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SPIFF, Still Picture Interchange File Format

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Table of Contents
• Identification and description
• Local use
• Sustainability factors
• Quality and functionality factors
• File type signifiers
• Notes
• Format specifications
• Useful references
Format Description Properties
• ID: fdd000019
• Short name: SPIFF
• Content categories: still image
• Format category: File format
• Last significant update: 2007-02-08
• Draft status: Full

Identification and description Explanation of format description terms

Full nameAnnex F of ISO/IEC 10918-3 (Part 3 of the JPEG_DCT specification). Still Picture Interchange File Format (SPIFF).
Description File format that enables JPEG and JBIG (bitonal) bitstreams to be exchanged between a wide variety of platforms and applications. According to the specification, SPIFF "is designed to incorporate functionality found in some (ad hoc) image file formats (such as JFIF) . . . . it is intended that transcoding between any of these file formats and SPIFF should be simple." (p. 39) May contain a profile identifier to distinguish, say, baseline from progressive-encoded images.
  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 containJPEG_DCT_BL, JPEG DCT Compression Encoding, Baseline
  May containJPEG_DCT_EXT, JPEG DCT Compression Encoding, Extensions
  May containJBIG1, JBIG1 Bitonal Image Encoding
  May containJBIG2, JBIG2 Bitonal Image Encoding
  May contain MR (Modified READ) and MMR (Modified Modified READ) compression, not documented at this Web site; MMR is used by ITU_G4, ITU-T "Group 4" FAX Compression (T.6)

Local use Explanation of format description terms

LC experience or existing holdingsNone.
LC preferenceThe 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.

Sustainability factors Explanation of format description terms

DisclosureFully disclosed. Developed by the Joint Photographic Experts Group (JPEG), formally known as ISO/IEC JTC 1/SC 29/WG 10.
  Documentation ISO/IEC 10918-3 (part 3), Annex F. Also published as ITU-T Recommendation T.84.
AdoptionAppears not to be widely adopted; most producers create JFIF files, which conform to the general file interchange specifications in ISO/IEC 10918-1 (part 1).
  Licensing and patent claimsNone on the file format; see JPEG_DCT for patent claims on JPEG encoding.
TransparencyTransparent.
Self-documentation Limited techical metadata is provided in a file header (specification pp. 41-45). The specification also lists a set of descriptive-data tags (e.g., title, creator, copyright, etc.) in a discussion of directory entries. (pp. 45 ff.) See also the useful explanations in the SPIFF article in the Encyclopedia of Graphics File Formats
External dependenciesNone.
Technical protection considerationsNone.

Quality and functionality factors Explanation of format description terms

Normal rendering for still imagesGood support.
Clarity (support for high image resolution) See JPEG_DCT_BL and JPEG_DCT_EXT. SPIFF marks its files with the gamma value, in contrast to JFIF. The maximum image size if 4Gx4G pixles or 64Kx64K pixels for non-tiled baseline JPEG. According to the SPIFF article in the Encyclopedia of Graphics File Formats, SPIFF files can support the following forms of compression: MR, MMR, JBIG (certainly JBIG1 and possibly JBIG2—editor), JPEG, and uncompressed.
Color maintenanceThe header does not support the recording of an ICC profile for the capture device.1 The header can contain a code for color spaces, including bi-level, three YCbCr spaces associated with ITU-T specifications BT 709 and BT 601-1, grayscale, PhotoYCC, RGB, CMY, CMYK, YCCK, and CIELab (specification, p. 44); the list does not include sRGB.2
Support for graphic effects and typographyNo support for vector graphics.
Functionality beyond normal image renderingCan store thumbnails along with a larger image.

File type signifiers Explanation of format description terms

Tag typeValueNote
Filename Extensionjpg, jpegFrom the SPIFF article in the Encyclopedia of Graphics File Formats: "The SPIFF specification does not define a standard file extension . . . for SPIFF files. IJG [Independent JPEG Group] recommends that the extension ".JPG" . . . be used for SPIFF files containing lossy (DCT) JPEG-compressed data."3
Filename Extensionspf, spiff From the SPIFF article in the Encyclopedia of Graphics File Formats: "IJG recommends that the extension . . . ".SPF" be used for all [non-JPEG] variants of SPIFF. (Of course, the JBIG community might prefer a ".JBG" extension for SPIFF-JBIG files.)" Meanwhile, the File Extension Source (as consulted in February 2007), in an "unverified" entry, offers the extension spiff.
Internet Media Typeimage/jpegFrom the SPIFF article in the Encyclopedia of Graphics File Formats: "IJG recommends that . . . 'JPEG' type indicator be used for SPIFF files containing lossy (DCT) JPEG-compressed data."
Magic numbersHex: FF D8 FF E8 xx xx 53 50 49 46 46 00
ASCII: ÿØÿè..SPIFF		Derived from the specification.

Notes Explanation of format description terms

GeneralParaphrased 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 

Format specifications Explanation of format description terms

URLs

Print
• ISO/IEC 10918-3 (part 3), Annex F.

Useful references

URLs
• JHOVE's JPEG page (http://hul.harvard.edu/jhove/jpeg-hul.html)
• SPIFF article in the Encyclopedia of Graphics File Formats (http://www.fileformat.info/format/spiff/)
Print
• Murray, Vanryper. Encylopedia of Graphics File Formats, Sebastopol, California: O'Reilly & Assoc, 1994. (ISBN 1565920589)

1The 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.

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 when compared to unqualified RGB.

3The Encyclopia continues, "The file extension .JPG is already commonly used for JFIF-format JPEG files. However, properly written JFIF-compatible software should read SPIFF-JPEG files without difficulty. The SPIFF format has been carefully designed to make this possible by defining the magic numbers and length fields to make the SPIFF header look like a series of JPEG APPn markers, which old JPEG decoders will just ignore."


Last Updated: 03/ 7/2007

 
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