HEIF - New Standard Image Storage Format for iOS and MacOS

Original author: Brian Buck
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This year, Apple’s operating systems have changed the default save image format. With the release of iOS 11 and MacOS High Sierra, millions of users of apple giant products have been given the opportunity to use the new HEIF image storage format. It replaced the good old JPEG, although many do not know what happened. According to Apple's calculations, users should get significant savings in disk space (up to 50%) due to greater compression efficiency with better picture quality.


For the past quarter century, JPEG has been the industry standard for storing lossy compression images. The format developed in 1992 since then has been supported by most manufacturers of equipment and software for capturing and processing images. However, as digital cameras and display screens move toward ultra-high 5K resolutions, the need for more efficient compression algorithms and support for alternative features has led Apple to find a modern replacement for the outdated JPEG standard.


They became High Efficiency Image Format, or abbreviated HEIF. Files of this format on Apple operating systems received the .heic extension, although .heif is used more often by other manufacturers.


A few facts about HEIF:


  • In 2013, the HEIF format was proposed by the Moving Picture Experts Group (MPEG), it was defined as part of the MPEG-H Part 12 (ISO / IEC 23008-12) standard. For a year and a half, its technical development continued, which was completed by 2015.
  • HEIF itself is a container format consisting of Exif metadata with additional sections for XMP and MPEG-7
  • In addition to metadata, the HEIF container contains one or more images or a sequence of images encoded using the HEVC's High Efficiency Video Coding standard, which is better known as the H.265 standard. Due to this, users will receive memory savings both locally and in the cloud. If multiple images are packaged in a HEIF container, the file size will be significantly smaller than storing multiple JPEGs representing the same image or set of images. Multiple images and videos can be simultaneously packaged in a HEIF container.
  • Unlike JPEG, HEIF can contain several images used for different occasions. For example, the main full-size image can be represented by primary, auxiliary and thumbnail images.
  • Ancillary images may have an alpha channel.
  • There is built-in support for overlays.
  • A HEIF container may contain equivalent images, such as an alternative to lower resolution. An example is a browser that downloads a low-resolution image on a slow communication channel or display detection <4K. HTML 5.2 provides support for such cases.
  • Support for the simultaneous storage of data compressed with and without lossy (lossy and lossless). Photographers will appreciate saving raw and compressed photos in one container.
  • HEIF provides tools for non-destructive editing operations that can be defined by external specifications. This function can be used by image editing applications because editing instructions are stored in the same file as the original image.
  • HEIF also supports transparency and image color of up to 16 bits, compared to 8-bit color depth in JPEG. In practice, this means that HEIF can capture the entire extended color range provided by the 10-bit color output of digital cameras, eliminating unwanted artifacts.

Now that you’ve learned a little more about HEIF, let's talk about the HEVC or H.265 encoding standard.


In a nutshell, the HEVC standard supports efficient compression for full-size images along with predictive sequencing and add-ons to support other media streams such as synchronized text and audio.


The format provides tremendous opportunities - it’s not only a potential replacement for animated GIFs, but also an improvement on Apple’s live photos, which opens the door to other functions, such as built-in editing and full playback control.


In addition, the HEVC supports rectangular cropping and rotation of 90 degrees without the need for re-encoding of the image or sequence of images. This makes it possible to write effective image processing code on mobile devices, which will lead to significant battery savings. In fact, Apple devices with an A9 chip or higher will benefit from hardware acceleration for encoding and decoding HEIF files.


HEIF Support for Apple Products


image

Left image in HEIF format, right JPEG

Changing Apple's default image file format to HEIF will save space in the user's local photo albums and in iCloud. The example shows an image encoded in both JPEG and saved in HEIF format. The most obvious thing we see when viewing metadata is a reduction in file size of almost 1MB. You can also notice that the HEIF image is sharper, while the JPEG image is blurry enough.


Automatic conversion to JPEG will be supported for some time, as most platforms and services require the JPEG format. For example, a user can attach HEIF photos to an email, and iOS will automatically transcode them to JPEG.


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