1、INCITS/ISO/IEC 9636-4-1991(R1997)(formerly ANSI/ISO/IEC 9636-4-1991 (R1997) for Information Technology -Computer Graphics -Interfacing Techniques forDialogues with Graphical Devices (CGI) -Functional Specification -Part 4: SegmentsAmericanNationalStandardApproval of an American National Standard req
2、uires review by ANSI that therequirements for due process, consensus, and other criteria for approval havebeen met by the standards developer.Consensus is established when, in the judgment of the ANSI Board of StandardsReview, substantial agreement has been reached by directly and materiallyaffected
3、 interests. Substantial agreement means much more than a simplemajority, but not necessarily unanimity. Consensus requires that all views andobjections be considered, and that a concerted effort be made toward theirresolution.The use of American National Standards is completely voluntary; their exis
4、tencedoes not in any respect preclude anyone, whether he has approved the standardsor not, from manufacturing, marketing, purchasing, or using products, processes,or procedures not conforming to the standards.The American National Standards Institute does not develop standards and will inno circumst
5、ances give an interpretation of any American National Standard.Moreover, no person shall have the right or authority to issue an interpretation ofan American National Standard in the name of the American National StandardsInstitute. Requests for interpretations should be addressed to the secretariat
6、 orsponsor whose name appears on the title page of this standard.CAUTION NOTICE: This American National Standard may be revised orwithdrawn at any time. The procedures of the American National StandardsInstitute require that action be taken periodically to reaffirm, revise, or withdrawthis standard.
7、 Purchasers of American National Standards may receive currentinformation on all standards by calling or writing the American National StandardsInstitute.Published byAmerican National Standards Institute11 West 42nd Street, New York, New York 10036Copyright 1991 by Information Technology Industry Co
8、uncil (ITI)All rights reserved.These materials are subject to copyright claims of International Standardization Organization (ISO),International Electrotechnical Commission (IEC), American National Standards Institute (ANSI), andInformation Technology Industry Council (ITI). Not for resale. No part
9、of this publication may bereproduced in any form, including an electronic retrieval system, without the prior written permission of ITI.All requests pertaining to this standard should be submitted to ITI, 1250 Eye Street NW, Washington, DC20005.Printed in the United States of AmericaANSI/ISO/IEC 963
10、6-4-l 991 Redesignation of ANSI X3.161 (never published) American National Standard for Information Technology - Computer Graphics - Interfacing Techniques for Dialogues with Graphical Devices (CGI)- Functional Specification - Part 4: Segments Secretariat Computer and Business Equipment Manufacturer
11、s Association Approved August 6,1992 American National Standards Institute, Inc. _- - ULlmr-zn A.7 _i.e,., r i-L-IL-eLh Foreword (This foreword is not part of American National Standard ANSI/ISO/IEC 9636-4-l 991. This document is identical to ISO/IEC 9636-4-l 991, and the following five paragraphs a
12、re the original foreword as it appeared in that document.) IS0 (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the specialized system for worldwide standardization. National bodies that are members of IS0 or IEC participate in the dev
13、elopment of International Standards through technical committees established by the respective organization to deal with particular fields of technical activity. IS0 and IEC technical committees collaborate in fields of mutual interest. Other international organizations, governmental and non-governm
14、ental, in liaison with IS0 and IEC, also take part in the work. In the field of information technology, IS0 and IEC have established a joint technical committee, ISO/IEC JTC 1. Draft International Standards adopt- ed by the joint technical committee are circulated to national bodies for voting. Publ
15、ication as an International Standard requires approval by at least 75% of the national bodies casting a vote. International Standard ISO/IEC 9636-4 was prepared by Joint Technical Committee ISO/IEC JTC 1, information technology. ISO/IEC 9636 consists of the following parts, under the general title I
16、nformation technology - Computer graphics - interfacing techniques for dialogues with graphical devices (CGI) - Functional specification: - Part 7: Overview, profiles, and conformance - Part 2: Control - Part 3: Output - Part 4: Segments - Part 5: Input and echoing - Part 6: Raster Annexes A and B f
17、orm an integral part of this part of ISO/IEC 9636. Annexes C and D are for information only. Requests for interpretation, suggestions for improvement or addenda, or defect reports are welcome. They should be sent to the X3 Secretariat, Computer and Business Equipment Manufacturers Association, 1250
18、Eye Street, NW, Suite 200, Washington, DC 20005. This standard was processed and approved for submittal to ANSI by Accredited Standards Committee on Information Processing Systems, X3. Committee approval of the standard does not necessarily imply that all committee members voted for its approval. At
19、 the time it approved this standard, the X3 Committee had the following members: (Position Vacant), Chair Donald C. Loughry, Vice-Chair Joanne Flanagan, Secretary Organization Represented Name of Representative Allen-Bradley Company . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20、 . . . . . . . . . . . . . . . . . . . Ronald Reimer Joe Lenner (Ah.) American Library Association . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Paul Peters iv Organization Represented Name of Representative American Nuclear Society . . . . . . . . . . . .
21、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Geraldine C. Main Sally Hartzell (Alt.) AMP, Inc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Edward Kelly Edward Miko
22、ski (Alt.) Apple Computer, Inc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Karen Higginbottom Association of the Institute for Certification of Computer Professionals (AICCP) . . . . . . . . . . . . . . . . . . . . . . . . . . .
