libheif

README

libheif

libheif is an ISO/IEC 23008-12:2017 HEIF and AVIF (AV1 Image File Format) file format decoder and encoder.

HEIF and AVIF are new image file formats employing HEVC (h.265) or AV1 image coding, respectively, for the best compression ratios currently possible.

libheif makes use of libde265 for HEIF image decoding and x265 for encoding. For AVIF, libaom is used as encoder and decoder. Alternative codecs for, e.g., AVC and JPEG can be provided as plugins.

Supported features

libheif has support for decoding

• tiled images
• alpha channels (currently HEIF only)
• thumbnails
• reading EXIF and XMP metadata
• reading the depth channel
• multiple images in a file
• image transformations (crop, mirror, rotate)
• overlay images
• plugin interface to add alternative codecs for additional formats (AVC, JPEG)
• decoding of files while downloading (e.g. extract image size before file has been completely downloaded)
• reading color profiles
• heix images (10 and 12 bit, chroma 4:2:2)

The encoder supports:

• lossy compression with adjustable quality
• lossless compression
• alpha channels (currently HEIF only)
• thumbnails
• save multiple images to a file
• save EXIF and XMP metadata
• writing color profiles
• 10 and 12 bit images (currently HEIF only)
• monochrome images (currently HEIF only)

API

The library has a C API for easy integration and wide language support. Note that the API is still work in progress and may still change.

The decoder automatically supports both HEIF and AVIF through the same API. No changes are required to existing code to support AVIF. The encoder can be switched between HEIF and AVIF simply by setting heif_compression_HEVC or heif_compression_AV1 to heif_context_get_encoder_for_format().

Loading the primary image in an HEIF file is as easy as this:

heif_context* ctx = heif_context_alloc();
heif_context_read_from_file(ctx, input_filename, nullptr);

// get a handle to the primary image
heif_image_handle* handle;
heif_context_get_primary_image_handle(ctx, &handle);

// decode the image and convert colorspace to RGB, saved as 24bit interleaved
heif_image* img;
heif_decode_image(handle, &img, heif_colorspace_RGB, heif_chroma_interleaved_RGB, nullptr);

int stride;
const uint8_t* data = heif_image_get_plane_readonly(img, heif_channel_interleaved, &stride);

Writing an HEIF file can be done like this:

heif_context* ctx = heif_context_alloc();

// get the default encoder
heif_encoder* encoder;
heif_context_get_encoder_for_format(ctx, heif_compression_HEVC, &encoder);

// set the encoder parameters
heif_encoder_set_lossy_quality(encoder, 50);

// encode the image
heif_image* image; // code to fill in the image omitted in this example
heif_context_encode_image(ctx, nullptr, image, encoder);

heif_encoder_release(encoder);

heif_context_write_to_file(context, "output.heic");

See the header file heif.h for the complete C API.

There is also a C++ API which is a header-only wrapper to the C API. Hence, you can use the C++ API and still be binary compatible. Code using the C++ API is much less verbose than using the C API directly.

There is also an experimental Go API, but this is not stable yet.

Compiling

This library uses a standard autoconf/automake build system. After downloading, run ./autogen.sh to build the configuration scripts, then call ./configure and make. Make sure that you compile and install libde265 first, so that the configuration script will find this. Preferably, download the frame-parallel branch of libde265, as this uses a more recent API than version in the master branch. Also install x265 and its development files if you want to use HEIF encoding.

For AVIF support, make sure that libaom is installed.

macOS

1. Install dependencies with Homebrew

   brew install automake make pkg-config x265 libde265 libjpeg
   

2. Configure and build project

   ./autogen.sh
   ./configure
   make
   

Compiling to JavaScript

libheif can also be compiled to JavaScript using emscripten. See the build-emscripten.sh for further information.

Online demo

Check out this online demo. This is libheif running in JavaScript in your browser.

Example programs

Some example programs are provided in the examples directory. The program heif-convert converts all images stored in an HEIF/AVIF file to JPEG or PNG. heif-enc lets you convert JPEG files to HEIF/AVIF. The program heif-info is a simple, minimal decoder that dumps the file structure to the console.

For example convert example.heic to JPEGs and one of the JPEGs back to HEIF:

cd examples/
./heif-convert example.heic example.jpeg
./heif-enc example-1.jpeg -o example.heif

In order to convert example-1.jpeg to AVIF use:

./heif-enc example-1.jpeg -A -o example.avif

There is also a GIMP plugin using libheif here.

HEIF/AVIF thumbnails for the Gnome desktop

The program heif-thumbnailer can be used as an HEIF/AVIF thumbnailer for the Gnome desktop. The matching Gnome configuration files are in the gnome directory. Place the file heif.xml into /usr/share/mime/packages and heif.thumbnailer into /usr/share/thumbnailers. You may have to run update-mime-database /usr/share/mime to update the list of known MIME types.

License

The libheif is distributed under the terms of the GNU Lesser General Public License. The sample applications are distributed under the terms of the MIT License.

See COPYING for more details.

Copyright (c) 2017-2020 Struktur AG Contact: Dirk Farin farin@struktur.de