diff --git a/ImageProcessingShader.cpp b/ImageProcessingShader.cpp
index 11f894f..68a4728 100644
--- a/ImageProcessingShader.cpp
+++ b/ImageProcessingShader.cpp
@@ -15,6 +15,25 @@ ImageProcessingShader::ImageProcessingShader()
     reset();
 }
 
+ImageProcessingShader::ImageProcessingShader(const ImageProcessingShader &S)
+{
+    program_ = &imageProcessingShadingProgram;
+    reset();
+    brightness = S.brightness;
+    contrast = S.contrast;
+    saturation = S.saturation;
+    hueshift = S.hueshift;
+    threshold = S.threshold;
+    lumakey = S.lumakey;
+    nbColors = S.nbColors;
+    invert = S.invert;
+    filterid = S.filterid;
+    gamma = S.gamma;
+    levels = S.levels;
+    chromakey = S.chromakey;
+    chromadelta = S.chromadelta;
+}
+
 void ImageProcessingShader::use()
 {
     Shader::use();
diff --git a/ImageProcessingShader.h b/ImageProcessingShader.h
index c918114..23d77fc 100644
--- a/ImageProcessingShader.h
+++ b/ImageProcessingShader.h
@@ -11,7 +11,7 @@ class ImageProcessingShader : public Shader
 public:
 
     ImageProcessingShader();
-//    virtual ~ImageProcessingShader() {}
+    ImageProcessingShader(const ImageProcessingShader &model);
 
     void use() override;
     void reset() override;
diff --git a/SessionCreator.cpp b/SessionCreator.cpp
index 302ff3c..ff0c002 100644
--- a/SessionCreator.cpp
+++ b/SessionCreator.cpp
@@ -261,7 +261,9 @@ void SessionCreator::visit (Source& s)
     s.blendingShader()->accept(*this);
 
     xmlCurrent_ = sourceNode->FirstChildElement("ImageProcessing");
+    bool on = xmlCurrent_->BoolAttribute("enabled", true);
     s.processingShader()->accept(*this);
+    s.setImageProcessingEnabled(on);
 
     // restore current
     xmlCurrent_ = sourceNode;
diff --git a/SessionVisitor.cpp b/SessionVisitor.cpp
index bc14061..35e1194 100644
--- a/SessionVisitor.cpp
+++ b/SessionVisitor.cpp
@@ -317,6 +317,7 @@ void SessionVisitor::visit (Source& s)
     s.blendingShader()->accept(*this);
 
     xmlCurrent_ = xmlDoc_->NewElement( "ImageProcessing" );
+    xmlCurrent_->SetAttribute("enabled", s.imageProcessingEnabled());
     sourceNode->InsertEndChild(xmlCurrent_);
     s.processingShader()->accept(*this);
 
diff --git a/Source.cpp b/Source.cpp
index 558b3c5..9154b3d 100644
--- a/Source.cpp
+++ b/Source.cpp
@@ -199,20 +199,32 @@ void Source::setMode(Source::Mode m)
 
 void Source::setImageProcessingEnabled (bool on)
 {
+    // avoid repeating
     if ( on == imageProcessingEnabled() )
         return;
 
     // set pointer
     if (on) {
-        processingshader_   = new ImageProcessingShader;
+        // set the current rendering shader to be the
+        // (previously prepared) processing shader
         renderingshader_ = (Shader *) processingshader_;
-
-    } else {
-        processingshader_   = nullptr;
+    }
+    else {
+        // clone the current Image processing shader
+        //  (because the one currently attached to the source
+        //   will be deleted in replaceRenderngShader().)
+        ImageProcessingShader *tmp = new ImageProcessingShader(*processingshader_);
+        // loose reference to current processing shader (to delete)
+        // and keep reference to the newly created one
+        // and keep it for later
+        processingshader_ = tmp;
+        // set the current rendering shader to a simple one
         renderingshader_ = (Shader *) new ImageShader;
     }
 
     // apply to nodes in subclasses
+    // this calls replaceShader() on the Primitive and
+    // will delete the previously attached shader
     replaceRenderingShader();
 }