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

namespace Discuz.Common
{
	/// <summary>
	/// Thumbnail 的摘要说明。
	/// </summary>
	public class Thumbnail
	{
		private Image srcImage;
		private string srcFileName;		
		
		/// <summary>
		/// 创建
		/// </summary>
		/// <param name="FileName">原始图片路径</param>
		public bool SetImage(string FileName)
		{
			srcFileName = Utils.GetMapPath(FileName);
			try
			{
				srcImage = Image.FromFile(srcFileName);
			}
			catch
			{
				return false;
			}
			return true;

		}

		/// <summary>
		/// 回调
		/// </summary>
		/// <returns></returns>
		public bool ThumbnailCallback()
		{
			return false;
		}

		/// <summary>
		/// 生成缩略图,返回缩略图的Image对象
		/// </summary>
		/// <param name="Width">缩略图宽度</param>
		/// <param name="Height">缩略图高度</param>
		/// <returns>缩略图的Image对象</returns>
		public Image GetImage(int Width,int Height)
		{
			Image img;
			Image.GetThumbnailImageAbort callb = new Image.GetThumbnailImageAbort(ThumbnailCallback); 
 			img = srcImage.GetThumbnailImage(Width,Height,callb, IntPtr.Zero);
 			return img;
		}

		/// <summary>
		/// 保存缩略图
		/// </summary>
		/// <param name="Width"></param>
		/// <param name="Height"></param>
		public void SaveThumbnailImage(int Width,int Height)
		{
			switch(Path.GetExtension(srcFileName).ToLower())
			{
				case ".png":
					SaveImage(Width, Height, ImageFormat.Png);
					break;
				case ".gif":
					SaveImage(Width, Height, ImageFormat.Gif);
					break;
				default:
					SaveImage(Width, Height, ImageFormat.Jpeg);
					break;
			}
		}

		/// <summary>
		/// 生成缩略图并保存
		/// </summary>
		/// <param name="Width">缩略图的宽度</param>
		/// <param name="Height">缩略图的高度</param>
		/// <param name="imgformat">保存的图像格式</param>
		/// <returns>缩略图的Image对象</returns>
		public void SaveImage(int Width,int Height, ImageFormat imgformat)
		{
            if (imgformat != ImageFormat.Gif && (srcImage.Width > Width) || (srcImage.Height > Height))
            {
                Image img;
                Image.GetThumbnailImageAbort callb = new Image.GetThumbnailImageAbort(ThumbnailCallback);
                img = srcImage.GetThumbnailImage(Width, Height, callb, IntPtr.Zero);
                srcImage.Dispose();
                img.Save(srcFileName, imgformat);
                img.Dispose();
            }
		}

		#region Helper

		/// <summary>
		/// 保存图片
		/// </summary>
		/// <param name="image">Image 对象</param>
		/// <param name="savePath">保存路径</param>
		/// <param name="ici">指定格式的编解码参数</param>
		private static void SaveImage(Image image, string savePath, ImageCodecInfo ici)
		{
			//设置 原图片 对象的 EncoderParameters 对象
			EncoderParameters parameters = new EncoderParameters(1);
			parameters.Param[0] = new EncoderParameter(Encoder.Quality, ((long) 100));
			image.Save(savePath, ici, parameters);
			parameters.Dispose();
		}

		/// <summary>
		/// 获取图像编码解码器的所有相关信息
		/// </summary>
		/// <param name="mimeType">包含编码解码器的多用途网际邮件扩充协议 (MIME) 类型的字符串</param>
		/// <returns>返回图像编码解码器的所有相关信息</returns>
		private static ImageCodecInfo GetCodecInfo(string mimeType)
		{
			ImageCodecInfo[] CodecInfo = ImageCodecInfo.GetImageEncoders();
			foreach(ImageCodecInfo ici in CodecInfo)
			{
				if(ici.MimeType == mimeType)
                    return ici;
			}
			return null;
		}

