diff --git a/rtgui/batchqueue.cc b/rtgui/batchqueue.cc
index 9fcaa28d1..acb45c266 100644
--- a/rtgui/batchqueue.cc
+++ b/rtgui/batchqueue.cc
@@ -28,6 +28,7 @@
 #include <sstream>
 #include <string>
 
+#include "cachemanager.h"
 #include "thumbnail.h"
 #include "batchqueue.h"
 #include "multilangmgr.h"
diff --git a/rtgui/bqentryupdater.cc b/rtgui/bqentryupdater.cc
index 21a0f5ad0..8f5687b81 100644
--- a/rtgui/bqentryupdater.cc
+++ b/rtgui/bqentryupdater.cc
@@ -17,8 +17,24 @@
  *  along with RawTherapee.  If not, see <https://www.gnu.org/licenses/>.
  */
 #include "bqentryupdater.h"
-#include <gtkmm.h>
+
 #include "guiutils.h"
+#include "../rtengine/utils.h"
+
+namespace
+{
+
+void thumbInterp(const unsigned char* src, int sw, int sh, unsigned char* dst, int dw, int dh)
+{
+
+    if (options.thumbInterp == 0) {
+        rtengine::nearestInterp (src, sw, sh, dst, dw, dh);
+    } else if (options.thumbInterp == 1) {
+        rtengine::bilinearInterp (src, sw, sh, dst, dw, dh);
+    }
+}
+
+}
 
 BatchQueueEntryUpdater batchQueueEntryUpdater;
 
@@ -27,7 +43,7 @@ BatchQueueEntryUpdater::BatchQueueEntryUpdater ()
 {
 }
 
-void BatchQueueEntryUpdater::process (guint8* oimg, int ow, int oh, int newh, BQEntryUpdateListener* listener, rtengine::ProcParams* pparams, Thumbnail* thumbnail)
+void BatchQueueEntryUpdater::process (guint8* oimg, int ow, int oh, int newh, BQEntryUpdateListener* listener, rtengine::procparams::ProcParams* pparams, Thumbnail* thumbnail)
 {
     if (!oimg && (!pparams || !thumbnail)) {
         //printf("WARNING! !oimg && (!pparams || !thumbnail)\n");
diff --git a/rtgui/bqentryupdater.h b/rtgui/bqentryupdater.h
index 1e71c0fc0..4cbbf6e59 100644
--- a/rtgui/bqentryupdater.h
+++ b/rtgui/bqentryupdater.h
@@ -48,7 +48,7 @@ class BatchQueueEntryUpdater
         guint8* oimg;
         int ow, oh, newh;
         BQEntryUpdateListener* listener;
-        rtengine::ProcParams* pparams;
+        rtengine::procparams::ProcParams* pparams;
         Thumbnail* thumbnail;
     };
 
@@ -62,7 +62,7 @@ protected:
 public:
     BatchQueueEntryUpdater ();
 
-    void process    (guint8* oimg, int ow, int oh, int newh, BQEntryUpdateListener* listener, rtengine::ProcParams* pparams = nullptr, Thumbnail* thumbnail = nullptr);
+    void process    (guint8* oimg, int ow, int oh, int newh, BQEntryUpdateListener* listener, rtengine::procparams::ProcParams* pparams = nullptr, Thumbnail* thumbnail = nullptr);
     void removeJobs (BQEntryUpdateListener* listener);
     void terminate  ();
 
diff --git a/rtgui/guiutils.cc b/rtgui/guiutils.cc
index 189cf6178..d6ede26da 100644
--- a/rtgui/guiutils.cc
+++ b/rtgui/guiutils.cc
@@ -217,16 +217,6 @@ bool removeIfThere (Gtk::Container* cont, Gtk::Widget* w, bool increference)
     }
 }
 
-void thumbInterp (const unsigned char* src, int sw, int sh, unsigned char* dst, int dw, int dh)
-{
-
-    if (options.thumbInterp == 0) {
-        rtengine::nearestInterp (src, sw, sh, dst, dw, dh);
-    } else if (options.thumbInterp == 1) {
-        rtengine::bilinearInterp (src, sw, sh, dst, dw, dh);
-    }
-}
-
 bool confirmOverwrite (Gtk::Window& parent, const std::string& filename)
 {
     bool safe = true;
diff --git a/rtgui/guiutils.h b/rtgui/guiutils.h
index 8764f4c6a..97c72513b 100644
--- a/rtgui/guiutils.h
+++ b/rtgui/guiutils.h
@@ -48,7 +48,6 @@ class RTImage;
 
