Lua: add new module pandoc.image

The module provides basic querying functions for image properties.

pandoc-lua-engine/pandoc-lua-engine.cabal

@@ -74,6 +74,7 @@ library
                      , Text.Pandoc.Lua.Marshal.CommonState
                      , Text.Pandoc.Lua.Marshal.Context
                      , Text.Pandoc.Lua.Marshal.Format
+                     , Text.Pandoc.Lua.Marshal.ImageSize
                      , Text.Pandoc.Lua.Marshal.PandocError
                      , Text.Pandoc.Lua.Marshal.ReaderOptions
                      , Text.Pandoc.Lua.Marshal.Reference
@@ -82,6 +83,7 @@ library
                      , Text.Pandoc.Lua.Marshal.WriterOptions
                      , Text.Pandoc.Lua.Module.CLI
                      , Text.Pandoc.Lua.Module.Format
+                     , Text.Pandoc.Lua.Module.Image
                      , Text.Pandoc.Lua.Module.JSON
                      , Text.Pandoc.Lua.Module.MediaBag
                      , Text.Pandoc.Lua.Module.Pandoc

pandoc-lua-engine/src/Text/Pandoc/Lua/Init.hs

@@ -41,6 +41,7 @@ import qualified HsLua.Module.Path as Module.Path
 import qualified HsLua.Module.Zip as Module.Zip
 import qualified Text.Pandoc.Lua.Module.CLI as Pandoc.CLI
 import qualified Text.Pandoc.Lua.Module.Format as Pandoc.Format
+import qualified Text.Pandoc.Lua.Module.Image as Pandoc.Image
 import qualified Text.Pandoc.Lua.Module.JSON as Pandoc.JSON
 import qualified Text.Pandoc.Lua.Module.MediaBag as Pandoc.MediaBag
 import qualified Text.Pandoc.Lua.Module.Pandoc as Module.Pandoc
@@ -91,6 +92,7 @@ loadedModules :: [Module PandocError]
 loadedModules =
   [ Pandoc.CLI.documentedModule
   , Pandoc.Format.documentedModule
+  , Pandoc.Image.documentedModule
   , Pandoc.JSON.documentedModule
   , Pandoc.MediaBag.documentedModule
   , Pandoc.Scaffolding.documentedModule

pandoc-lua-engine/src/Text/Pandoc/Lua/Marshal/ImageSize.hs

@@ -0,0 +1,31 @@
+{-# LANGUAGE LambdaCase           #-}
+{-# LANGUAGE OverloadedStrings    #-}
+{- |
+   Module      : Text.Pandoc.Lua.Marshal.ImageSize
+   Copyright   : © 2024 Albert Krewinkel
+   License     : GPL-2.0-or-later
+   Maintainer  : Albert Krewinkel <[email protected]>
+
+Marshaling image properties.
+-}
+module Text.Pandoc.Lua.Marshal.ImageSize
+  ( pushImageType
+  , pushImageSize
+  ) where
+
+import Data.Char (toLower)
+import HsLua
+import Text.Pandoc.ImageSize
+
+-- | Pushes an 'ImageType' as a string value.
+pushImageType :: LuaError e => Pusher e ImageType
+pushImageType = pushString . map toLower . show
+
+-- | Pushes a dimensional value.
+pushImageSize :: LuaError e => Pusher e ImageSize
+pushImageSize = pushAsTable
+  [ ("width", pushIntegral . pxX)
+  , ("height", pushIntegral . pxY)
+  , ("dpi_horz", pushIntegral . dpiX)
+  , ("dpi_vert", pushIntegral . dpiY)
+  ]

