image/heif
image/heif-sequence
image/heic
image/heic-sequence
image/avif
High Efficiency Image File Format (HEIF) 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.[1]
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. Such files require less storage space than the equivalent quality JPEG.[2][3]
HEIF files are a special case of the ISO Base Media File Format (ISOBMFF, ISO/IEC 14496-12), 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 (MPEG) and is defined as Part 12 within the MPEG-H media suite (ISO/IEC 23008-12).
The requirements and main use cases of HEIF were defined in 2013.[4][5] The technical development of the specification took about one and a half years and was finalized in the middle of 2015.[6]
Apple was the first major adopter of the format in 2017 with the introduction of iOS 11 using HEIC variant. While HEIC became the default for iPhones, it remains possible to revert the settings to allow photos to be recorded in the more recognizable JPEG format.[7]
Android devices containing the appropriate hardware encoders received support for HEIC files with the release of Android 10 (2019).[8]
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,[9] leading the College Board to request students change the settings to send only JPEG files.[10]
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 8-bit HEIC and not 10-bit or 12-bit HEIC.[11]
Camera hardware (including mobile devices) are increasingly supporting outputting HEIC files and with color depth often higher than 8-bit color.[12]
HEIF files can store the following types of data:[1]
The HEIF container can store the following encodings:
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:
The Multi-Image Application Format (MIAF) 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.[13]
High Efficiency Video Coding (HEVC, ITU-T H.265)[14] 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 (High-Efficiency Image Codec) 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 (Multiview) Main profile, and HEIS for (Scalable) Main (10) profile of L-HEVC.
A HEIC photo takes up about half the space of an equivalent quality JPEG file.[15] The initial HEIF specification already defined the means of storing HEVC-encoded intra images (i-frames) 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.[16]
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.[17] Apple products, for instance,[18] will only produce files with these extensions, which indicate clearly that the data went through HEVC encoding.[2]
Advanced Video Coding (AVC, ITU-T H.264) 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.
image/avci
image/avcs
Apple products support playback of AVC-encoded .avci still image files and .avcs image sequence files[18] but will only generate .heic files.
AV1 is a video encoding format that is intended to be royalty-free, developed by the Alliance for Open Media (AOMedia). AV1 Image File Format (AVIF) is an image format based on this codec.[19]
The registered MIME type is image/avif for both still images and image sequences, and .avif is the file name extension.[20]
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 (and indirectly Motion 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:
In 2017, Apple announced that it would adopt HEIC as the default image format in its new operating systems, gradually replacing JPEG.[28]
The proprietary image format WXAM (or wxHEPC) developed by Tencent (used within, e.g., WeChat) is apparently based upon HEVC,[29] as is SharpP, which was developed by their SNG (Social Network Group) division.[30][31] However, their container format may not be HEIF-compatible. In March 2017, SharpP switched to AVS2[32] and was renamed TPG (Tiny Portable Graphics).[31][33]
As of August 2024[update], only Safari supports HEIC format natively.[52]
For AVIF, Chrome, Firefox and Opera for desktop and Android support it. Safari on iOS 16 and iPadOS 16 supports AVIF format.[53]
HEIF itself is a container that may not be subject to additional royalty fees for commercial ISOBMFF licensees. Note however that Nokia also grants its patents on a royalty-free basis for non-commercial purposes.[83] When containing images and image sequences encoded in a particular format (e.g. HEVC or AVC) its use becomes subject to the licensing of patents on the coding format.[84][85][86]
SharpP工具从17年3月开始，已采用AVS2作为新的内核；17年5月正式对外推出基于AVS2的图片格式，联合北大、AVS组织一起完善相关规范，并命名为TPG（Tiny Portable Graphics）
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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.
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.