Added `--default-image-extension` and `readerDefaultImageExtension`.

Note: Currently this only affects the markdown reader.

4 files changed, 134 insertions, 112 deletions

diff --git a/README b/README
index 20581b26a..cdb5a1226 100644
--- a/README
+++ b/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.
diff --git a/pandoc.hs b/pandoc.hs
index 2b6ed3a46..dc7de52a8 100644
--- a/pandoc.hs
+++ b/pandoc.hs
@@ -137,61 +137,63 @@ 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.
 defaultOpts :: Opt
 defaultOpts = Opt
-    { optTabStop           = 4
-    , optPreserveTabs      = False
-    , optStandalone        = False
-    , optReader            = ""    -- null for default reader
-    , optWriter            = ""    -- null for default writer
-    , optParseRaw          = False
-    , optTableOfContents   = False
-    , optTransforms        = []
-    , optTemplate          = Nothing
-    , optVariables         = []
-    , optOutputFile        = "-"    -- "-" means stdout
-    , optNumberSections    = False
-    , optSectionDivs       = False
-    , optIncremental       = False
-    , optSelfContained     = False
-    , optSmart             = False
-    , optOldDashes         = False
-    , optHtml5             = False
-    , optHtmlQTags         = False
-    , optHighlight         = True
-    , optHighlightStyle    = pygments
-    , optChapters          = False
-    , optHTMLMathMethod    = PlainMath
-    , optReferenceODT      = Nothing
-    , optReferenceDocx     = Nothing
-    , optEpubStylesheet    = Nothing
-    , optEpubMetadata      = ""
-    , optEpubFonts         = []
-    , optEpubChapterLevel  = 1
-    , optTOCDepth          = 3
-    , optDumpArgs          = False
-    , optIgnoreArgs        = False
-    , optReferenceLinks    = False
-    , optWrapText          = True
-    , optColumns           = 72
-    , optPlugins           = []
-    , optEmailObfuscation  = JavascriptObfuscation
-    , optIdentifierPrefix  = ""
-    , optIndentedCodeClasses = []
-    , optDataDir           = Nothing
-    , optCiteMethod        = Citeproc
-    , optBibliography      = []
-    , optCslFile           = Nothing
-    , optAbbrevsFile       = Nothing
-    , optListings          = False
-    , optLaTeXEngine       = "pdflatex"
-    , optSlideLevel        = Nothing
-    , optSetextHeaders     = True
-    , optAscii             = False
-    , optTeXLigatures      = True
+    { optTabStop               = 4
+    , optPreserveTabs          = False
+    , optStandalone            = False
+    , optReader                = ""    -- null for default reader
+    , optWriter                = ""    -- null for default writer
+    , optParseRaw              = False
+    , optTableOfContents       = False
+    , optTransforms            = []
+    , optTemplate              = Nothing
+    , optVariables             = []
+    , optOutputFile            = "-"    -- "-" means stdout
+    , optNumberSections        = False
+    , optSectionDivs           = False
+    , optIncremental           = False
+    , optSelfContained         = False
+    , optSmart                 = False
+    , optOldDashes             = False
+    , optHtml5                 = False
+    , optHtmlQTags             = False
+    , optHighlight             = True
+    , optHighlightStyle        = pygments
+    , optChapters              = False
+    , optHTMLMathMethod        = PlainMath
+    , optReferenceODT          = Nothing
+    , optReferenceDocx         = Nothing
+    , optEpubStylesheet        = Nothing
+    , optEpubMetadata          = ""
+    , optEpubFonts             = []
+    , optEpubChapterLevel      = 1
+    , optTOCDepth              = 3
+    , optDumpArgs              = False
+    , optIgnoreArgs            = False
+    , optReferenceLinks        = False
+    , optWrapText              = True
+    , optColumns               = 72
+    , optPlugins               = []
+    , optEmailObfuscation      = JavascriptObfuscation
+    , optIdentifierPrefix      = ""
+    , optIndentedCodeClasses   = []
+    , optDataDir               = Nothing
+    , optCiteMethod            = Citeproc
+    , optBibliography          = []
+    , optCslFile               = Nothing
+    , optAbbrevsFile           = Nothing
+    , optListings              = False
+    , optLaTeXEngine           = "pdflatex"
+    , optSlideLevel            = Nothing
+    , 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
@@ -806,55 +814,56 @@ main = do
   -- thread option data structure through all supplied option actions
   opts <- foldl (>>=) (return defaultOpts') actions
 
