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diff --git a/compiler/src/ItemProcessors.hs b/compiler/src/ItemProcessors.hs
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+-- ldgallery - A static generator which turns a collection of tagged
+--             pictures into a searchable web gallery.
+--
+-- Copyright (C) 2019-2022  Pacien TRAN-GIRARD
+--
+-- This program is free software: you can redistribute it and/or modify
+-- it under the terms of the GNU Affero General Public License as
+-- published by the Free Software Foundation, either version 3 of the
+-- License, or (at your option) any later version.
+--
+-- This program is distributed in the hope that it will be useful,
+-- but WITHOUT ANY WARRANTY; without even the implied warranty of
+-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+-- GNU Affero General Public License for more details.
+--
+-- You should have received a copy of the GNU Affero General Public License
+-- along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+module ItemProcessors
+  ( ItemProcessor
+  , itemFileProcessor
+  , thumbnailFileProcessor
+  ) where
+
+
+import Data.Char (toLower)
+import System.FilePath (takeExtension)
+
+import Config (Resolution(..))
+import Resource (ItemProcessor, Thumbnail(..), GalleryItemProps(..))
+import Caching (Cache)
+import FileProcessors
+import Files
+
+
+data Format =
+    PictureFormat
+  | PlainTextFormat
+  | MarkdownFormat
+  | PortableDocumentFormat
+  | EPUBFormat
+  | VideoFormat
+  | AudioFormat
+  | Unknown
+
+formatFromPath :: Path -> Format
+formatFromPath =
+  maybe Unknown ((fromExt . map toLower) . takeExtension) . fileName
+  where
+    fromExt :: String -> Format
+    fromExt ext = case ext of
+      ".bmp" -> PictureFormat
+      ".jpg" -> PictureFormat
+      ".jpeg" -> PictureFormat
+      ".png" -> PictureFormat
+      ".tiff" -> PictureFormat
+      ".hdr" -> PictureFormat
+      ".gif" -> PictureFormat
+      ".webp" -> PictureFormat
+      ".txt" -> PlainTextFormat
+      ".md" -> MarkdownFormat
+      ".pdf" -> PortableDocumentFormat
+      ".epub" -> EPUBFormat
+      ".wav" -> AudioFormat
+      ".oga" -> AudioFormat
+      ".ogg" -> AudioFormat
+      ".spx" -> AudioFormat
+      ".opus" -> AudioFormat
+      ".flac" -> AudioFormat
+      ".m4a" -> AudioFormat
+      ".mp3" -> AudioFormat
+      ".ogv" -> VideoFormat
+      ".ogx" -> VideoFormat
+      ".webm" -> VideoFormat
+      ".mkv" -> VideoFormat
+      ".mp4" -> VideoFormat
+      _ -> Unknown
+
+
+type ItemFileProcessor a =
+     FilePath -- ^ Filesystem input base path
+  -> FilePath -- ^ Filesystem output base path
+  -> FileName -- ^ Output class (subdir)
+  -> ItemProcessor a
+
+
+callFileProcessor :: (Path -> FileProcessor a) -> Cache a -> ItemFileProcessor a
+callFileProcessor processorProvider withCache inputBase outputBase resClass itemPath resPath =
+  withCache (processorProvider resPath)
+    itemPath
+    (resClass /> resPath)
+    (localPath $ inputBase /> resPath)
+    (localPath $ outputBase /> (resClass /> resPath))
+
+
+itemFileProcessor :: Maybe Resolution -> Cache GalleryItemProps -> ItemFileProcessor GalleryItemProps
+itemFileProcessor maxResolution =
+  callFileProcessor (flip processorFor maxResolution . formatFromPath)
+  where
+    processorFor :: Format -> Maybe Resolution -> FileProcessor GalleryItemProps
+    processorFor PictureFormat (Just maxRes) =
+      transformThenDescribe (resizePictureUpTo maxRes) getPictureProps
+    processorFor PictureFormat Nothing =
+      transformThenDescribe copyFileProcessor getPictureProps
+    processorFor PlainTextFormat _ = copyResource PlainText
+    processorFor MarkdownFormat _ = copyResource Markdown
+    processorFor PortableDocumentFormat _ = copyResource PDF
+    processorFor EPUBFormat _ = copyResource EPUB
+    processorFor VideoFormat _ = copyResource Video
+    processorFor AudioFormat _ = copyResource Audio
+    processorFor Unknown _ = copyResource Other
+    -- TODO: handle video reencoding and others?
+
+
+thumbnailFileProcessor :: Resolution -> Cache (Maybe Thumbnail) -> ItemFileProcessor (Maybe Thumbnail)
+thumbnailFileProcessor maxRes =
+  callFileProcessor (processorFor . formatFromPath)
+  where
+    processorFor :: Format -> FileProcessor (Maybe Thumbnail)
+    processorFor PictureFormat = transformThenDescribe (resizePictureUpTo maxRes) getThumbnailProps
+    processorFor _ = noopProcessor