diff --git a/dlib/opencv/cv_image.h b/dlib/opencv/cv_image.h
index 05af05511..31b96751c 100644
--- a/dlib/opencv/cv_image.h
+++ b/dlib/opencv/cv_image.h
@@ -23,7 +23,7 @@ namespace dlib
         typedef pixel_type type;
         typedef default_memory_manager mem_manager_type;
 
-        cv_image (const cv::Mat img) 
+        cv_image (const cv::Mat &img) 
         {
             DLIB_CASSERT(img.depth() == cv::DataType<typename pixel_traits<pixel_type>::basic_pixel_type>::depth &&
                          img.channels() == pixel_traits<pixel_type>::num, 
@@ -119,34 +119,6 @@ namespace dlib
         long nc() const { return _nc; }
         long width_step() const { return _widthStep; }
 
-        cv_image& operator=( const cv_image& item)
-        {
-            _data = item._data;
-            _widthStep = item._widthStep;
-            _nr = item._nr;
-            _nc = item._nc;
-            return *this;
-        }
-
-        cv_image& operator=( const IplImage* img)
-        {
-            init(img);
-            return *this;
-        }
-
-        cv_image& operator=( const IplImage img)
-        {
-            init(&img);
-            return *this;
-        }
-
-        cv_image& operator=( const cv::Mat img)
-        {
-            IplImage temp = img;
-            init(&temp);
-            return *this;
-        }
-
     private:
 
         void init (const IplImage* img) 
diff --git a/dlib/opencv/cv_image_abstract.h b/dlib/opencv/cv_image_abstract.h
index 6fbc56b43..d019d148d 100644
--- a/dlib/opencv/cv_image_abstract.h
+++ b/dlib/opencv/cv_image_abstract.h
@@ -181,70 +181,6 @@ namespace dlib
                   of this image
         !*/
 
-        cv_image& operator= ( 
-            const cv_image& item
-        );
-        /*!
-            ensures
-                - #*this is an identical copy of item
-                - returns #*this
-        !*/
-
-        cv_image& operator=( 
-            const IplImage* img
-        );
-        /*!
-            requires
-                - img->dataOrder == 0
-                  (i.e. Only interleaved color channels are supported with cv_image)
-                - (img->depth&0xFF)/8*img->nChannels == sizeof(pixel_type)
-                  (i.e. The size of the pixel_type needs to match the size of the pixels 
-                  inside the OpenCV image)
-            ensures
-                - #nr() == img->height
-                  #nc() == img->width
-                - using the operator[] on this object you will be able to access the pixels
-                  inside this OpenCV image.
-                - returns #*this
-        !*/
-
-        cv_image& operator=( 
-            const IplImage img
-        );
-        /*!
-            requires
-                - img->dataOrder == 0
-                  (i.e. Only interleaved color channels are supported with cv_image)
-                - (img->depth&0xFF)/8*img->nChannels == sizeof(pixel_type)
-                  (i.e. The size of the pixel_type needs to match the size of the pixels 
-                  inside the OpenCV image)
-            ensures
-                - #nr() == img->height
-                  #nc() == img->width
-                - using the operator[] on this object you will be able to access the pixels
-                  inside this OpenCV image.
-                - returns #*this
-        !*/
-
-        cv_image& operator=( 
-            const cv::Mat img
-        );
-        /*!
-            requires
-                - img.depth() == cv::DataType<pixel_traits<pixel_type>::basic_pixel_type>::depth
-                  (i.e. The pixel_type template argument needs to match the type of pixel 
-                  used inside the OpenCV image)
-                - img.channels() == pixel_traits<pixel_type>::num
-                  (i.e. the number of channels in the pixel_type needs to match the number of 
-                  channels in the OpenCV image)
-            ensures
-                - #nr() == img.rows
-                - #nc() == img.cols
-                - using the operator[] on this object you will be able to access the pixels
-                  inside this OpenCV image.
-                - returns #*this
-        !*/
-
         long width_step (
         ) const;
         /*!