trying to convert README to rst

esp32/README.rst

@@ -32,7 +32,9 @@ Installing esp-idf toolchain
 ============================
 
 First thing to do is to install the toolchain for the esp32 (see https://docs.espressif.com/projects/esp-idf/en/latest/get-started/index.html)
+
 .. code:: shell
+
   ### install some dependencies ###
   sudo apt-get install -y git wget libncurses-dev flex bison gperf python python-pip python-setuptools python-serial python-click python-cryptography python-future python-pyparsing python-pyelftools ninja-build ccache libffi-dev libssl-dev
 
@@ -67,3 +69,112 @@ Fast way:
 
 The second way is by using the script in esp32/scripts/build_opencv_for_esp32.sh. This script automatically compiles OpenCV from this repository sources, and install the needed files into the desired project. It can tweaked as needed to add and remove some parts. 
 
+The script has 2 arguments. The first is the path to the  `toolchain-esp32.cmake` (default is `$HOME/esp/esp-idf/tools/cmake/toolchain-esp32.cmake`), and the second is the path where the OpenCV library is installed (default is in esp32/lib).
+
+
+
+Detailed way:
+-------------
+
+The last way explains all the commands and modifications done to be able to compile and run OpenCV on the ESP32. The detailed procedure is in esp32/doc/detailed_build_procedure.md.
+
+
+
+Get project RAM and Flash usages
+===================================
+
+At compilation time:
+--------------------
+
+- The command below can be used to see the different segments sizes of the application :
+
+  .. code shell
+
+    $ xtensa-esp32-elf-size -d -A build/<project-name>.elf
+
+- The file `build/<project-name>.map` is also very useful. It indicates the memory mapping of the variables and can be used to find big variables in the application. 
+
+
+
+At run time:
+------------
+
+.. code:: c++
+
+  // Get the amount of stack (in Bytes) that remained unused when the task stack was at its greatest value
+  ESP_LOGI(TAG, "task stack watermark: %d Bytes", uxTaskGetStackHighWaterMark(NULL));
+  // Get the free heap in Bytes (may not be contiguous)
+  ESP_LOGI(TAG, "heap left: %d Bytes", esp_get_free_heap_size());
+
+
+Adding images codecs support
+============================
+
+Things done to read/writes images in JPEG, PNG, etc..
+
+PNG
+"""
+
+- Remove `-DWITH_PNG=OFF` and add `-DBUILD_PNG=ON` and `-DBUILD_ZLIB=ON` of the cmake command
+  - => The lib `opencv_imgcodecs.a` build pass
+
+The library is compiled in the `3rdparty/` folder. Copy this folder into the esp32 example project folder.
+
+
+
+JPEG
+""""
+
+- Remove `-DWITH_JPEG=OFF` and add `-DBUILD_JPEG=ON` of the cmake command
+  - => Problem at compilation time. TODO
+
+
+
+Adding parallel support
+=======================
+
+TODO
+
+
+
+Removing OpenCV unnecessary parts 
+=================================
+
+Opencv is quite big, even when compiling only the core, imgproc and imgcodec modules. Because the ESP32 has limited resources, it is a good idea to remove some parts of opencv that are in most cases not used. 
+
+
+
+TODO: List the modules functionalities and what is kept or not
+
+Core module:
+------------
+
+
+
+
+Imgproc module:
+---------------
+
+Colorspaces
+"""""""""""
+
+Opencv supports multiple colorspaces (RGB, BGR, RGB565, RGBA, CIELAB, CIEXYZ, Luv, YUV, HSV, HLS, YCrCb, Bayer, Gray). All these colorspaces are not mandatory for an embedded system, so some are removed.
+
+- `color_lab.cpp`: This file contains conversion for CIELAB and CIEXYZ (https://en.wikipedia.org/wiki/CIELAB_color_space). The conversion tables takes a lot of space in the .bss segment (~88kB) , which is already overflowing. Here are the steps done to disable this code:
+  
+  - Move `color_lab.cpp` to `color_lab.cpp.bak` 
+  
+  - In `color.hpp` disable :
+  
+    .. code:: c++
+
+      // todo
+    
+  - In `color.cpp` disable:
+  
+    .. code:: c++
+
+      // todo
+  
+- todo
+