.. _png_encode:

PNG encode
====================

Overview
--------

PNG decoding example project demonstrates how to encode an image capture from camera sensor to a PNG file using LodePNG library

Board Setting
-------------

- Connect the **USB disk**  to the development board ``usb0`` (Attention: The `Cluster Size` of the USB disk can't exceed 32KB, it is recommended that the format parameter is FAT32/32KB), or insert the **SD memory card**  into the development board ``SD card``

  .. image:: ../../../../../samples/image/common/doc/UDisk_Format.png
     :alt: UDisk_Format

- Connect **LCD screen**  and **Cam camera**  to development board

Engineering configuration
-------------------------

- File `CMakeLists.txt`:

- If `set (PNG_USE_SDCARD 1)` is configured, png files are stored in SD card or ``set (PNG_USE_UDISK 1)`` , they will be saved to udisk.

- if use ov7725 camera device, configure `set(CONFIG_CAMERA "ov7725")` in CMakeList.txt

- if use ov5640 camera device, configure `set(CONFIG_CAMERA "ov5640")` in CMakeList.txt

Store picture size
------------------

- The image format stored in this routine is PNG, and the resolution size is 640*480

Running the example
-------------------

- Configure storage in CMakeLists.txt，default is PNG_USE_SDCARD.

- Connect camera senor, LCD pannel and storage to board

- Power on the board

- Download built elf into development board and run the demo

- If everything goes well:

  - camera sensor preview will be shown on LCD panel

  - press GPIO button (please check  :ref:`Button <board_resource>`  section of specific board) will save current frame and encode to png file and save to target storage

  - encoded image will be decoded and shown on LCD pannel until GPIO button is pressed again. Once it's been pressed, preview will be resumed.