New structure (following the documentation) for the tutorials. Normalized image sizes for TOC display.

doc/tutorials/core/adding_images/adding_images.rst

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+.. _Adding_Images:
+
+Adding (blending) two images using OpenCV
+*******************************************
+
+Goal
+=====
+
+In this tutorial you will learn how to:
+
+* What is *linear blending* and why it is useful.
+* Add two images using :add_weighted:`addWeighted <>`
+
+Cool Theory
+=================
+
+.. note::
+
+   The explanation below belongs to the book `Computer Vision: Algorithms and Applications <http://szeliski.org/Book/>`_  by Richard Szeliski 
+
+From our previous tutorial, we know already a bit of *Pixel operators*. An interesting dyadic (two-input) operator is the *linear blend operator*:
+
+.. math::
+
+   g(x) = (1 - \alpha)f_{0}(x) + \alpha f_{1}(x)
+
+By varying :math:`\alpha` from :math:`0 \rightarrow 1` this operator can be used to perform a temporal *cross-disolve* between two images or videos, as seen in slide shows and film production (cool, eh?)
+
+Code
+=====
+
+As usual, after the not-so-lengthy explanation, let's go to the code. Here it is:
+
+.. code-block:: cpp
+
+   #include <cv.h>
+   #include <highgui.h>
+   #include <iostream>
+
+   using namespace cv;
+
+   int main( int argc, char** argv )
+   {
+    double alpha = 0.5; double beta; double input; 
+
+    Mat src1, src2, dst;
+
+    /// Ask the user enter alpha
+    std::cout<<" Simple Linear Blender "<<std::endl;
+    std::cout<<"-----------------------"<<std::endl;
+    std::cout<<"* Enter alpha [0-1]: ";
+    std::cin>>input;
+
+    /// We use the alpha provided by the user iff it is between 0 and 1
+    if( alpha >= 0 && alpha <= 1 )
+      { alpha = input; }
+
+    /// Read image ( same size, same type )
+    src1 = imread("../../images/LinuxLogo.jpg");
+    src2 = imread("../../images/WindowsLogo.jpg");
+
+    if( !src1.data ) { printf("Error loading src1 \n"); return -1; }
+    if( !src2.data ) { printf("Error loading src2 \n"); return -1; }
+
+    /// Create Windows
+    namedWindow("Linear Blend", 1);
+
+    beta = ( 1.0 - alpha );
+    addWeighted( src1, alpha, src2, beta, 0.0, dst);
+  
+    imshow( "Linear Blend", dst );
+
+    waitKey(0);
+    return 0;
+   }
+
+Explanation
+============
+
+#. Since we are going to perform:
+
+   .. math::
+
+      g(x) = (1 - \alpha)f_{0}(x) + \alpha f_{1}(x)
+
+   We need two source images (:math:`f_{0}(x)` and :math:`f_{1}(x)`). So, we load them in the usual way:
+
+   .. code-block:: cpp
+
+      src1 = imread("../../images/LinuxLogo.jpg");
+      src2 = imread("../../images/WindowsLogo.jpg");
+
+   .. warning::
+
+      Since we are *adding* *src1* and *src2*, they both have to be of the same size (width and height) and type.
+
+#. Now we need to generate the :math:`g(x)` image. For this, the function :add_weighted:`addWeighted <>` comes quite handy:
+
+   .. code-block:: cpp
+   
+      beta = ( 1.0 - alpha );
+      addWeighted( src1, alpha, src2, beta, 0.0, dst);
+ 
+   since :add_weighted:`addWeighted <>` produces:
+
+   .. math::
+
+      dst = \alpha \cdot src1 + \beta \cdot src2 + \gamma
+
+   In this case, :math:`\gamma` is the argument :math:`0.0` in the code above.
+ 
+#. Create windows, show the images and wait for the user to end the program. 
+
+Result
+=======
+
+.. image:: images/Adding_Images_Tutorial_Result_0.png
+   :alt: Blending Images Tutorial - Final Result
+   :align: center