exifpropertyformatter.cs

本系统是在asp版《在线文件管理器》的基础上设计制作

			
			if (format == FormatInstruction.ALLCHAR) 
			{
				System.Text.ASCIIEncoding encoding = new System.Text.ASCIIEncoding();
				strRet = encoding.GetString(propItem.Value, 0, propItem.Len);
			}
			else if (format == FormatInstruction.UNICODE)
			{
				System.Text.UnicodeEncoding unicode = new System.Text.UnicodeEncoding();
				strRet = unicode.GetString(propItem.Value, 0, propItem.Len);
			}
			else if (format == FormatInstruction.USERCOMMENT)
			{
				System.Text.ASCIIEncoding encoding = new System.Text.ASCIIEncoding();
				string encodingTag = encoding.GetString(propItem.Value, 0, 8).ToUpper();
				
				if (encodingTag.StartsWith("ASCII"))
				{
					strRet = encoding.GetString(propItem.Value, 8, propItem.Len-8);
				}
				else if (encodingTag.StartsWith("JIS"))
				{
					System.Text.Encoding shiftJis = System.Text.Encoding.GetEncoding(932);
					strRet = shiftJis.GetString(propItem.Value, 8, propItem.Len-8);
				}
				else if (encodingTag.StartsWith("UNICODE"))
				{
					System.Text.UnicodeEncoding unicode = new System.Text.UnicodeEncoding();
					strRet = unicode.GetString(propItem.Value, 8, propItem.Len-8);
				}
				else if (encodingTag.StartsWith("\0\0\0\0\0\0\0\0"))
				{
					strRet = "";
				}
				else
				{
					strRet = encoding.GetString(propItem.Value, 0, propItem.Len);
				}
			}
			else
			{
				strRet = BitConverter.ToString(propItem.Value, 0, propItem.Len);
			}

			return strRet;
		}

		/// <summary>
		/// Format a SLong tag (signed).
		/// </summary>
		/// <param name="propItem">The <see cref="PropertyItem"/> to format.</param>
		/// <returns>A formatted signed Long (<see cref="Int32"/> string.</returns>
		private static string FormatTagSLong(PropertyItem propItem)
		{
			string strRet = "";
			
			for (int i = 0; i < propItem.Len; i = i + BYTEJUMP_SLONG) 
			{
				System.Int32 val = BitConverter.ToInt32(propItem.Value, i);
				strRet += val.ToString();
				if (i + BYTEJUMP_SLONG < propItem.Len) strRet += " ";
			}

			return strRet;
		}

		/// <summary>
		/// Format a SRational tag (signed).
		/// </summary>
		/// <param name="propItem">The <see cref="PropertyItem"/> to format.</param>
		/// <param name="FormatInstruction">The <see cref="FormatInstruction"/> to use for formatting.</param>
		/// <returns>A formatted signed Rational string.</returns>
		/// <remarks>By defailt a string will be formatted as decimal unless the <see cref="FormatInstruction"/> is <see cref="FormatInstruction.FRACTION"/></remarks>
		private static string FormatTagSRational(PropertyItem propItem, FormatInstruction format)
		{
			string strRet = "";
			
			for (int i = 0; i < propItem.Len; i = i + BYTEJUMP_SRATIONAL) 
			{
				System.Int32 numer = BitConverter.ToInt32(propItem.Value, i);
				System.Int32 denom = BitConverter.ToInt32(propItem.Value, i + BYTEJUMP_SLONG);
				
				if (format == FormatInstruction.FRACTION) 
				{
					strRet += ToRationalString(numer, denom);
				}
				else 
				{
					double dbl;

					if (denom  == 0) dbl = 0.0;
					else dbl = (double)numer / (double)denom;
					
					strRet += dbl.ToString(DOUBLETYPE_FORMAT);
				}
				if (i + BYTEJUMP_SRATIONAL < propItem.Len) strRet += " ";
			}
			return strRet;
		}

		#region Formatting a Rational
		// //////////////////////////////////////////////////////////
		// Formatting a Rational
		// ---------------------
		// Modified from:
		//		Java Software Solutions: Foundations of Program Design e/3
		//		by John Lewis and William Loftus
		//		Published by Addison Wesley
		//		ISBN: 0-201-78129-8
		//		Copyright 2003
		
		// //////////////////////////////////////////////////////////
		// Format a signed rational
		// //////////////////////////////////////////////////////////

		/// <summary>
		/// Converts the signed numerator and denominator values
		/// to its equivalent string representation.
		/// A fraction (x/y) is returned when applicable.</summary>
		/// <param name="numer">The numeratior.</param>
		/// <param name="denom">The denominator.</param>
		/// <returns>A formatted Rational string.</returns>
		private static string ToRationalString(Int32 numer, Int32 denom) 
		{
			if (denom == 0) denom = 1;

			// Make the numerator "store" the sign
			if (denom < 0) 
			{
				numer = numer * -1;
				denom = denom * -1;
			}

