# 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``, or insert the **SD memory card** into the development board ``SD card``
- 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 [Button](lab_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.