-  let Opt    {  optTabStop           = tabStop
-              , optPreserveTabs      = preserveTabs
-              , optStandalone        = standalone
-              , optReader            = readerName
-              , optWriter            = writerName
-              , optParseRaw          = parseRaw
-              , optVariables         = variables
-              , optTableOfContents   = toc
-              , optTransforms        = transforms
-              , optTemplate          = templatePath
-              , optOutputFile        = outputFile
-              , optNumberSections    = numberSections
-              , optSectionDivs       = sectionDivs
-              , optIncremental       = incremental
-              , optSelfContained     = selfContained
-              , optSmart             = smart
-              , optOldDashes         = oldDashes
-              , optHtml5             = html5
-              , optHtmlQTags         = htmlQTags
-              , optHighlight         = highlight
-              , optHighlightStyle    = highlightStyle
-              , optChapters          = chapters
-              , optHTMLMathMethod    = mathMethod
-              , optReferenceODT      = referenceODT
-              , optReferenceDocx     = referenceDocx
-              , optEpubStylesheet    = epubStylesheet
-              , optEpubMetadata      = epubMetadata
-              , optEpubFonts         = epubFonts
-              , optEpubChapterLevel  = epubChapterLevel
-              , optTOCDepth          = epubTOCDepth
-              , optDumpArgs          = dumpArgs
-              , optIgnoreArgs        = ignoreArgs
-              , optReferenceLinks    = referenceLinks
-              , optWrapText          = wrap
-              , optColumns           = columns
-              , optEmailObfuscation  = obfuscationMethod
-              , optIdentifierPrefix  = idPrefix
-              , optIndentedCodeClasses = codeBlockClasses
-              , optDataDir           = mbDataDir
-              , optBibliography      = reffiles
-              , optCslFile           = mbCsl
-              , optAbbrevsFile       = cslabbrevs
-              , optCiteMethod        = citeMethod
-              , optListings          = listings
-              , optLaTeXEngine       = latexEngine
-              , optSlideLevel        = slideLevel
-              , optSetextHeaders     = setextHeaders
-              , optAscii             = ascii
-              , optTeXLigatures      = texLigatures
+  let Opt    {  optTabStop               = tabStop
+              , optPreserveTabs          = preserveTabs
+              , optStandalone            = standalone
+              , optReader                = readerName
+              , optWriter                = writerName
+              , optParseRaw              = parseRaw
+              , optVariables             = variables
+              , optTableOfContents       = toc
+              , optTransforms            = transforms
+              , optTemplate              = templatePath
+              , optOutputFile            = outputFile
+              , optNumberSections        = numberSections
+              , optSectionDivs           = sectionDivs
+              , optIncremental           = incremental
+              , optSelfContained         = selfContained
+              , optSmart                 = smart
+              , optOldDashes             = oldDashes
+              , optHtml5                 = html5
+              , optHtmlQTags             = htmlQTags
+              , optHighlight             = highlight
+              , optHighlightStyle        = highlightStyle
+              , optChapters              = chapters
+              , optHTMLMathMethod        = mathMethod
+              , optReferenceODT          = referenceODT
+              , optReferenceDocx         = referenceDocx
+              , optEpubStylesheet        = epubStylesheet
+              , optEpubMetadata          = epubMetadata
+              , optEpubFonts             = epubFonts
+              , optEpubChapterLevel      = epubChapterLevel
+              , optTOCDepth              = epubTOCDepth
+              , optDumpArgs              = dumpArgs
+              , optIgnoreArgs            = ignoreArgs
+              , optReferenceLinks        = referenceLinks
+              , optWrapText              = wrap
+              , optColumns               = columns
+              , optEmailObfuscation      = obfuscationMethod
+              , optIdentifierPrefix      = idPrefix
+              , optIndentedCodeClasses   = codeBlockClasses
+              , optDataDir               = mbDataDir
+              , optBibliography          = reffiles
+              , optCslFile               = mbCsl
+              , optAbbrevsFile           = cslabbrevs
+              , optCiteMethod            = citeMethod
+              , optListings              = listings
+              , optLaTeXEngine           = latexEngine
+              , optSlideLevel            = slideLevel
+              , 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',
diff --git a/src/Text/Pandoc/Options.hs b/src/Text/Pandoc/Options.hs
index f67debf97..1ba8a6dd6 100644
--- a/src/Text/Pandoc/Options.hs
+++ b/src/Text/Pandoc/Options.hs
@@ -204,22 +204,24 @@ 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
   where def = ReaderOptions{
-                 readerExtensions          = pandocExtensions
-               , readerSmart               = False
-               , readerStrict              = False
-               , readerStandalone          = False
-               , readerParseRaw            = False
-               , readerColumns             = 80
-               , readerTabStop             = 4
-               , readerOldDashes           = False
-               , readerReferences          = []
-               , readerCitationStyle       = Nothing
-               , readerApplyMacros         = True
-               , readerIndentedCodeClasses = []
+                 readerExtensions            = pandocExtensions
+               , readerSmart                 = False
+               , readerStrict                = False
+               , readerStandalone            = False
+               , readerParseRaw              = False
+               , readerColumns               = 80
+               , readerTabStop               = 4
+               , readerOldDashes             = False
+               , readerReferences            = []
+               , readerCitationStyle         = Nothing
+               , readerApplyMacros           = True
+               , readerIndentedCodeClasses   = []
+               , readerDefaultImageExtension = ""
                }
 
 --
diff --git a/src/Text/Pandoc/Readers/Markdown.hs b/src/Text/Pandoc/Readers/Markdown.hs
index dc30e17ed..6b144f35e 100644
--- a/src/Text/Pandoc/Readers/Markdown.hs
+++ b/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