pandoc-lua-engine/src/Text/Pandoc/Lua/Module/Image.hs

@@ -0,0 +1,99 @@
+{-# LANGUAGE OverloadedStrings #-}
+{-|
+Module      : Text.Pandoc.Lua.Module.Image
+Copyright   : © 2024 Albert Krewinkel
+License     : MIT
+Maintainer  : Albert Krewinkel <[email protected]>
+
+Lua module for basic image operations.
+-}
+module Text.Pandoc.Lua.Module.Image (
+  -- * Module
+    documentedModule
+
+  -- ** Functions
+  , size
+  , format
+  )
+where
+
+import Prelude hiding (null)
+import Data.Default (Default (def))
+import Data.Maybe (fromMaybe)
+import Data.Version (makeVersion)
+import HsLua.Core
+import HsLua.Marshalling
+import HsLua.Packaging
+import Text.Pandoc.Error (PandocError)
+import Text.Pandoc.ImageSize (imageType, imageSize)
+import Text.Pandoc.Lua.PandocLua ()
+import Text.Pandoc.Lua.Marshal.ImageSize (pushImageType, pushImageSize)
+import Text.Pandoc.Lua.Marshal.WriterOptions (peekWriterOptions)
+
+import qualified Data.Text as T
+
+-- | The @aeson@ module specification.
+documentedModule :: Module PandocError
+documentedModule = Module
+  { moduleName = "pandoc.image"
+  , moduleDescription = "Basic image querying functions."
+  , moduleFields = fields
+  , moduleFunctions = functions
+  , moduleOperations = []
+  , moduleTypeInitializers = []
+  }
+
+--
+-- Fields
+--
+
+-- | Exported fields.
+fields :: LuaError e => [Field e]
+fields = []
+
+--
+-- Functions
+--
+
+functions :: [DocumentedFunction PandocError]
+functions =
+  [ size `since` makeVersion [3, 2, 0]
+  , format `since` makeVersion [3, 2, 0]
+  ]
+
+-- | Decode a JSON string into a Lua object.
+size :: DocumentedFunction PandocError
+size = defun "size"
+  ### liftPure2
+      (\img mwriterOpts -> imageSize (fromMaybe def mwriterOpts) img)
+  <#> parameter peekByteString "string" "image" "image data"
+  <#> opt (parameter peekWriterOptions "WriterOptions" "writer_options"
+            "writer options")
+  =#> functionResult (either (failLua . T.unpack) pushImageSize) "string|table"
+        "image size object or error message"
+  -- #? T.unlines
+  --    [ "Creates a Lua object from a JSON string. The function returns an"
+  --    , "[[Inline]], [[Block]], [[Pandoc]], [[Inlines]], or [[Blocks]] element"
+  --    , "if the input can be decoded into represent any of those types."
+  --    , "Otherwise the default decoding is applied, using tables, booleans,"
+  --    , "numbers, and [null](#pandoc.json.null) to represent the JSON value."
+  --    , ""
+  --    , "The special handling of AST elements can be disabled by setting"
+  --    , "`pandoc_types` to `false`."
+  --    ]
+
+-- | Encode a Lua object as JSON.
+format :: LuaError e => DocumentedFunction e
+format = defun "format"
+  ### liftPure imageType
+  <#> parameter peekByteString "string" "image" "binary image data"
+  =#> functionResult (maybe pushnil pushImageType) "string|nil"
+        "image format, or nil if the format cannot be determined"
+  -- #? T.unlines
+  --    ["Encodes a Lua object as JSON string."
+  --    , ""
+  --    , "If the object has a metamethod with name `__tojson`, then the"
+  --    , "result is that of a call to that method with `object` passed as"
+  --    , "the sole argument. The result of that call is expected to be a"
+  --    , "valid JSON string, but this not checked."
+  --    ]

pandoc-lua-engine/test/Tests/Lua/Module.hs

@@ -25,6 +25,8 @@ tests =
                   ("lua" </> "module" </> "pandoc-list.lua")
   , testPandocLua "pandoc.format"
                   ("lua" </> "module" </> "pandoc-format.lua")
+  , testPandocLua "pandoc.image"
+                  ("lua" </> "module" </> "pandoc-image.lua")
   , testPandocLua "pandoc.json"
                   ("lua" </> "module" </> "pandoc-json.lua")
   , testPandocLua "pandoc.mediabag"

pandoc-lua-engine/test/lua/module/pandoc-image.lua

@@ -0,0 +1,59 @@
+--
+-- Tests for the system module
+--
+local image = require 'pandoc.image'
+local tasty = require 'tasty'
+
+local group = tasty.test_group
+local test = tasty.test_case
+local assert = tasty.assert
+
+local svg_image = [==[<?xml version="1.0"?>
+<svg xmlns="http://www.w3.org/2000/svg"
+     xmlns:xlink="http://www.w3.org/1999/xlink"
+     height="70" width="70"
+     viewBox="-35 -35 70 70">
+  <title>test</title>
+  <!-- document shape -->
+  <polygon points="-10,-31.53 -10,-3.25 0,0 10,-3.25 10,-23.53 2,-31.53" />
+</svg>
+]==]
+
+return {
+  -- Check existence of static fields
+  group 'static fields' {
+  },
+
+  group 'size' {
+    test('string', function ()
+      local imgsize = {
+        width = 70,
+        height = 70,
+        dpi_horz = 96,
+        dpi_vert = 96,
+      }
+      assert.are_same(image.size(svg_image), imgsize)
+    end),
+    test('fails on faulty eps', function ()
+      assert.error_matches(
+        function () image.size('%!PS EPSF') end,
+        'could not determine EPS size'
+      )
+    end),
+    test('fails if input is not an image', function ()
+      assert.error_matches(
+        function () image.size('not an image') end,
+        'could not determine image type'
+      )
+    end),
+               },
+
+  group 'format' {
+    test('SVG', function ()
+           assert.are_equal(image.format(svg_image), 'svg')
+    end),
+    test('returns nil if input is not an image', function ()
+      assert.is_nil(image.format('not an image'))
+    end),
+  },
+}