High Efficiency Image File Format


High Efficiency Image File Format is a digital container format for storing individual digital images and image sequences. The standard covers multimedia files that can also include other media streams, such as timed text, audio and video.
HEIF can store images encoded with multiple coding formats, for example both SDR and HDR images. HEVC is an image and video encoding format and the default image codec used with HEIF. HEIF files containing HEVC-encoded images are also known as HEIC files and are mandated to use the .heic filename extension or .heics as stated in the standard. Such files require less storage space than the equivalent quality JPEG.
HEIF files are a special case of the ISO base media file format, first defined in 2001 as a shared part of MP4 and JPEG 2000. Introduced in 2015, it was developed by the Moving Picture Experts Group and is defined as Part 12 within the MPEG-H media suite.

History

The requirements and main use cases of HEIF were defined in 2013.
The technical development of the specification took about one and a half years and was finalized in the middle of 2015.
Apple was the first major adopter of the format in 2017 with the introduction of iOS 11 using the HEIC variant. While HEIC became the default for iPhones, it is possible to revert the settings to allow photos to be recorded in the JPEG format.
Android devices containing the appropriate hardware encoders received support for HEIC files with the release of Android 10.
On some systems, pictures stored in the HEIC format are converted automatically to the older JPEG format when they are sent outside of the system, although incompatibility has led to problems such as US Advanced Placement test takers failing due to their phones uploading unsupported HEIC images by default, leading the College Board to request students change the settings to send only JPEG files.
Although HEIC is gaining in popularity, it is not universally supported; Adobe Photoshop is an example of a popular image editing software that only supports HEIC with color depth of 8-bit but not 10- or 12-bit.
camera hardware is increasingly supporting HEIC file output, with color depth often higher than 8-bit color.

Specifications

HEIF files can store the following types of data:
; Image items: Storage of individual images, image properties and thumbnails.
; Image derivations: Derived images enable non-destructive image editing, and are created on the fly by the rendering software using editing instructions stored separately in the HEIF file. These instructions and images are stored separately in the HEIF file, and describe specific transformations to be applied to the input images. The storage overhead of derived images is small.
; Image sequences:Storage of multiple time-related and/or temporally predicted images, their properties and thumbnails. Different prediction options can be used in order to exploit the temporal and spatial similarities between the images. Hence, file sizes can be drastically reduced when many images are stored in the same HEIF file.
; Auxiliary image items: Storage of image data, such as an alpha plane or a depth map, which complements another image item. These data are not displayed as such, but used in various forms to complement another image item.
; Image metadata: Storage of Exif, XMP and similar metadata which accompany the images stored in the HEIF file.

Encodings inside the container

The HEIF container can store files encoded with various codecs, including:
As users cannot easily tell what encoding and encoding parameters an image was stored in, the HEIF container format can be confusing and makes comparison statements like “HEIF is better than JPEG” vague and inaccurate.
Simply knowing a file is in the HEIF container does not reveal much information, as it could be:
  • a JFIF ;
  • a poor quality AV1; or
  • a very high quality AV1 encoding ; or
  • an HEVC with poor quality parameters; or
  • an HEVC with high quality parameters.

    MIAF

The Multi-Image Application Format is a restricted subset of HEIF specified as part of MPEG-A.
It defines a set of additional constraints to simplify format options, specific alpha plane formats, profiles and levels as well as metadata formats and brands, and rules for how to extend the format.

HEIC: HEVC in HEIF

is an encoding format for graphic data, first standardized in 2013.
It is the primarily used and implied default codec for HEIF as specified in the normative Annex B to ISO/IEC 23008-12 HEVC Image File Format.
While not introduced formally in the standard, the acronym HEIC is used as a brand and in the MIME subtypes image/heic and image/heic-sequence. If the content conforms to certain HEVC profiles, more specific brands can be used: HEIX for Main 10 of HEVC, HEIM for Main profile, and HEIS for Main profile of L-HEVC.
A HEIC photo takes up about half the space of an equivalent quality JPEG file. The initial HEIF specification already defined the means of storing HEVC-encoded intra images and HEVC-encoded image sequences in which inter prediction is applied in a constrained manner.
HEVC image players are required to support rectangular cropping and rotation by one, two, and three quarter-turns. The primary use case for the mandatory support for rotation by 90 degrees is for images where the camera orientation is incorrectly detected or inferred. The rotation requirement makes it possible to manually adjust the orientation of a still image or an image sequence without needing to re-encode it. Cropping enables the image to be re-framed without re-encoding. The HEVC file format also includes the option to store pre-derived images.
Samples in image sequence tracks must be either intra-coded images or inter-picture predicted images with reference to only intra-coded images. These constraints of inter-picture prediction reduce the decoding latency for accessing any particular image within a HEVC image sequence track.
The .heic and .heics file name extensions are conventionally used for HEVC-coded HEIF files. Apple products, for instance, will only produce files with these extensions, which indicate clearly that the data went through HEVC encoding.

