FindJPEG: Add version detection and associated test update and docs

Modules/FindJPEG.cmake

@@ -18,12 +18,16 @@
 #   where to find jpeglib.h, etc.
 # ``JPEG_LIBRARIES``
 #   the libraries needed to use JPEG.
+# ``JPEG_VERSION``
+#   the version of the JPEG library found
 #
 # Cache variables
 # ^^^^^^^^^^^^^^^
 #
 # The following cache variables may also be set:
 #
+# ``JPEG_INCLUDE_DIR``
+#   where to find jpeglib.h, etc.
 # ``JPEG_LIBRARY``
 #   where to find the JPEG library.
 
@@ -32,8 +36,29 @@ find_path(JPEG_INCLUDE_DIR jpeglib.h)
 set(JPEG_NAMES ${JPEG_NAMES} jpeg libjpeg)
 find_library(JPEG_LIBRARY NAMES ${JPEG_NAMES})
 
+if(JPEG_INCLUDE_DIR AND EXISTS "${JPEG_INCLUDE_DIR}/jpeglib.h")
+  file(STRINGS "${JPEG_INCLUDE_DIR}/jpeglib.h"
+    jpeg_lib_version REGEX "^#define[\t ]+JPEG_LIB_VERSION[\t ]+.*")
+
+  if (NOT jpeg_lib_version)
+    # libjpeg-turbo sticks JPEG_LIB_VERSION in jconfig.h
+    find_path(jconfig_dir jconfig.h)
+    if (jconfig_dir)
+      file(STRINGS "${jconfig_dir}/jconfig.h"
+        jpeg_lib_version REGEX "^#define[\t ]+JPEG_LIB_VERSION[\t ]+.*")
+    endif()
+    unset(jconfig_dir)
+  endif()
+
+  string(REGEX REPLACE "^#define[\t ]+JPEG_LIB_VERSION[\t ]+([0-9]+).*"
+    "\\1" JPEG_VERSION "${jpeg_lib_version}")
+  unset(jpeg_lib_version)
+endif()
+
 include(${CMAKE_CURRENT_LIST_DIR}/FindPackageHandleStandardArgs.cmake)
-find_package_handle_standard_args(JPEG DEFAULT_MSG JPEG_LIBRARY JPEG_INCLUDE_DIR)
+find_package_handle_standard_args(JPEG
+  REQUIRED_VARS JPEG_LIBRARY JPEG_INCLUDE_DIR
+  VERSION_VAR JPEG_VERSION)
 
 if(JPEG_FOUND)
   set(JPEG_LIBRARIES ${JPEG_LIBRARY})

Tests/CMakeOnly/AllFindModules/CMakeLists.txt

@@ -86,7 +86,7 @@ foreach(VTEST ALSA ARMADILLO BZIP2 CUPS CURL EXPAT FREETYPE GETTEXT GIT HG
 endforeach()
 
 foreach(VTEST BISON Boost CUDA DOXYGEN FLEX GIF GTK2
-        HDF5 LibArchive OPENSCENEGRAPH RUBY SWIG Protobuf)
+        HDF5 JPEG LibArchive OPENSCENEGRAPH RUBY SWIG Protobuf)
     check_version_string(${VTEST} ${VTEST}_VERSION)
 endforeach()