[gegl] tools: port exp_combine to use gexiv2 instead of exiv2 directly

[Øyvind "pippin" Kolås <ok src gnome org>]

commit 0703b6b38f4e6cf8ecc623c09c05ef73c6424ee4
Author: Øyvind Kolås <pippin gimp org>
Date:   Tue Mar 12 21:58:13 2019 +0100

    tools: port exp_combine to use gexiv2 instead of exiv2 directly
    
    We already rely on gexiv2, and recent updates of exiv2 broke API this
    commandline tool was reliant on.

 tools/Makefile.am     |  6 +++---
 tools/exp_combine.cpp | 42 +++++++++++++++++++-----------------------
 2 files changed, 22 insertions(+), 26 deletions(-)
---
diff --git a/tools/Makefile.am b/tools/Makefile.am
index 5ee31df0d..26a3bd3d4 100644
--- a/tools/Makefile.am
+++ b/tools/Makefile.am
@@ -38,9 +38,9 @@ noinst_PROGRAMS = introspect operation_reference detect_opencl gegl-tester opera
 gegl_tester_SOURCES = \
        gegl-tester.c
 
-if HAVE_EXIV2
+if HAVE_GEXIV2
 noinst_PROGRAMS     += exp_combine 
 exp_combine_SOURCES  = exp_combine.cpp
-exp_combine_LDADD    = $(EXIV2_LIBS) 
-exp_combine_CXXFLAGS = $(AM_CFLAGS) $(EXIV2_CFLAGS)
+exp_combine_LDADD    = $(GEXIV2_LIBS) 
+exp_combine_CXXFLAGS = $(AM_CFLAGS) $(GEXIV2_CFLAGS)
 endif
diff --git a/tools/exp_combine.cpp b/tools/exp_combine.cpp
index 6b772d35a..c74f81cf6 100644
--- a/tools/exp_combine.cpp
+++ b/tools/exp_combine.cpp
@@ -8,8 +8,7 @@
 
 #include <iostream>
 
-#include <exiv2/image.hpp>
-#include <exiv2/exif.hpp>
+#include <gexiv2/gexiv2.h>
 
 using namespace std;
 
@@ -54,35 +53,32 @@ die:
 static gfloat
 expcombine_get_file_ev (const gchar *path)
 {
-  /* Open the file and read in the metadata */
-  Exiv2::Image::AutoPtr image;
-  try 
-    {
-      image = Exiv2::ImageFactory::open (path);
-      image->readMetadata ();
-    }
-  catch (Exiv2::Error ex)
-    {
-      g_print ("Error: unable to read metadata from path: '%s'\n", path);
-      exit (EXIT_FAILURE);
-    }
+  GError *error = NULL;
+  GExiv2Metadata *e2m = gexiv2_metadata_new ();
+  gfloat time, aperture, gain = 1.0f;
 
-  Exiv2::ExifData &exifData = image->exifData ();
-  if (exifData.empty ())
-      return NAN;
+  gexiv2_metadata_open_path (e2m, path, &error);
+  if (error)
+  {
+    g_warning ("%s", error->message);
+    exit (EXIT_FAILURE);
+  }
 
   /* Calculate the APEX brightness / EV */
-  gfloat time, aperture, gain = 1.0f;
 
-  time     = exifData["Exif.Photo.ExposureTime"].value().toFloat();
-  aperture = exifData["Exif.Photo.FNumber"     ].value().toFloat();
+  {
+    gint nom, den;
+    gexiv2_metadata_get_exposure_time (e2m, &nom, &den);
+    time = nom * 1.0f / den;
+  }
+  aperture = gexiv2_metadata_get_fnumber (e2m);
 
   /* iso */
-  try
+  if (gexiv2_metadata_has_tag (e2m, "Exif.Image.ISOSpeedRatings"))
     {
-      gain = exifData["Exif.Photo.ISOSpeedRatings"].value().toLong() / 100.0f;
+      gain = gexiv2_metadata_get_iso_speed (e2m) / 100.0f;
     }
-  catch (Exiv2::Error ex)
+  else
     {
       // Assume ISO is set at 100. It's reasonably likely that the ISO is the
       // same across all images anyway, and for our purposes the relative