Further reduction of include dependencies

rtengine/iimage.cc

@@ -17,6 +17,7 @@
  *  along with RawTherapee.  If not, see <https://www.gnu.org/licenses/>.
  */
 
+#include "color.h"
 #include "procparams.h"
 #include "rtengine.h"
 
@@ -45,3 +46,6 @@ int rtengine::getCoarseBitMask( const procparams::CoarseTransformParams &coarse)
 
     return tr;
 }
+int rtengine::igammasrgb(float in) {
+    return Color::igamma_srgb(in);
+}