Made image saving routines work on matrix objects in addition to array2d

objects.

dlib/image_saver/image_saver.h

@@ -17,6 +17,8 @@
 #include "../dir_nav.h"
 #include "../float_details.h"
 #include "../vectorstream.h"
+#include "../matrix/matrix_exp.h"
+#include "../image_transforms/assign_image.h"
 
 namespace dlib
 {
@@ -229,7 +231,7 @@ namespace dlib
     template <
         typename image_type 
         >
-    inline void save_bmp (
+    inline typename disable_if<is_matrix<image_type> >::type save_bmp (
         const image_type& image,
         std::ostream& out
     )
@@ -237,6 +239,19 @@ namespace dlib
         save_bmp_helper<image_type>::save_bmp(image,out);
     }
 
+    template <
+        typename EXP 
+        >
+    inline void save_bmp (
+        const matrix_exp<EXP>& image,
+        std::ostream& out
+    )
+    {
+        array2d<typename EXP::type> temp;
+        assign_image(temp, image);
+        save_bmp_helper<array2d<typename EXP::type> >::save_bmp(temp,out);
+    }
+
 // ----------------------------------------------------------------------------------------
 
     namespace dng_helpers_namespace
@@ -578,7 +593,7 @@ namespace dlib
     template <
         typename image_type 
         >
-    inline void save_dng (
+    inline typename disable_if<is_matrix<image_type> >::type save_dng (
         const image_type& image,
         std::ostream& out
     )
@@ -587,6 +602,20 @@ namespace dlib
         save_dng_helper<image_type>::save_dng(image,out);
     }
 
+    template <
+        typename EXP 
+        >
+    inline void save_dng (
+        const matrix_exp<EXP>& image,
+        std::ostream& out
+    )
+    {
+        array2d<typename EXP::type> temp;
+        assign_image(temp, image);
+        using namespace dng_helpers_namespace;
+        save_dng_helper<array2d<typename EXP::type> >::save_dng(temp,out);
+    }
+
 // ----------------------------------------------------------------------------------------
 
     template <typename image_type>

dlib/image_saver/image_saver_abstract.h

@@ -29,7 +29,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
+            - image_type == is an implementation of array2d/array2d_kernel_abstract.h or
+              a dlib::matrix
             - pixel_traits<typename image_type::type> is defined  
         ensures
             - writes the image to the out stream in the Microsoft Windows BMP format.
@@ -57,7 +58,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
+            - image_type == is an implementation of array2d/array2d_kernel_abstract.h or
+              a dlib::matrix
             - pixel_traits<typename image_type::type> is defined  
         ensures
             - opens the file indicated by file_name with an output file stream named fout
@@ -83,7 +85,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
+            - image_type == is an implementation of array2d/array2d_kernel_abstract.h or
+              a dlib::matrix
             - pixel_traits<typename image_type::type> is defined  
         ensures
             - writes the image to the out stream in the dlib dng format.
@@ -111,7 +114,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
+            - image_type == is an implementation of array2d/array2d_kernel_abstract.h or
+              a dlib::matrix
             - pixel_traits<typename image_type::type> is defined  
         ensures
             - opens the file indicated by file_name with an output file stream named fout 

dlib/image_saver/save_png.h

@@ -9,6 +9,8 @@
 #include <vector>
 #include <string>
 #include "../pixel.h"
+#include "../matrix/matrix_exp.h"
+#include "../image_transforms/assign_image.h"
 
 namespace dlib
 {
@@ -38,7 +40,7 @@ namespace dlib
     template <
         typename image_type
         >
-    void save_png(
+    typename disable_if<is_matrix<image_type> >::type save_png(
         const image_type& img,
         const std::string& file_name
     )
@@ -130,6 +132,24 @@ namespace dlib
 #endif
 
     }
+
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename EXP 
+        >
+    void save_png(
+        const matrix_exp<EXP>& img,
+        const std::string& file_name
+    )
+    {
+        array2d<typename EXP::type> temp;
+        assign_image(temp, img);
+        save_png(temp, file_name);
+    }
+
+// ----------------------------------------------------------------------------------------
+
 }
 
 #ifdef NO_MAKEFILE

dlib/image_saver/save_png_abstract.h

@@ -19,7 +19,8 @@ namespace dlib
     );
     /*!
         requires
-            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
+            - image_type == is an implementation of array2d/array2d_kernel_abstract.h or
+              a dlib::matrix
             - pixel_traits<typename image_type::type> is defined  
             - image.size() != 0
         ensures