮略圖
        //建立改變後的Stream
        var stream = new System.IO.MemoryStream();
        //取得後綴名
        string suffix = serverUrl.Substring(serverUrl.LastIndexOf("."));
        //建立一個圖像對象取得上傳圖片對象
        System.Drawing.Image myImage = System.Drawing.Image.FromStream(myStream, false);
        //int percentage= myImage.Height / myImage.Width;//原圖片比例
        //由上傳圖片產生一個縮略圖(600*400)
        System.Drawing.Image thumbImage = myImage.GetThumbnailImage(600, 400, null, System.IntPtr.Zero);
        //保存縮略圖到Stream流
        thumbImage.Save(stream, this.getImageFormat(suffix));
        //關閉縮略圖對象
        thumbImage.Dispose();
        return stream.ToArray();
    }

View Code

圖片格式：

 /// <summary>
    /// 圖片格式
    /// </summary>
    /// <param name="suffix">文件後綴</param>
    /// <returns></returns>
    private System.Drawing.Imaging.ImageFormat getImageFormat(string suffix)
    {
        System.Drawing.Imaging.ImageFormat myFormat;
        switch (suffix.ToLower())
        {
            case ".bmp":
                myFormat = System.Drawing.Imaging.ImageFormat.Bmp;
                break;
            case ".emf":
                myFormat = System.Drawing.Imaging.ImageFormat.Emf;
                break;
            case ".exif":
                myFormat = System.Drawing.Imaging.ImageFormat.Exif;
                break;
            case ".gif":
                myFormat = System.Drawing.Imaging.ImageFormat.Gif;
                break;
            case ".icon":
                myFormat = System.Drawing.Imaging.ImageFormat.Icon;
                break;
            case ".jpeg":
            case ".jpg":
                myFormat = System.Drawing.Imaging.ImageFormat.Jpeg;
                break;
            case ".png":
                myFormat = System.Drawing.Imaging.ImageFormat.Png;
                break;
            case ".tiff":
                myFormat = System.Drawing.Imaging.ImageFormat.Tiff;
                break;
            case ".wmf":
                myFormat = System.Drawing.Imaging.ImageFormat.Wmf;
                break;
            default:
                myFormat = System.Drawing.Imaging.ImageFormat.MemoryBmp;
                break;
        }
        return (myFormat);
    }

View Code

調用：

 //調用縮略圖方法
                        bytes = toImage(ms, ServerUrl);

View Code

GIF圖縮略（注：縮略後圖片不能動了，求高手指點）

 // <summary>  
    /// 爲GIF圖片生成縮略圖    
    /// </summary>  
    /// <param name="phyPath">原圖片的路徑</param>  
    /// <param name="width">縮略圖寬</param>  
    /// <param name="height">縮略圖高</param>  
    /// <returns></returns>  
    public byte[] GetThumbnail(Stream myStream, int width, int height)
    {
        //建立改變後的Stream
        var stream = new System.IO.MemoryStream();
        //建立一個圖像對象取得上傳圖片對象
        System.Drawing.Image myImage = System.Drawing.Image.FromStream(myStream, false);
        System.Drawing.Bitmap bmp = new System.Drawing.Bitmap(width, height);
        //從Bitmap建立一個System.Drawing.Graphics  
        System.Drawing.Graphics gr = System.Drawing.Graphics.FromImage(bmp);
        //設置   
        gr.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
        //下面這個也設成高質量  
        gr.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
        //下面這個設成High  
        gr.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
        //把原始圖像繪製成上面所設置寬高的縮小圖  
        System.Drawing.Rectangle rectDestination = new System.Drawing.Rectangle(0, 0, width, height);

        gr.DrawImage(myImage, rectDestination, 0, 0, myImage.Width, myImage.Height, System.Drawing.GraphicsUnit.Pixel);
        myImage.Save(stream, System.Drawing.Imaging.ImageFormat.Jpeg);
        return stream.ToArray();
    }

View Code