		/// <summary>
		/// 计算新尺寸
		/// </summary>
		/// <param name="width">原始宽度</param>
		/// <param name="height">原始高度</param>
		/// <param name="maxWidth">最大新宽度</param>
		/// <param name="maxHeight">最大新高度</param>
		/// <returns></returns>
		private static Size ResizeImage(int width, int height, int maxWidth, int maxHeight)
		{
			decimal MAX_WIDTH = (decimal)maxWidth;
			decimal MAX_HEIGHT = (decimal)maxHeight;
			decimal ASPECT_RATIO = MAX_WIDTH / MAX_HEIGHT;

			int newWidth, newHeight;
			decimal originalWidth = (decimal)width;
			decimal originalHeight = (decimal)height;
			
			if (originalWidth > MAX_WIDTH || originalHeight > MAX_HEIGHT) 
			{
				decimal factor;
				// determine the largest factor 
				if (originalWidth / originalHeight > ASPECT_RATIO) 
				{
					factor = originalWidth / MAX_WIDTH;
					newWidth = Convert.ToInt32(originalWidth / factor);
					newHeight = Convert.ToInt32(originalHeight / factor);
				} 
				else 
				{
					factor = originalHeight / MAX_HEIGHT;
					newWidth = Convert.ToInt32(originalWidth / factor);
					newHeight = Convert.ToInt32(originalHeight / factor);
				}	  
			} 
			else 
			{
				newWidth = width;
				newHeight = height;
			}
			return new Size(newWidth,newHeight);			
		}

		/// <summary>
		/// 得到图片格式
		/// </summary>
		/// <param name="name">文件名称</param>
		/// <returns></returns>
		public static ImageFormat GetFormat(string name)
		{
			string ext = name.Substring(name.LastIndexOf(".") + 1);
			switch(ext.ToLower())
			{
				case "jpg":
				case "jpeg":
					return ImageFormat.Jpeg;
				case "bmp":
					return ImageFormat.Bmp;
				case "png":
					return ImageFormat.Png;
				case "gif":
					return ImageFormat.Gif;
				default:
					return ImageFormat.Jpeg;
			}
		}
		#endregion

		/// <summary>
		/// 制作小正方形
		/// </summary>
		/// <param name="fileName">原图的文件路径</param>
		/// <param name="newFileName">新地址</param>
		/// <param name="newSize">长度或宽度</param>
		public static void MakeSquareImage(string fileName, string newFileName, int newSize)
		{
			Image image = Image.FromFile(fileName);
	
			int i = 0;
			int width = image.Width;
			int height = image.Height;
			if (width > height)
				i = height;
			else
				i = width;

            Bitmap b = new Bitmap(newSize, newSize);

			try
			{
				Graphics g = Graphics.FromImage(b);
				g.InterpolationMode = InterpolationMode.High;
				g.SmoothingMode = SmoothingMode.HighQuality;

				//清除整个绘图面并以透明背景色填充
				g.Clear(Color.Transparent);
				if (width < height)
					g.DrawImage(image,  new Rectangle(0, 0, newSize, newSize), new Rectangle(0, (height-width)/2, width, width), GraphicsUnit.Pixel);
				else
					g.DrawImage(image, new Rectangle(0, 0, newSize, newSize), new Rectangle((width-height)/2, 0, height, height), GraphicsUnit.Pixel);

                SaveImage(b, newFileName, GetCodecInfo("image/" + GetFormat(fileName).ToString().ToLower()));
			}
			finally
			{
				image.Dispose();
				b.Dispose();
			}
		}

		/// <summary>
		/// 制作缩略图
		/// </summary>
		/// <param name="fileName">原图路径</param>
		/// <param name="newFileName">新图路径</param>
		/// <param name="maxWidth">最大宽度</param>
		/// <param name="maxHeight">最大高度</param>
		public static void MakeThumbnailImage(string fileName, string newFileName, int maxWidth, int maxHeight)
		{
			Image original = Image.FromFile(fileName);
			Size _newSize = ResizeImage(original.Width,original.Height,maxWidth, maxHeight);
			Image displayImage = new Bitmap(original,_newSize);

			try
			{
				displayImage.Save(newFileName, GetFormat(fileName));   
			}
			finally
			{
				original.Dispose();
			}	
		}
	}
}
