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JPEG File Interchange Format, Version 1.02

Standard color space

The color space to be used is YCbCr as defined by CCIR 601 (256 levels). The RGB
components calculated by linear conversion from YCbCr shall not be gamma corrected
(gamma = 1.0). If only one component is used, that component shall be Y.

APP0 marker used to identify JPEG FIF

The APP0 marker is used to identify a JPEG FIF file. The JPEG FIF APP0 marker is
mandatory right after the SOI marker.

The JFIF APP0 marker is identified by a zero terminated string: "JFIF". The APP0 can be
used for any other purpose by the application provided it can be distinguished from the
JFIF APP0.

The JFIF APP0 marker provides information which is missing from the JPEG stream:
version number, X and Y pixel density (dots per inch or dots per cm), pixel aspect ratio
(derived from X and Y pixel density), thumbnail.

APP0 marker used to specify JFIF extensions

Additional APP0 marker segment(s) can optionally be used to specify JFIF extensions. If
used, these segment(s) must immediately follow the JFIF APP0 marker. Decoders should
skip any unsupported JFIF extension segments and continue decoding.

The JFIF extension APP0 marker is identified by a zero terminated string: "JFXX". The
JFIF extension APP0 marker segment contains a 1-byte code which identifies the
extension. This version, version 1.02, has only one extension defined: an extension for
defining thumbnails stored in formats other than 24-bit RGB.

APP0 marker used for application-specific information

Additional APP0 marker segments can be used to hold application-specific information
which does not affect the decodability or displayability of the JFIF file. Application-
specific APP0 marker segments must appear after the JFIF APP0 and any JFXX APP0
segments. Decoders should skip any unrecognized application-specific APP0 segments.

Application-specific APP0 marker segments are identified by a zero terminated string which
identifies the application (not "JFIF" or "JFXX"). This string should be an organization
name or company trademark. Generic strings such as dog, cat, tree, etc. should not be
used.