JPEG XL: The Next Generation of Image Codecs

Oct 19, 2021
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JPEG has dominated the world of image compression since its inception 27 years ago. During the same period, a variety of media encodings for other files, particularly for videos and sounds, arose and grew increasingly refined. There were a couple of major reasons why no format could ever replace JPEG during this time. One was a lack of essential progressive migration features, while the other was psychovisual performance in professional quality photography.

JPEG XL Codec was announced in April 2018 to be an advanced version of JPEG that improved several elements such as compression efficiency and image size. It also offered a lot of new features that were immensely beneficial for compressing professional high-quality images.


Key Features of Codec

JPEG XL Codec has all the great features of Google PIK and FUIF. It also offers many new features that make this format the future of image codecs. Some of the most anticipated features are discussed below.

Universal Codec

JPEG XL supports a wide range of image types, including standard photographs, illustrations, cartoons, computer-generated pictures, logos, user-interface elements, screenshots, maps, medical imagery, images for printing, such as Cyan Magenta Yellow Black (CMYK) with additional spot colors, scientific photographs, satellite photos, game visuals, big images (gigapixel or even terapixel), tiny icons, images with alpha transparency, selection masks, or depth information, layered images, and In terms of workflows, JPEG XL can be used not just as a web-delivery format, but also as local storage and exchange format for authoring workflows that require quick and effective lossless compression and a high bit depth. JPEG XL completely outperforms JPEG, PNG, GIF, WebP, and TIFF in terms of functionality and compression

Default Quality

By default, the JPEG XL reference encoder (cjpegxl) generates a well-compressed image that is indistinguishable from (or, in some situations, identical to) the original. Other image formats, on the other hand, usually contain an encoder with which you may select a quality preset, where quality is not truly defined perceptually. As a result, one image may appear good as a quality-60 JPEG while another may still exhibit noticeable artifacts as a quality-90 JPEG. Internally, JPEG XL makes use of XYB, a unique, perceptually motivated color space. The YCbCr color space is still used by the majority of other codecs, usually with chroma subsampling. JPEG XL, with its more precise color management, is better at preventing color banding issues—even in challenging darks.

Best Codec for Responsive Images

It would be preferable, especially for web delivery, to avoid having to save and offer numerous copies of the same image based on the viewer’s viewport width. An option to progressively decode images is also useful, displaying a low-quality image placeholder when just a few hundred bytes have arrived and adding more detail when the remainder of the data arrives. JPEG XL supports both of these amazing features making it the best choice for responsive designs and images.

Check this link to learn about progressive JPEG XL images.

Spotlight Benefits of JPEG XL

Although JPEG XL has many advantages over previous generations of codecs, some of them truly make this codec a game-changer. Here are some of the highlight pros of JPEG XL Codec.

A Complete Package

JPEG XL aspired to be a full-featured image codec, supporting all of the features that modern image formats offer. As a result, JPEG XL may support an arbitrary number of channels, including alpha and depth channels, it also supports parallel, progressive, and partial decoding features. Furthermore, JPEG XL offers multiple animation frames encoding, with various alternatives for how each frame should be blended with the preceding ones: they can be totaled, replaced the complete frame or a sub-rectangle, or alpha-blended. JPEG XL also has a fully lossless option as well as a responsive-by-design mode.

Royalty-Free

The JPEG XL contributors have agreed to license the reference implementation under the Apache 2.0 license. Therefore, in addition to being Free and Open-Source Software (FOSS), JPEG XL includes a royalty-free patent award. Other image file formats, such as HEIC, HEVC, and AVIF, do not have this independence. Even though being royalty-free was the main goal of the Alliance for Open Media, which launched AV1, yet it is still unclear to what extent AV1 is truly royalty-free.

Fast and Two-Way Transcription

Existing JPEG files can be easily and reversibly converted to JPEG XL without any complexities. This was the most highly demanded feature that other image formats, such as JPEG 2000, JPEG XR, WebP, HEIC, and AVIF, lacked. These formats transcode the image into other formats by first decoding the image to pixels and then re-encoding those pixels with the other format. This is an irreversible procedure that results in a loss of generation. JPEG XL offers an easy transition from JPEG to any format without the need for extra processing. You don’t have to save both the old and new files, resulting in faster and better image compression.

Easy Encoding & Decoding

Modern video codecs such as AV1 and HEVC can be encoded and decoded in software, but the computational cost is significant, especially for well-optimized encoding. To efficiently implement such codecs, dedicated hardware is recommended (if not needed). In comparison, JPEG XL can be easily and quickly encoded or decoded in software on current hardware.

Availability of JPEG XL

JPEG XL was initially released in December 2019. It is still in developer trial status but you can test the codec in some popular browsers like Chrome, Mozilla, Opera, and Safari by manually enabling it. Full software support for JPEG XL in apps and platforms will still take time and effort. To check the current status of the codec check here.

Dethroning the old JPEG will be a difficult task, as proven by previous failed attempts. Let’s hope that whenever it becomes a standard, JPEG XL will also last for 30 years!

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