 Glib::ustring escapeHtmlChars(const Glib::ustring &src);
 bool removeIfThere (Gtk::Container* cont, Gtk::Widget* w, bool increference = true);
-void thumbInterp (const unsigned char* src, int sw, int sh, unsigned char* dst, int dw, int dh);
 bool confirmOverwrite (Gtk::Window& parent, const std::string& filename);
 void writeFailed (Gtk::Window& parent, const std::string& filename);
 void drawCrop (Cairo::RefPtr<Cairo::Context> cr, int imx, int imy, int imw, int imh, int startx, int starty, double scale, const rtengine::procparams::CropParams& cparams, bool drawGuide = true, bool useBgColor = true, bool fullImageVisible = true);
diff --git a/rtgui/main.cc b/rtgui/main.cc
index 58fdd12dc..1bb840e1e 100644
--- a/rtgui/main.cc
+++ b/rtgui/main.cc
@@ -33,6 +33,7 @@
 #include <cstdlib>
 #include <locale.h>
 #include <lensfun.h>
+#include "cachemanager.h"
 #include "options.h"
 #include "soundman.h"
 #include "rtimage.h"
diff --git a/rtgui/previewloader.cc b/rtgui/previewloader.cc
index 67de50113..a808e1f71 100644
--- a/rtgui/previewloader.cc
+++ b/rtgui/previewloader.cc
@@ -18,6 +18,8 @@
  */
 
 #include <set>
+#include "cachemanager.h"
+#include "filebrowserentry.h"
 #include "previewloader.h"
 #include "guiutils.h"
 #include "threadutils.h"
diff --git a/rtgui/previewloader.h b/rtgui/previewloader.h
index 3712dc3ff..9a74ee2eb 100644
--- a/rtgui/previewloader.h
+++ b/rtgui/previewloader.h
@@ -22,10 +22,10 @@
 
 #include <glibmm/ustring.h>
 
-#include "filebrowserentry.h"
-
 #include "../rtengine/noncopyable.h"
 
+class FileBrowserEntry;
+
 class PreviewLoaderListener
 {
 public:
diff --git a/rtgui/previewwindow.cc b/rtgui/previewwindow.cc
index 54d785313..c813f04a2 100644
--- a/rtgui/previewwindow.cc
+++ b/rtgui/previewwindow.cc
@@ -88,7 +88,7 @@ void PreviewWindow::updatePreviewImage ()
             cc->fill();
 
             if (previewHandler->getCropParams().enabled) {
-                rtengine::CropParams cparams = previewHandler->getCropParams();
+                rtengine::procparams::CropParams cparams = previewHandler->getCropParams();
                 switch (options.cropGuides) {
                 case Options::CROP_GUIDE_NONE:
                     cparams.guide = "None";
diff --git a/rtgui/rtwindow.cc b/rtgui/rtwindow.cc
index 3654e8af6..45d07c4af 100644
--- a/rtgui/rtwindow.cc
+++ b/rtgui/rtwindow.cc
@@ -19,6 +19,7 @@
 
 #include <gtkmm.h>
 #include "rtwindow.h"
+#include "cachemanager.h"
 #include "preferences.h"
 #include "iccprofilecreator.h"
 #include "cursormanager.h"
diff --git a/rtgui/thumbnail.cc b/rtgui/thumbnail.cc
index 7464244f7..bb911534a 100644
--- a/rtgui/thumbnail.cc
+++ b/rtgui/thumbnail.cc
@@ -15,6 +15,7 @@
  *  You should have received a copy of the GNU General Public License
  *  along with RawTherapee.  If not, see <https://www.gnu.org/licenses/>.
  */
+#include "cachemanager.h"
 #include "multilangmgr.h"
 #include "thumbnail.h"
 #include <sstream>
@@ -25,6 +26,7 @@
 #include "../rtengine/colortemp.h"
 #include "../rtengine/imagedata.h"
 #include "../rtengine/procparams.h"
+#include "../rtengine/rtthumbnail.h"
 #include <glib/gstdio.h>
 
