jpec - a JPEG encoder in C

Overview

jpec is a minimalistic JPEG encoder written in C with a focus on simplicity.

It is both portable (tested on x86 and ARM) and lightweight (around 600 LOC).

The library has no external dependencies.

It is a perfect candidate if you have some embedded C code you need to extend with a JPEG encoder the easy way, e.g. it is currently used in production within the Moodstocks SDK (as of release v3.1) to compress frames that are sent to Moodstocks API search service.

If you want to know more, feel free to read this blog post.

Features

The library allows you to write JPEG compressed images from input image data on memory. No more, no less.

More precisely:

• it works in grayscale only (monochrome JPEG file): there is no support for color so far,
• it produces baseline, DCT-based (SOF0), JFIF 1.01 (APP0) JPEG-s,
• it supports 8x8 blocks only,
• it includes default quantization and Huffman tables that are not customizable at runtime.

Build

Just type:

make

This produces:

• libjpec.a: the static library,
• jpec: a simple command-line tool used to test the library (see main.c)

NOTE the command-line tool depends on OpenCV HighGUI module to easily read any kind of input image. You need to have OpenCV development libraries installed on your machine to use it (e.g. brew install opencv on Mac OS X with Homebrew).

Usage

If you want to embed the library into your own C code you are free to create the static library file, and include jpec.h main header, or to copy-paste the whole code into your project.

Then, encoding a raw image is a matter of a few lines of code:

    /* Create a JPEG encoder provided image data */
    jpec_enc_t *e = jpec_enc_new(img, w, h);

    /* Compress */
    int len;
    const uint8_t *jpeg = jpec_enc_run(e, &len);

    /* Do something with the JPEG blob (e.g. save into a file, etc) */

    /* Release the encoder */
    jpec_enc_del(e);

Authors

Maxime Brénon & Cédric Deltheil.

Copyright

Copyright (c) 2012 Moodstocks SAS