ImageThumbnailCreator.cs

using System;
using System.IO;
using System.Windows.Media.Imaging;
using GalleryServerPro.Business.Interfaces;
using GalleryServerPro.Events.CustomExceptions;

namespace GalleryServerPro.Business
{
	/// <summary>
	/// Provides functionality for creating and saving the thumbnail image files associated with <see cref="Image" /> gallery objects.
	/// </summary>
	public class ImageThumbnailCreator : DisplayObjectCreator
	{
		/// <summary>
		/// Initializes a new instance of the <see cref="ImageThumbnailCreator"/> class.
		/// </summary>
		/// <param name="imageObject">The image object.</param>
		public ImageThumbnailCreator(Image imageObject)
		{
			this.GalleryObject = imageObject;
		}

		/// <summary>
		/// Generate the file for this display object and save it to the file system. The routine may decide that
		/// a file does not need to be generated, usually because it already exists. However, it will always be
		/// created if the relevant flag is set on the parent IGalleryObject. (Example: If
		/// <see cref="IGalleryObject.RegenerateThumbnailOnSave" /> = true, the thumbnail file will 
		/// always be created.) No data is persisted to the data store.
		/// </summary>
		/// <exception cref="UnsupportedImageTypeException">Thrown when Gallery Server Pro cannot process the image, 
		/// most likely because it is corrupt or an unsupported image type.</exception>
		public override void GenerateAndSaveFile()
		{
			// If necessary, generate and save the thumbnail version of the original image.
			if (!(IsThumbnailImageRequired()))
			{
				return; // No thumbnail image required.
			}

			var gallerySetting = GallerySettings;

			// Determine file name and path of the thumbnail image. If a file name has already been previously
			// calculated for this media object, re-use it. Otherwise generate a unique name.
			var newFilename = GalleryObject.Thumbnail.FileName;
			var newFilePath = GalleryObject.Thumbnail.FileNamePhysicalPath;

			if (String.IsNullOrEmpty(newFilename))
			{
				var thumbnailPath = HelperFunctions.MapAlbumDirectoryStructureToAlternateDirectory(this.GalleryObject.Original.FileInfo.DirectoryName, gallerySetting.FullThumbnailPath, gallerySetting.FullMediaObjectPath);
				newFilename = GenerateJpegFilename(thumbnailPath, gallerySetting.ThumbnailFileNamePrefix);
				newFilePath = Path.Combine(thumbnailPath, newFilename);
			}

			var imageCreated = false;

			var size = System.Windows.Size.Empty;
			if (Array.IndexOf<string>(gallerySetting.ImageMagickFileTypes, Path.GetExtension(GalleryObject.Original.FileName).ToLowerInvariant()) >= 0)
			{
				size = GenerateImageUsingImageMagick(newFilePath, gallerySetting.MaxThumbnailLength, gallerySetting.ThumbnailImageJpegQuality);

				imageCreated = !size.IsEmpty;
			}

			if (!imageCreated)
			{
				size = GenerateImageUsingDotNet(newFilePath, gallerySetting.MaxThumbnailLength, gallerySetting.ThumbnailImageJpegQuality);
			}

			if (!size.IsEmpty)
			{
				GalleryObject.Thumbnail.Width = (int)size.Width;
				GalleryObject.Thumbnail.Height = (int)size.Height;
			}

			GalleryObject.Thumbnail.FileName = newFilename;
			GalleryObject.Thumbnail.FileNamePhysicalPath = newFilePath;

			int fileSize = (int)(GalleryObject.Thumbnail.FileInfo.Length / 1024);

			GalleryObject.Thumbnail.FileSizeKB = (fileSize < 1 ? 1 : fileSize); // Very small files should be 1, not 0.
		}

		private bool IsThumbnailImageRequired()
		{
			// We must create a thumbnail image in the following circumstances:
			// 1. The file corresponding to a previously created thumbnail image file does not exist.
			//    OR
			// 2. The overwrite flag is true.
			//    OR
			// 3. There is a request to rotate the image.

			bool thumbnailImageMissing = IsThumbnailImageFileMissing(); // Test 1

			bool overwriteFlag = GalleryObject.RegenerateThumbnailOnSave; // Test 2

			bool rotateIsRequested = (GalleryObject.Rotation != MediaObjectRotation.NotSpecified);

			return (thumbnailImageMissing || overwriteFlag || rotateIsRequested);
		}

		private bool IsThumbnailImageFileMissing()
		{
			// Does the thumbnail image file exist? (Maybe it was accidentally deleted or moved by the user,
			// or maybe it's a new object.)
			bool thumbnailImageExists = false;
			if (File.Exists(GalleryObject.Thumbnail.FileNamePhysicalPath))
			{
				// Thumbnail image file exists.
				thumbnailImageExists = true;
			}

			bool thumbnailImageIsMissing = !thumbnailImageExists;

			return thumbnailImageIsMissing;
		}
	}
}