configure.ac, app: require liblcms2 >= 2.7

and add an lcms2 runtime version check to app/sanity.c

Fixes:
Bug 736701 - LCMS2 rounding errors cause problems with certain GIMP blend modes

app/Makefile.am

@@ -118,6 +118,7 @@ AM_CPPFLAGS = \
 	$(GTK_CFLAGS)			\
 	$(PANGOCAIRO_CFLAGS)		\
 	$(GEGL_CFLAGS)			\
+	$(LCMS_CFLAGS)			\
 	$(GEXIV2_CFLAGS)		\
 	-I$(includedir)			\
 	-I$(builddir)/gui
@@ -163,6 +164,7 @@ gimpconsoleldadd = \
 	$(GIO_WINDOWS_LIBS)		\
 	$(GEGL_LIBS)			\
 	$(GLIB_LIBS)			\
+	$(LCMS_LIBS)			\
 	$(GEXIV2_LIBS)			\
 	$(Z_LIBS)			\
 	$(JSON_C_LIBS)			\

app/sanity.c

@@ -22,6 +22,7 @@
 #include <pango/pango.h>
 #include <pango/pangoft2.h>
 #include <gdk-pixbuf/gdk-pixbuf.h>
+#include <lcms2.h>
 #include <gexiv2/gexiv2.h>
 #include <gegl.h>
 
@@ -39,6 +40,7 @@ static gchar * sanity_check_pango             (void);
 static gchar * sanity_check_fontconfig        (void);
 static gchar * sanity_check_freetype          (void);
 static gchar * sanity_check_gdk_pixbuf        (void);
+static gchar * sanity_check_lcms              (void);
 static gchar * sanity_check_gexiv2            (void);
 static gchar * sanity_check_babl              (void);
 static gchar * sanity_check_gegl              (void);
@@ -71,6 +73,9 @@ sanity_check (void)
   if (! abort_message)
     abort_message = sanity_check_gdk_pixbuf ();
 
+  if (! abort_message)
+    abort_message = sanity_check_lcms ();
+
   if (! abort_message)
     abort_message = sanity_check_gexiv2 ();
 
@@ -351,6 +356,54 @@ sanity_check_gdk_pixbuf (void)
   return NULL;
 }
 
+static gchar *
+sanity_check_lcms (void)
+{
+#define LCMS_REQUIRED_MAJOR 2
+#define LCMS_REQUIRED_MINOR 7
+
+  gint lcms_version = cmsGetEncodedCMMversion ();
+
+  if (LCMS_VERSION > lcms_version)
+    {
+      return g_strdup_printf
+        ("Liblcms2 version mismatch!\n\n"
+         "GIMP was compiled against LittleCMS version %d.%d, but the\n"
+         "LittleCMS version found at runtime is only %d.%d.\n\n"
+         "Somehow you or your software packager managed\n"
+         "to install a LittleCMS that is older than what GIMP was\n"
+         "built against.\n\n"
+         "Please make sure that the installed LittleCMS version\n"
+         "is at least %d.%d and that headers and library match.",
+         LCMS_VERSION / 1000, LCMS_VERSION % 100 / 10,
+         lcms_version / 1000, lcms_version % 100 / 10,
+         LCMS_VERSION / 1000, LCMS_VERSION % 100 / 10);
+    }
+
+  if (lcms_version < (LCMS_REQUIRED_MAJOR * 1000 +
+                      LCMS_REQUIRED_MINOR * 10))
+    {
+      const gint lcms_major_version = lcms_version / 1000;
+      const gint lcms_minor_version = lcms_version % 100 / 10;
+
+      return g_strdup_printf
+        ("Liblcms2 version too old!\n\n"
+         "GIMP requires LittleCMS version %d.%d or later.\n"
+         "Installed LittleCMS version is %d.%d.\n\n"
+         "Somehow you or your software packager managed\n"
+         "to install GIMP with an older LittleCMS version.\n\n"
+         "Please upgrade to LittleCMS version %d.%d or later.",
+         LCMS_REQUIRED_MAJOR, LCMS_REQUIRED_MINOR,
+         lcms_major_version, lcms_minor_version,
+         LCMS_REQUIRED_MAJOR, LCMS_REQUIRED_MINOR);
+    }
+
+#undef LCMS_REQUIRED_MAJOR
+#undef LCMS_REQUIRED_MINOR
+
+  return NULL;
+}
+
 static gchar *
 sanity_check_gexiv2 (void)
 {

configure.ac

@@ -68,7 +68,7 @@ m4_define([poppler_data_required_version], [0.4.7])
 m4_define([libgudev_required_version], [167])
 m4_define([gexiv2_required_version], [0.6.1])
 m4_define([libmypaint_required_version], [1.3.0])
-m4_define([lcms_required_version], [2.6])
+m4_define([lcms_required_version], [2.7])
 m4_define([libpng_required_version], [1.2.37])
 m4_define([liblzma_required_version], [5.0.0])
 m4_define([openexr_required_version], [1.6.1])