Sustainability of Digital Formats
Planning for Library of Congress Collections
Sustainability of Digital Formats
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| Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact | |
| Full name | JPEG File Interchange Format, Version 1.02 |
| Description | JFIF is a minimal file format that enables JPEG bitstreams to be exchanged between a wide variety of platforms and applications. It does not include any of the advanced features (like tagged headers) found in the TIFF specification. JFIF conforms to the interchange format syntax specified in JPEG Standard (ISO/IEC 10918-1, Annex B); its only additional requirement is the mandatory presence of the application segment APP0 marker right after the SOI (Start of Image) marker. (Paraphrased from the specification.) |
| Production phase | May be used in initial-state picture creation; often used for middle- and final-state archiving or end-user delivery. |
| Relationship to other formats | |
| May contain | JPEG_DCT_BL, JPEG DCT Compression Encoding, Baseline |
| May contain | JPEG_DCT_EXT, JPEG DCT Compression Encoding, Extensions |
| LC experience or existing holdings | American Memory and other Library of Congress activities have created and archived extensive numbers of JFIF files. The bitstreams they contain are generally JPEG_DCT_BL (baseline) and the images are generally reduced-data derivatives of uncompressed master images. |
| LC preference | The Library's general preference for still image "masters" is for uncompressed bitstreams, and rich metadata is always welcome. Thus TIFF_UNC_EXIF and TIFF_UNC are preferred. For images only available in lossy compressed form, JPEG_DCT is acceptable; preferred file formats for JPEG_DCT include JPEG_EXIF (rich metadata) and JFIF. Meanwhile, J2K_C_LSY (JPEG 2000 Part 1, Core Coding, Lossy Compression) is an emerging preference for compressed bitmapped still images. |
| Disclosure | Fully disclosed. Developed by Eric Hamilton of C-Cube Microsystems.1 |
| Documentation | Specification available at http://www.jpeg.org/public/jfif.pdf. |
| Adoption | Very widely adopted, reportedly surpassing the use of either "raw" JPEG bitstreams or the SPIFF file format specified in ISO/IEC 10918, part 3. |
| Licensing and patent claims | None on the file format; see JPEG_DCT for patent claims on JPEG encoding. |
| Transparency | Transparent. |
| Self-documentation | Limited but some techical metadata is provided by the application segment APP0, and some can be derived in other ways. For detail, see Action Plan Background: JFIF 1.02 (pp. 3-4) from the Florida Center for Library Automation (FCLA). |
| External dependencies | None. |
| Technical protection considerations | None. |
| Normal rendering for still images | Good support. |
| Clarity (support for high image resolution) | See JPEG_DCT_BL and JPEG_DCT_EXT. According to the SPIFF article in the Encyclopedia of Graphics File Formats, "JFIF took a shortcut by attempting to require that all JFIF images have a gamma of 1.0. That requirement has been widely ignored because many pre-existing images have other gamma values, and, as it turns out, a gamma of around 0.4 to 0.5 is technically superior." SPIFF marks its files with the gamma value. |
| Color maintenance | Support for color space support appears to be more limited than SPIFF; thus no support for sRGB2. ICC Profile version 4.2.0.0 (Specification ICC.1:2004-10, page 70) provides guidance for embedding ICC profiles in JFIF files as application data segments: "APP2 marker is used to introduce the tag . . . ICC tags are thus identified by beginning the data with a special null terminated bytes sequence 'ICC_PROFILE.'"3 |
| Support for graphic effects and typography | No support for vector graphics. |
| Functionality beyond normal image rendering | JFIF files (in version 1.02) can store thumbnails along with a larger image, including a means for defining thumbnails from source images with color space other than 24-bit RGB. |
| Tag type | Value | Note |
| Filename Extension | jpg, jpeg, jpe, jfi, jfif, j, jif, jmh | From the File Extension Source. The extension jpg is most frequently used. |
| Internet Media Type | image/jpeg | From the IETF (Internet Engineering Task Force) RFC 2046. |
| Internet Media Type |
image/jpg application/jpg application/x-jpg | Additional MIME types selected from a larger set found at File Extension Source. |
| Magic numbers | Hex: FF D8 FF E0 xx xx 4A 46 49 46 00 ASCII: ÿØÿà..JFIF. | From Gary Kessler's File Signatures Table. |
| General | Paraphrased from Vanryper Murray's Encylopedia of Graphics File Formats (O'Reilly & Assoc, 1994, ISBN 1565920589): The JPEG bitstream stores 16-bit word values in big-endian format. JPEG data in general is stored as a stream of blocks, and each block is identified by a marker value. The first two bytes of every JPEG stream are the Start Of Image (SOI) marker values FFh D8h. In a JFIF-compliant file there is a JFIF APP0 (Application) marker, immediately following the SOI, which consists of the marker code values FFh E0h and the characters JFIF in the marker data, as described in the next section. In addition to the JFIF marker segment, there may be one or more optional JFIF extension marker segments, followed by the actual image data. |
| History |
URLs
• http://www.jpeg.org/public/jfif.pdf
1From http://www.jpeg.org/jpeg/index.html: "[T]he file format was created originally by Eric Hamilton, the then convenor of JPEG as part of his work at C-Cube Microsystems, and was placed by them into the public domain under the name JFIF (available here in the latest version, 1.02)."
2The color space sRGB, standardized as IEC 61966-2-1, establishes an image viewing environment with a known color temperature (6500 degrees Kelvin) and gamma (2.2), thus increasing the user's ability to maintain color.
3The most effective color maintenance systems rely on the existence of an ICC (International Color Consortium) profile of the capture device, which can then be compared to profiles for output devices, permitting appropriate adjustments of image color.
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