High Efficiency Image File Format
High Efficiency Image File Format (HEIF) is a file format for individual images and image sequences. It was developed by the Moving Picture Experts Group (MPEG) and is defined by MPEG-H Part 12 (ISO/IEC 23008-12).
|Internet media type||
|Uniform Type Identifier (UTI)||public.heif, public.heic|
|Developed by||Moving Picture Experts Group (MPEG)|
|Type of format||Image Container Format|
|Standard||ISO/IEC CD 23008-12|
The HEIF specification also defines the means of storing High Efficiency Video Codec (HEVC)-encoded intra images and HEVC-encoded image sequences in which inter prediction is applied in a constrained manner.
HEIF files are compatible with the ISO Base Media File Format (ISOBMFF, ISO/IEC 14496-12) and can also include other media streams, such as timed text and audio.
Some usage scenarios that are facilitated by HEIF are described below:
Digital cameras and smartphonesEdit
To save storage space, HEIF-encapsulated HEVC-coded images can be used for compressing the full-resolution images while keeping a lower-resolution JPEG copy (e.g. at 4K resolution or below) for on-screen displaying purposes.
Digital cameras and smartphones can use HEIF to achieve single-file packaging of burst photos, focal stacks, and exposure stacks. Similarly, simultaneously captured video and still images can be stored in the same HEIF file. HEIF also enables storage of any image collections into a single file, which can be shared easily.
Web pages and Internet-connected image applicationsEdit
The picture element of HTML5.2 provides the capability of indicating multiple alternatives for the same image, out of which the web browser can select the one that best suits its purpose. A motivation for web pages and connected applications to start using HEIF is to reduce the web page and image content download times.
Changing of the orientation and cropping are basic features of HEIF and require no re-encoding of the images. Additionally, HEIF introduces a framework for non-destructive editing operations, which can be specified by external specifications. This feature can be used by image editing applications so that the editing instructions are kept in the same file as the original image.
HEIF files can store the following types of data:
- Image Items: storage of individual images, image properties and thumbnail(s).
- Image Derivations: derived images are generated during run-time based on descriptions such as rotation, grid and overlay. These images depend on other images stored in the HEIF file. The storage overhead of derived images is small.
- Image Sequences: storage of multiple time-related and/or temporally predicted images (like a burst-photo shot or cinemagraph animation), 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 even when tens of images are stored in the same HEIF file.
- Auxiliary Image Items: storage of image data which complements another image item. An alpha plane or a depth map are examples for such images. 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.
HEVC Image File FormatEdit
- HEVC image players are required to support rectangular cropping and rotation by 90, 180, and 270 degrees. The primary use case for the mandatory support for rotation by 90 degrees is for the photo shooting situations in which the camera orientation is incorrectly detected or concluded. This requirement makes it possible to manually adjust the image or image sequence orientation afterwards without the need for re-encoding the image or image sequence. Similarly, cropping may be useful to enable post-shooting zoom without the need for re-encoding. As rotation by 90, 180, or 270 degrees as well as cropping are mandatory for all HEVC image file players, it is guaranteed that re-encoding is not required to carry out these operations.
- 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 an HEVC image sequence track.
HEIF itself is a container, but when containing HEVC encoded images, HEIF becomes subject to HEVC patent licensing. Generally, lawful use of a patented invention requires the patent holder's permission in countries where the patent is in force (see patent infringement).
- "Requirements for still image coding using HEVC | MPEG". mpeg.chiariglione.org. Retrieved 2015-11-25.
- "Requirements for HEVC image sequences | MPEG". mpeg.chiariglione.org. Retrieved 2015-11-25.
- "Evidence motivates MPEG to launch new standardization effort for HDR".
- Hollister, Sean (June 5, 2017). "Apple answers iPhone storage woes with smaller photos, videos". CNET. CBS Interactive. Retrieved September 30, 2017.
- Snell, Jason (September 20, 2017). "iOS 11: HEVC, HEIF, and what you need to know about these new video and photo formats". Macworld. Retrieved September 30, 2017.
- Shu, Lee (September 19, 2017). "Here’s what HEIF and HEVC are, and why they’ll improve your iPhone with iOS 11". Digital Trends. Retrieved September 30, 2017.
- M. M. Hannuksela; E. B. Aksu; V. K. Malamal Vadakital; J. Lainema. "Overview of the High Efficiency Image File Format". JCT-VC document JCTVC-V0072, Oct. 2015.
- "macOS High Sierra tech preview: A quick look at the stuff you can’t see". 2017-06-19. Retrieved 4 July 2017.
If there’s one major downside to both HEVC and HEIF, it’s that they’re covered by patents that may need to be licensed for use in various apps and services.
- "Converting a JPEG to the new HEIF format". Retrieved 4 July 2017.
HEIF and HEVC are extensively covered by patents, which means there could be legal implications to implementing HEIF support, particularly in paid software or a hardware product.