18.5. PNG encode

18.5.1. Overview

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

18.5.2. 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

    UDisk_Format

  • Connect LCD screen and Cam camera to development board

18.5.3. 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

18.5.4. Store picture size

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

18.5.5. 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 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.