Added --default-image-extension and readerDefaultImageExtension.

Note: Currently this only affects the markdown reader.

README

@@ -243,6 +243,11 @@ Reader options
     `perl,numberLines` or `haskell`. Multiple classes may be separated
     by spaces or commas.
 
+`--default-image-extension=`*EXTENSION*
+:   Specify a default extension to use when markdown image paths/URLs have no
+    extension.  This allows you to use the same markdown source for
+    formats that require different kinds of images.
+
 `--normalize`
 :   Normalize the document after reading:  merge adjacent
     `Str` or `Emph` elements, for example, and remove repeated `Space`s.

pandoc.hs

@@ -137,6 +137,7 @@ data Opt = Opt
     , optSetextHeaders     :: Bool       -- ^ Use atx headers for markdown level 1-2
     , optAscii             :: Bool       -- ^ Use ascii characters only in html
     , optTeXLigatures      :: Bool       -- ^ Use TeX ligatures for quotes/dashes
+    , optDefaultImageExtension :: String -- ^ Default image extension
     }
 
 -- | Defaults for command-line options.
@@ -192,6 +193,7 @@ defaultOpts = Opt
     , optSetextHeaders         = True
     , optAscii                 = False
     , optTeXLigatures          = True
+    , optDefaultImageExtension = ""
     }
 
 -- | A list of functions, each transforming the options data structure
@@ -495,6 +497,12 @@ options =
                   (\opt -> return opt { optSectionDivs = True }))
                  "" -- "Put sections in div tags in HTML"
 
+    , Option "" ["default-image-extension"]
+                 (ReqArg
+                  (\arg opt -> return opt { optDefaultImageExtension = arg })
+                   "extension")
+                  "" -- "Default extension for extensionless images"
+
     , Option "" ["email-obfuscation"]
                  (ReqArg
                   (\arg opt -> do
@@ -855,6 +863,7 @@ main = do
               , optSetextHeaders         = setextHeaders
               , optAscii                 = ascii
               , optTeXLigatures          = texLigatures
+              , optDefaultImageExtension = defaultImageExtension
              } = opts
 
   when dumpArgs $
@@ -996,6 +1005,7 @@ main = do
                       , readerCitationStyle = mbsty
                       , readerIndentedCodeClasses = codeBlockClasses
                       , readerApplyMacros = not laTeXOutput
+                      , readerDefaultImageExtension = defaultImageExtension
                       }
 
   let writerOptions = def { writerStandalone       = standalone',

src/Text/Pandoc/Options.hs

@@ -204,6 +204,7 @@ data ReaderOptions = ReaderOptions{
        , readerApplyMacros     :: Bool -- ^ Apply macros to TeX math
        , readerIndentedCodeClasses :: [String] -- ^ Default classes for
                                        -- indented code blocks
+       , readerDefaultImageExtension :: String -- ^ Default extension for images
 } deriving (Show, Read)
 
 instance Default ReaderOptions
@@ -220,6 +221,7 @@ instance Default ReaderOptions
                , readerCitationStyle         = Nothing
                , readerApplyMacros           = True
                , readerIndentedCodeClasses   = []
+               , readerDefaultImageExtension = ""
                }
 
 --

src/Text/Pandoc/Readers/Markdown.hs

@@ -51,6 +51,7 @@ import qualified Text.CSL as CSL
 import Data.Monoid (mconcat, mempty)
 import Control.Applicative ((<$>), (<*), (*>), (<$))
 import Control.Monad
+import System.FilePath (takeExtension, addExtension)
 import Text.HTML.TagSoup
 import Text.HTML.TagSoup.Match (tagOpen)
 import qualified Data.Set as Set
@@ -1561,7 +1562,11 @@ image :: MarkdownParser (F Inlines)
 image = try $ do
   char '!'
   (lab,raw) <- reference
-  regLink B.image lab <|> referenceLink B.image (lab,raw)
+  defaultExt <- getOption readerDefaultImageExtension
+  let constructor src = case takeExtension src of
+                              "" -> B.image (addExtension src defaultExt)
+                              _  -> B.image src
+  regLink constructor lab <|> referenceLink constructor (lab,raw)
 
 note :: MarkdownParser (F Inlines)
 note = try $ do