From c2199009807f3aa1f646e7e2c7472233857b3a2f Mon Sep 17 00:00:00 2001
From: Davis King <davis@dlib.net>
Date: Sun, 25 Oct 2015 18:13:22 -0400
Subject: [PATCH] Added image_plane()

---
 dlib/dnn/tensor.h          | 25 +++++++++++++++++++++++++
 dlib/dnn/tensor_abstract.h | 20 ++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/dlib/dnn/tensor.h b/dlib/dnn/tensor.h
index bf015d43c..d8be005d2 100644
--- a/dlib/dnn/tensor.h
+++ b/dlib/dnn/tensor.h
@@ -241,6 +241,31 @@ namespace dlib
         return mat(t, t.num_samples(), t.size()/t.num_samples());
     }
 
+    inline const matrix_op<op_pointer_to_mat<float> > image_plane (
+        const tensor& t,
+        long sample = 0,
+        long k = 0
+    )
+    {
+        DLIB_ASSERT(0 <= sample && sample < t.num_samples() &&
+                    0 <= k && k < t.k() &&
+                    t.size() != 0, 
+                    "\tconst matrix_exp image_plane(tensor,sample,k)"
+                    << "\n\t Invalid arguments were given to this function."
+                    << "\n\t sample: " << sample
+                    << "\n\t k:      " << k 
+                    << "\n\t t.num_samples(): " << t.num_samples() 
+                    << "\n\t t.k():           " << t.k() 
+                    << "\n\t t.size():        " << t.size() 
+        );
+
+
+        typedef op_pointer_to_mat<float> op;
+        return matrix_op<op>(op(t.host() + ((sample*t.k() + k)*t.nr())*t.nc(), 
+                                t.nr(), 
+                                t.nc()));
+    }
+
 // ----------------------------------------------------------------------------------------
 
     inline bool have_same_dimensions (
diff --git a/dlib/dnn/tensor_abstract.h b/dlib/dnn/tensor_abstract.h
index 2bc8c6c5d..9a1169765 100644
--- a/dlib/dnn/tensor_abstract.h
+++ b/dlib/dnn/tensor_abstract.h
@@ -295,6 +295,26 @@ namespace dlib
             - returns mat(t, t.num_samples(), t.size()/t.num_samples())
     !*/
 
+    const matrix_exp image_plane (
+        const tensor& t,
+        long sample = 0,
+        long k = 0
+    );
+    /*!
+        requires
+            - t.size() != 0
+            - 0 <= sample < t.num_samples()
+            - 0 <= k < t.k()
+        ensures
+            - returns the k-th image plane from the sample-th image in t.  That is,
+              returns a matrix M such that:
+                - M contains float valued elements.
+                - M.nr() == t.nr()
+                - M.nc() == t.nc()
+                - for all valid r and c:
+                    - M(r,c) == t.host()[((sample*t.k() + k)*t.nr() + r)*t.nc() + c]
+    !*/
+
 // ----------------------------------------------------------------------------------------
 
     bool have_same_dimensions (