scope:

This standard establishes the requirements to be met by systems complying with NITFS when image data are compressed using the JPEG image compression algorithm as described in DIS 10918-1, Digital Compression and Coding of Continuous-tone Still Images.

This standard provides technical detail of the NITFS compression algorithm designated by the code C3 in the Image Compression field of the National Imagery Transmission Format (NITF) file image subheader, JPEG, for both eight- and 12-bit gray scale imagery and 24-bit color imagery. It also provides the required default quantization tables for use in Secondary Imagery Dissemination Systems (SIDS) complying with NITFS.

This standard is applicable to the Intelligence Community and the Department of Defense. It is mandatory for all Secondary Imagery Dissemination Systems in accordance with the memorandum by the Assistant Secretary of Defense for Command, Control, Communications, and Intelligence ASD (C³I) Subject: National Imagery Transmission Format Standard (NITFS), 12 August 1991. This standard shall be implemented in accordance with the Joint Interoperability and Engineering Organization (JIEO) Circular 9008 and MIL-HDBK-1300. New equipment and systems, those undergoing major modification, or those capable of rehabilitation shall conform to this standard.

The minimum compliance requirements for implementation of this compression algorithm are defined in JIEO Circular 9008.

This standard establishes the requirements for the communication or storage for interchange of image data in compressed form. Each type of operation defined by this standard consists of three parts:

a. The compressed data interchange format (which defines the image data field of the NITF file format).

b. The encoder.

c. The decoder.

This standard currently defines three types of operation:

a. Type 1 - 8-bit sample precision gray scale sequential Discrete Cosine Transform (DCT) with Huffman coding. b. Type 2 - 24-bit color, 8-bit sample precision per component, sequential DCT with Huffman coding. c. Type 3 - 12-bit sample precision gray scale sequential DCT with Huffman coding. d. Types 4-N - To Be Revised (TBR).

Additional types of conforming JPEG encoding methods and extensions to the conforming interchange format are expected to be added in future versions of this standard as soon as technical work codifies their requirements and validates fitness for use.