 #include "../rtengine/dynamicprofile.h"
@@ -1151,3 +1153,48 @@ bool Thumbnail::imageLoad(bool loading)
 
     return false;
 }
+
+void Thumbnail::getCamWB(double& temp, double& green) const
+{
+    if (tpp) {
+        tpp->getCamWB  (temp, green);
+    } else {
+        temp = green = -1.0;
+    }
+}
+
+void Thumbnail::getSpotWB(int x, int y, int rect, double& temp, double& green)
+{
+    if (tpp) {
+        tpp->getSpotWB (getProcParams(), x, y, rect, temp, green);
+    } else {
+        temp = green = -1.0;
+    }
+}
+
+void Thumbnail::applyAutoExp (rtengine::procparams::ProcParams& pparams)
+{
+    if (tpp) {
+        tpp->applyAutoExp (pparams);
+    }
+}
+
+const CacheImageData* Thumbnail::getCacheImageData()
+{
+    return &cfs;
+}
+
+std::string Thumbnail::getMD5() const
+{
+    return cfs.md5;
+}
+
+bool Thumbnail::isQuick() const
+{
+    return cfs.thumbImgType == CacheImageData::QUICK_THUMBNAIL;
+}
+
+bool Thumbnail::isPParamsValid() const
+{
+    return pparamsValid;
+}
diff --git a/rtgui/thumbnail.h b/rtgui/thumbnail.h
index 1a0f68409..aee5ee0a6 100644
--- a/rtgui/thumbnail.h
+++ b/rtgui/thumbnail.h
@@ -24,13 +24,21 @@
 #include <glibmm/ustring.h>
 
 #include "cacheimagedata.h"
-#include "cachemanager.h"
 #include "threadutils.h"
 #include "thumbnaillistener.h"
 
-#include "../rtengine/rtengine.h"
-#include "../rtengine/rtthumbnail.h"
+namespace rtengine
+{
+class Thumbnail;
 
+namespace procparams
+{
+
+class ProcParams;
+
+}
+
+}
 class CacheManager;
 
 struct ParamsEdited;
@@ -98,14 +106,8 @@ public:
 
     void              notifylisterners_procParamsChanged(int whoChangedIt);
 
-    bool              isQuick() const
-    {
-        return cfs.thumbImgType == CacheImageData::QUICK_THUMBNAIL;
-    }
-    bool              isPParamsValid() const
-    {
-        return pparamsValid;
-    }
+    bool              isQuick() const;
+    bool              isPParamsValid() const;
     bool              isRecentlySaved () const;
     void              imageDeveloped ();
     void              imageEnqueued ();
@@ -123,29 +125,10 @@ public:
 
     const Glib::ustring&  getExifString () const;
     const Glib::ustring&  getDateTimeString () const;
-    void                  getCamWB  (double& temp, double& green) const
-    {
-        if (tpp) {
-            tpp->getCamWB  (temp, green);
-        } else {
-            temp = green = -1.0;
-        }
-    }
+    void                  getCamWB  (double& temp, double& green) const;
     void                  getAutoWB (double& temp, double& green, double equal, double tempBias);
-    void                  getSpotWB (int x, int y, int rect, double& temp, double& green)
-    {
-        if (tpp) {
-            tpp->getSpotWB (getProcParams(), x, y, rect, temp, green);
-        } else {
-            temp = green = -1.0;
-        }
-    }
-    void                  applyAutoExp (rtengine::procparams::ProcParams& pparams)
-    {
-        if (tpp) {
-            tpp->applyAutoExp (pparams);
-        }
-    }
+    void                  getSpotWB (int x, int y, int rect, double& temp, double& green);
+    void                  applyAutoExp (rtengine::procparams::ProcParams& pparams);
 
     ThFileType      getType ();
     Glib::ustring   getFileName () const
@@ -156,14 +139,8 @@ public:
 
     bool            isSupported ();
 
-    const CacheImageData* getCacheImageData()
-    {
-        return &cfs;
-    }
-    std::string     getMD5   () const
-    {
-        return cfs.md5;
-    }
+    const CacheImageData* getCacheImageData();
+    std::string     getMD5   () const;
 
     int             getRank  () const;
     void            setRank  (int rank);