ISO IEC 12089:1997 pdf download – lnformation technology – Computergraphics and image processing 一 ncoding for the image lnterchange Facility(F)

ISO IEC 12089:1997 pdf download – lnformation technology – Computergraphics and image processing 一 ncoding for the image lnterchange Facility(F).
4 Encoding rules for the hF syntax entities
The encoding of syntax entities shall conform to the Basic Encoding Ruks (BER) for’ ASNI – ISO/TEC 8X25.
NOTE. Using the BER encoding overheads may occur. In particular, the encoding of a large pixel data field can produce considerable space and processing time overhead, when every pixel is rcpresentcd as an clcmcntary ASN. I data emily. consisting of a ..tag’ and a ,,length” field that proceeds the ..value” field.
For this reason this International Standard describes additional encoding methods that may be applied to pixci
fields. These methods may neither be regarded as extensions, nor as changes to the ag-Iength-’daluc conccpt of the BER Instead, they only describe how to interpret the data contained in the elementary ASN.I type OCTET STRING, when this elementary type was used to encode an entire field of pixel values (instead of just one value these encoding rules may rather be regarded to lie .,of top or’ HER encoding/decoding tools
This International Standard defines additional encodings for space-efficient representation of pixel fields. They are outlined in clause 5 in conjunction with additional hF syntax CnTilies which describe the degree of freedom for the selection of an encoding method.
5 HIF syntax entities for the representation of pixel fields
The syntax is expressed in ASN.1(Abstract Syntax Notation One)，according to ISO/IEC Standard 8824,”Specification of Abstract Syntax Notation One (ASN.1).”ASN.l is a formal description language. It defines aset of primitive data types，such as INTEGER，ENUMERATED, and REAL and provides a facility to constructnew elements with their own typing inherent in the structure using the constructors SEQUENCE,SEQUENCBoF and CHOICE. This allows for new data types to be defined which are uniquely recognisable within anapplication.To make these definitions more readable, textual labels may be associated with the elements in aconstructor type. In order to distinguish different occurrences of the same type within one constructor,varioustypes of tags are provided that may be associated with the constructor’s elements.
Within the semantic description each element (which is either a primitive data type or a constructed type) iscalled syntax entity.According to ASN.1, the names of the syntax entities begin with capital letters. Syntaxentities consist of a number of components.According to ASN.1, the component labels begin with lower caseletters.
In the following，ASN.1 code is indicated by courier font.All syntax rules are preceded by a semanticsstatement.Some rules arc succceded by constraints statcmcnts.The rulcs are ordered in prefix form.