JFIF

Revision as of 03:54, 5 October 2013

JFIF (JPEG File Interchange Format) is a standard that defines a portable subset of the JPEG file format. Most of the JPEG files in existence conform to JFIF.

JFIF defines JPEG application segments which serve to identify JFIF files, and to store a small amount of metadata: the pixel density, and a thumbnail image.

The presence of a JFIF segment implies that:

• If the image has three components, its color format is YCbCr. If it has one component, its color format is grayscale.
• The image has a particular orientation.
• If the image is subsampled, it uses a particular subsampling position.

JFIF was developed based on a draft version of the JPEG standard, which is how it can predate JPEG's official 1992 publication date.

Disambiguation

Don't confuse JPEG File Interchange Format with JPEG Interchange Format. The former is JFIF; the latter means approximately the same thing as JPEG.

Identification

Valid JFIF files begin with FF D8 FF E0 ?? ?? 'J' 'F' 'I' 'F' 00. Some technically-invalid files exist in which the JFIF segment has been relocated, and for them this signature will not match.

History

• JFIF 1.00 (PRONOM: fmt/42) was the original version.

• JFIF 1.01 (December 10, 1991; PRONOM: fmt/43) may have changed the subsampling position to centered.

• JFIF 1.02 (September 1, 1992; PRONOM: fmt/44) added an optional JFXX segment, capable of storing a compressed thumbnail image.

• JFIF 2.xx (2014?): The Independent JPEG Group plans^[1] to release libjpeg 9a in early 2014, which they say will support something called "JFIF version 2".

Specifications

• JFIF version 1.01
• JFIF version 1.02
• ITU-T Rec. T.871 (not free to download)

References

1. ↑ http://www.infai.org/jpeg/

Links

• Wikipedia article
• JFIF description (Eric Hamilton, 1992-09-01)