Gallery Server Pro - An ASP.NET Gallery for Sharing Photos, Video, Audio and Other Media

using System;
using System.Diagnostics;
using System.Text;
using GalleryServerPro.ErrorHandler.CustomExceptions;

namespace GalleryServerPro.Business
{
	/// <summary>
	/// Contains functionality for interacting with ImageMagick, the open source utility. Specifically, Gallery Server Pro uses it to generate
	/// thumbnail images for .eps and .pdf files. See http://www.imagemagick.org for more information.
	/// </summary>
	/// <remarks>Requires Visual C++ 2008 Redistributable Package (x86). 64-bit OS requires both x86 and x64 versions. These are installed with
	/// .NET 3.5 but I am not sure about .NET 4.0.
	/// To read .eps and .pdf files, GhostScript must be installed on the server.</remarks>
	public class ImageMagick
	{
		private StringBuilder _sbOutput;
		private StringBuilder _sbError;

		/// <summary>
		/// Generates a thumbnail image for the media file at the specified <paramref name="mediaFilePath" /> and returns the output from the
		/// execution of the convert utility. The thumbnail is saved to 
		/// <paramref name="thumbnailFilePath" />. The <paramref name="galleryId" /> is used during error handling to associate the error,
		/// if any, with the gallery. Requires the application to be running at Full Trust and GhostScript to be installed on the server. Returns <see cref="String.Empty" /> when the 
		/// application is running at less than Full Trust or when the convert utility is not present in the bin directory.
		/// </summary>
		/// <param name="mediaFilePath">The full file path to the source media file. Example: D:\media\myfile.eps</param>
		/// <param name="thumbnailFilePath">The full file path to store the thumbnail image to. If a file with this name is already present,
		/// it is overwritten.</param>
		/// <param name="galleryId">The gallery ID.</param>
		/// <returns>Returns the text output from the execution of the convert.exe utility.</returns>
		public static string GenerateThumbnail(string mediaFilePath, string thumbnailFilePath, int galleryId)
		{
			string convertOutput = String.Empty;

			if ((AppSetting.Instance.AppTrustLevel != ApplicationTrustLevel.Full) || (String.IsNullOrEmpty(AppSetting.Instance.ImageMagickConvertPath)))
			{
				return convertOutput;
			}

			// Create arguments. The [0] tells it to generate one image from the first page for PDF files (otherwise we get one image for every page)
			// Example: "D:\media\pic.eps[0]" "D:\media\pic.jpg"
			string args = string.Format(@"""{0}[0]"" ""{1}""", mediaFilePath, thumbnailFilePath);

			ImageMagick imageMagick = new ImageMagick();
			convertOutput = imageMagick.ExecuteConvert(args, galleryId);

			if (!String.IsNullOrEmpty(convertOutput))
			{
				// The utility returns an empty string when it is successful, so something went wrong. Log it.
				ErrorHandler.Error.Record(new BusinessException(convertOutput), galleryId, Factory.LoadGallerySettings(), AppSetting.Instance);
			}

			return convertOutput;
		}

		/// <summary>
		/// Execute the ImageMagick convert.exe utility with the given <paramref name="arguments" /> and return the text output generated by it.
		/// See http://www.imagemagick.org for documentation.
		/// </summary>
		/// <param name="arguments">The argument values to pass to the ImageMagick convert.exe utility. 
		/// Example: -density 300 "D:\media\myimage.eps[0]" "D:\media\zThumb_myimage.jpg"</param>
		/// <param name="galleryId">The gallery ID.</param>
		/// <returns>Returns the text output from the execution of the convert.exe utility.</returns>
		private string ExecuteConvert(string arguments, int galleryId)
		{
			ProcessStartInfo info = new ProcessStartInfo(AppSetting.Instance.ImageMagickConvertPath, arguments);
			info.UseShellExecute = false;
			info.CreateNoWindow = true;
			info.RedirectStandardError = true;
			info.RedirectStandardInput = true;
			info.RedirectStandardOutput = true;

			using (Process p = new Process())
			{
				try
				{
					_sbOutput = new StringBuilder();
					_sbError = new StringBuilder();

					p.StartInfo = info;
					p.OutputDataReceived += new DataReceivedEventHandler(Convert__OutputDataReceived);
					p.ErrorDataReceived += new DataReceivedEventHandler(Convert_ErrorDataReceived);

					p.Start();

					p.BeginOutputReadLine();
					p.BeginErrorReadLine();

					p.WaitForExit();
					p.Close();
				}
				catch (Exception ex)
				{
					ErrorHandler.Error.Record(ex, galleryId, Factory.LoadGallerySettings(), AppSetting.Instance);
				}
			}

			// If we have error data, append it to the output string.
			if (_sbError.Length > 0)
			{
				_sbOutput.Append(_sbError.ToString());
			}

			// Return the output from the utility.
			return _sbOutput.ToString();
		}

		void Convert_ErrorDataReceived(object sender, DataReceivedEventArgs e)
		{
			if (!String.IsNullOrEmpty(e.Data))
			{
				_sbError.AppendLine(e.Data);
			}
		}

		void Convert__OutputDataReceived(object sender, DataReceivedEventArgs e)
		{
			if (!String.IsNullOrEmpty(e.Data))
			{
				_sbOutput.AppendLine(e.Data);
			}
		}
	}
}