AS ISO IEC 12089 pdf download

AS ISO IEC 12089 pdf download.Information technology—Computer graphics and image processing—Encoding for the Image Interchange Facility (IIF)
1 Scope
This International Standard defines the encoding rules which shall apply to the representation of IPIIF image data. The IPIIF data format is defined in ISO/IEC 12087-3, called ,Image Interchange Facility (IIF)“It is Part 3 of the Image Processing and Interchange International Standard, defined in ISO/IEC 12087. The IPI-IF facilitates the interchange of digital images. It consists of two major parts: (1) the IPIIF data format (IIF-DF) definition, whose syntax is described using ASN.1; (2) the IPIIF gateway definition, whose functionality is described by an application programmers interface. The IPI-IIF is based on thc definition describcd in Part I, Common Architecture for Ilmaging (CAI) of the ISO/IEC 12087. . Due to the fact that the syntax of the IIF-DF is expressed using the Abstract Syntax Notation One (ASN.1), defined by ISO/IEC 8824, this standard makes use of the Basic Encoding Rule.s (BER) for ASN.I, by referring to ISO/IEC 8825 for the definition of encoding rules. . NOTE – A rationale for the introduction of new encoding rules in addition to those defined by the BER is given in clause 4. Reference shall be made to this International Standard, and its definitions shall be employed, whenever images are interchanged, according to the IIF-DF, defined in ISO/IEC 12087-3.
4 Encoding rules for the IIF syntax entities
The encoding of syntax entities shall conform to the Basic Encoding Rules (BER) for ASN.1 – ISO/IEC 8825. NOTE- Using the BER encoding overheads may occur. In particular, the encoding of a large pixel data field can produce couisiderabie space andi prucessing ine overhead, wien every pixei is represented as an elementary ASN.I data entity, consisting of a .,tag“and a ,length” ficld that procccds the ,value“ficld. For this reason this International Standard describes additional encoding methods that may be applied to pixel fields. These letltols lay neithel be Icgardeu as extensions, nor as changes to the tag-length-value concept of the BER. Instead, they only describe how to interpret the data contained in the clementary ASN.1 type OCTET STRING, when this elementary type was used to encode an entire field of pixel values (instead of just one value). Thus, these encoding ruies may rather be regarded to lie ,n top of” BER encoding/decoding tools. This International Standard defincs additional encodings for sac-ffcient representation of pixel fields. They are outlined in clause 5 in conjunction with additional IIF syntax entities which describe the degree of freedom for the selection of an encoding method.
5 IIF syntax entities for the representation of pixel fields
The syntax is expressed in ASN.I (Abstract Syntax Notation One), according to ISO/IEC Standard 8824, “Specification of Abstract Syntax Notation One (ASN.1).” ASN.1 is a formal description language. It defines a set of primitive data types, such as INTEGER, ENUMERATED, and REAL and provides a facility to construct new elements with their owI lyping inherent in the structure using the constructors SEQUENCE, SEQUENCE OF and CHOICE. This allows for new data types to bc dcfined which are uniquely recognisable within an application. To make these definitions more readable, textual labels may be associated with the elements in a constructor type. In order to distinguish different occurrences of the same type within one constructor, various typcs of tags arc 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) is called syntax entity. According to ASN.1, the names of the syntax entities begin with capital ltters. Syntax entities consist of a number of components. According to ASN.I, the component labels begin with lower case letters. In the following, ASN.1 code is indicated by courier font. All syntax rules are preceded by a semantics statement. Some rules are succeeded by constraints statements. The rules are ordered in prefix form.