AVCI: AVC in HEIF

is an older encoding format for video and images, first standardized in 2003.
It is also specified as a codec to be supported in HEIF in normative Annex 5 to ISO/IEC 23008-12.
The registered MIME types are image/avci for still images and image/avcs for sequences. The format is simply known as AVCI.
Apple products support playback of AVC-encoded .avci still image files and .avcs image sequence files but will only generate .heic files.

AVIF: AV1 in HEIF

is a video encoding format that is intended to be royalty-free, developed by the Alliance for Open Media. AV1 Image File Format is an image format based on this codec.
The registered MIME type is image/avif for both still images and image sequences, and .avif is the file name extension.

JPEG compression formats in HEIF files

The original JPEG standard is the most commonly used and widely supported lossy image coding format. It was first released in 1992 by ITU-T and ISO/IEC. Although Annex H to ISO/IEC 23008-12 specifies JPEG as a possible format for HEIF coded image data, it is used in HEIF only for thumbnails and other secondary images. Therefore, neither a dedicated MIME subtype nor a special file extension is available for storage of JPEG files in HEIF container files.
Several other compression formats defined by the JPEG group can be stored in HEIF files:
  • Part 16 of the JPEG 2000 standard suite defines how to store JPEG 2000 images in HEIF container files. Part 2 of the JPEG 2000 suite also defines a different format for storing JPEG 2000 images in files that is also based on ISOBMFF.
  • Annex F of the JPEG XR image coding standard defines how to store JPEG XR images in HEIF container files. Annex A of JPEG XR also defines a different file format for storing JPEG XR images in files that is TIFF-based, and Part 2 of the JPEG 2000 suite also supports a third file format for storing JPEG XR images in files that is based on ISOBMFF.
  • JPEG XS has its HEIF container support defined in ISO/IEC 21122-3.
In 2017, Apple announced that it would adopt HEIC as the default image format in its new operating systems, gradually replacing JPEG.

WXAM, SharpP

The proprietary image format WXAM developed by Tencent is apparently based upon HEVC, as is SharpP, which was developed by their SNG division. However, their container format may not be HEIF-compatible. In March 2017, SharpP switched to AVS2 and was renamed TPG.

Support

  • Nokia provides an open source C++ HEIF decoder, that also has a Java API.
  • The open source library "libheif" supports reading and writing HEIF files. From version 1.8.0, both reading and writing HEIC and AVIF are supported.
  • An image codec called CopyTrans HEIC, which is free for personal use and available for Windows versions 7 through 10, supports opening HEIF files in Windows Photo Viewer without the Microsoft codec installed.

    Operating systems

  • Windows 10 version 1803 and later, version 1903 and later : is needed to read and write files that use the HEIF format. is needed to play and produce HEVC-encoded video content. A small amount of money is charged for the use of the HEVC codec, whereas support for the generic HEIF format and the AVC and AV1 extensions are free.
  • Windows 11: since 22H2, Windows 11 has HEIF Image Extension built-in by default.
  • macOS High Sierra and later Since macOS Mojave, Apple uses HEIF in creating the Dynamic Desktop feature.
  • iOS 11 and later iOS 16 and later AVIF
  • Apple supports playback of .heif for still image files and .heifs for image sequence files created on other devices that are encoded using any codec, provided that codec is supported by the operating system.
  • Android 8 and later, Android 10 and later, Android 12 and later. Android 13 and higher support 10-bit camera output.
  • Ubuntu 20.04 and later
  • Debian 10.13 or later
  • Fedora 36 or later