			ReduceRational(ref numer, ref denom);

			string result;

			if (numer == 0) result = "0";
			else if (denom == 1) result = numer + "";
			else result = numer + "/" + denom;
    
			return result;
		}

		/// <summary>
		/// Reduces the rational number by dividing both the numerator
		/// and the denominator by their greatest common divisor.
		/// </summary>
		/// <param name="numer">The numeratior.</param>
		/// <param name="denom">The denominator.</param>
		private static void ReduceRational(ref Int32 numer, ref Int32 denom) 
		{
			if (numer != 0) 
			{
				Int32 common = GCD(Math.Abs(numer), denom);

				numer = numer / common;
				denom = denom / common;
			}
		}

		/// <summary>
		/// Computes and returns the greatest common divisor of the two
		/// positive parameters. Uses Euclid's algorithm.
		/// </summary>
		/// <param name="num1">First number.</param>
		/// <param name="num2">Second number.</param>
		/// <returns>The greated common denominator as a string.</returns>
		private static Int32 GCD(Int32 num1, Int32 num2) 
		{
			while (num1 != num2)
			{
				if (num1 > num2) num1 = num1 - num2;
				else num2 = num2 - num1;
			}

			return num1;
		}

		// //////////////////////////////////////////////////////////
		// Format an unsigned rational
		// //////////////////////////////////////////////////////////

		/// <summary>
		/// Converts the unsigned numerator and denominator values
		/// to its equivalent string representation.
		/// A fraction is used when applicable.
		/// </summary>
		/// <param name="numer">The numeratior.</param>
		/// <param name="denom">The denominator.</param>
		/// <returns>A formatted Rational string.</returns>
		private static string ToRationalString(UInt32 numer, UInt32 denom) 
		{
			if (denom == 0) denom = 1;

			ReduceRational(ref numer, ref denom);

			string result;

			if (numer == 0) result = "0";
			else if (denom == 1) result = numer + "";
			else result = numer + "/" + denom;
    
			return result;
		}

		/// <summary>
		/// Reduces the rational number by dividing both the numerator
		/// and the denominator by their greatest common divisor.
		/// </summary>
		/// <param name="numer">The numeratior.</param>
		/// <param name="denom">The denominator.</param>
		private static void ReduceRational(ref UInt32 numer, ref UInt32 denom) 
		{
			if (numer != 0) 
			{
				UInt32 common = GCD(numer, denom);

				numer = numer / common;
				denom = denom / common;
			}
		}

		/// <summary>
		/// Computes and returns the greatest common divisor of the two
		/// positive parameters. Uses Euclid's algorithm.
		/// </summary>
		/// <param name="num1">First number.</param>
		/// <param name="num2">Second number.</param>
		/// <returns>The greated common denominator as a string.</returns>
		private static UInt32 GCD(UInt32 num1, UInt32 num2) 
		{
			while (num1 != num2)
			{
				if (num1 > num2) num1 = num1 - num2;
				else num2 = num2 - num1;
			}

			return num1;
		}
		#endregion

		#region Special Formatting Operations

		/// <summary>The possible specialized formatting instruction 
		/// when reading an image's tag property value.</summary>
		public enum FormatInstruction 
		{
			/// <summary>No formatting instruction</summary>
			NO_OP,
			/// <summary>Instruction to change the value to a fraction.</summary>
			/// <remarks>This is only applicable to RATIONAL and SRATIONAL tags.</remarks>
			FRACTION,
			/// <summary>Instruction to change the value to a decimal.</summary>
			/// <remarks>This is only applicable to RATIONAL and SRATIONAL tags.</remarks>
			DECIMAL,
			/// <summary>Instruction to change the value to a date/time.</summary>
			/// <remarks>This is only applicable to ASCII tags.</remarks>
			DATETIME,
			/// <summary>Instruction to format the bytes as a non-null terminated string.</summary>
			/// <remarks>This is only applicable to UNDEFINED tags.</remarks>
			ALLCHAR,
			/// <summary>Instruction to format the bytes as a non-null terminated string.
			/// That can be encoded using either ASCII, JIS, Unicode or Undefined</summary>
			/// <remarks>This is only applicable to UNDEFINED tags.</remarks>
			USERCOMMENT,
			/// <summary>Instruction to format the bytes as a non-null terminated unicode string.
			/// </summary>
			UNICODE,
			/// <summary>Instruction to format the bytes as a Base-64 string.</summary>
			/// <remarks>This is only applicable to BYTE tags.</remarks>
			BASE64
		}

		public static FormatInstruction FindSpecialFormat(ExifProperty property)
		{
			switch(property)
			{
				case ExifProperty.ExposureTime:
					return FormatInstruction.FRACTION;

				case ExifProperty.ExifVersion:
				case ExifProperty.UserComment:
				case ExifProperty.FlashPixVersion:
					return FormatInstruction.ALLCHAR;

				case ExifProperty.FNumber:
				case ExifProperty.FocalLength:
					return FormatInstruction.DECIMAL;

				case ExifProperty.DateTime:
				case ExifProperty.DateTimeDigitized:
				case ExifProperty.DateTimeOriginal:
					return FormatInstruction.DATETIME;

				default:
					return FormatInstruction.NO_OP;
			}
		}

		#endregion

	}
}