Copyright (c) 2021 BitBank Software, Inc.
Written by Larry Bank
[email protected]
An 'embedded-friendly' (aka Arduino) JPEG image encoding library
Starting in the late 80's I wrote my own imaging codecs for the existing standards (CCITT G3/G4 was the first). I soon added GIF, JPEG and not long after that, the PNG specification was ratified. All of this code was "clean room" - written just from the specification. I used my imaging library in many projects and products over the years and recently decided that some of my codecs could get a new lease on life as open source, embedded-friendly libraries for microcontrollers.
There are many open source libraries written for Linux that would be useful to run on embedded processors. What stops them from "just working" is that they depend on a file system, heap management and sometimes additional external dependencies. The purpose of this project is to provide a fast and convenient JPEG encoder which can run without an operating system or even a C-Runtime library. I've optimized the code for speed and memory usage so it should be faster than any other FOSS libraries available.
Feature summary:
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- Runs on any MCU with at least 4K of free RAM
- No external dependencies (including malloc/free)
- Encode an image MCU by MCU
- Encode directly to your own buffer or a file with I/O callbacks you provide
- Supported pixel types: grayscale, RGB565, RGB888 and ARGB8888 (alpha ignored)
- Allows for optional color subsampling (4:4:4 or 4:2:0)
- Supports 4 quality levels (LOW, MED, HIGH, BEST)
- Arduino-style C++ library class with simple API
- Can by built as straight C as well
How fast is it?
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The examples folder contains a sketch to measure the performance of encoding a 1024x1024 image generated dynamically.
Documentation:
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Detailed information about the API is in the Wiki
See the examples folder for easy starting points