23、. . . . Kenneth Zemrowski Eugene Dwyer (Alt.) ATi .- Id, . . . . , .- _ Lqa-J.-.-r.:.z Introduction This part of ISO/IEC 9636 describes the functions of the Computer Graphics Inter;w_UjirU-iCLLIIL_i- 2 ISO/IEC 96364 : 1991 (E) Concepts Creating segments CREmE - A level of TIME ORDER - REOPEN is simi
24、lar to TIME ORDER, except that a change in the effective relative display priority is possible for a segment if subsequently reopened; - A level of OTHER indicates that there is no guaranteed effective telative display priority bebaviour. The SEGMENT DISPLAY PRIORITY function is used to change the d
25、isplay priority of a segment. When a segments Display Priority is changed, the segments display is based on the Implicit Segment Regeneration Mode and the new Display Priority. (See 3.4.) 3.3.6 Segment pick priority The Pick Priority attribute of a segment is used to resolve the picking of segments
26、which overlap. If two or more segments overlap and the pick location is within the intersection of these segments, the segments picked will be one, or more, of those with the highest pick priority. The returned list of pick values (see 54.1 and PICK input in ISO/IEC 9636-5) corresponds to all those
27、segments having the highest identical pick priority and are retumed in order of decreasing display priority. 5 ISO/IEC 96364 : 1991 (E) Concepts Segment attributes 3.3.7 Segment transformation The Segment Transformation attribute specif=s a coordinate transformation to be applied to the graphic obje
28、cts contained in the segment. This transformation allows scaling, translation, and rotation of segments. The segment transformation is a transformation of VDC space to VDC space and is distinct from the VDC-to-Device Mapping (see ISO/lEC 9636-2.3.3). which is a transformation of VDC space to DC spac
29、e. The Segment Transformation attribute is set by the SEGMENT TRANSFORMATION function. This function simply replaces the Segment Transformation attribute associated with a particular segment A segment transformation is composed of a 2x2 scaling and rotation portion and a 2x1 translation portion. The
30、 default Segment Transformation for each segment is the identity transformation. The Segment Transformation attribute is associated with the graphic objects of a segment when they enter into the graphic object pipeline. This associated transformation is then applied during the rendering of the graph
31、ic objects. A graphic object is transformed by the transformation resulting from the concatenation of the segment transformation and the objects transformation attribute before the application of the VDC-to-Device Mapping. The method of concatenation is such that the fina effect during rendering is
32、as if the objects transformation attribute was applied first, followed by application of the segment tmnsfommtion. This transformation is applied to the graphic objects VDC point data and all associated attributes having VDC pmmakzations, with the exception of the associated clip rectangle. NGTE - I
33、f the client wishes to accumulate or concatenate transformations for the purpose of setting the Segment Transformation attribute, it is necessary to do this above the CGI. The use of segment transformations may produce cootdinates that cannot he expressed within the VDC range; this is handled in an
34、implementationdependent way. 3.4 Segment display 3.4.1 Introduction Segment display is the process which produces a visible image on a drawing surface from the graphic objects in a segment The functions COPY SEGMENT and DRAW ALL SEGMENTS provide for the display of segments, individually and collecti
35、vely. Segments may also he displayed implicitly, under some circumstances, without using the above functions (see 3.4.2). In addition to the attributes associated with the graphic objects stored in segments, the Highlighting, Visibility, Display Riority. and Segment Transformation attributes of segm
36、ents affect the appearance of the displayed segment. Some devices czumot immediately change a picture. A plotter for example can only add to a picture; the plotter would need to advance the paper and redraw the picture to show the effect of a change of Segment Transformation. Similarly, a change of
37、a segments Display priority attribute might cause different sections of a picture to become visible or obscured, and Visibility and Highlighting attributes may also cause the picture to alter. On devices which cannot erase or change part of a picture, Implicit Segment Regeneration Mode of SUPPRESSED
38、 is more efficient in terms of time and material. Implicit Segment Regeneration Mode in combination with the Visibility attribute gives the client the ability to accumulate picture changes. At some later time, the client can explicitly utilixe PREPARE DRAWING SURFACE and DRAW ALL SEGMENTS. 3.4.2 Seg
39、ment regeneration Conceptually, the contents of segment storage, along with the values of various state list and bundle table entries, describe a certain picture. In addition to tlte stored graphic objects, the state list information which may affect the appearance of the picture is shown in table 1
40、. Segment creation or deletion, as well as dynamic changes to any of the state lit entries in table 1, may affect the accuracy of the rendered picture (i.e. whether or not the current, rendered picture mpresentation accurately reflects the picture described in segment storage and state lists). The p
41、rocess of bringing the rendered picture representation to a state consistent with the current contents of segment storage and state lists is referred to as regeneration. 6 ISO/IEC 9636-4 : 1991 (E) Segment display Concepts Table 1 - State list information which may affect the appearance of the pictu
42、re VDC-to-Device Mapping Colour table entries Background Colour Bundled primitive attribute values (depending on associated ASFs) Pattern table entries Segment Attributes: Display Priority Visibility Highlighting Segment Transformation When there is a discrepancy between the current contents of the
43、drawing surface and the described picture, a regeneration is pending. The Segment State List includes a Regeneration Pending entry, which indicates whether or not any such discrepancy currently exists. Changes to the picture, or to the state list information that controls the appearance of the pictu
44、re (see table 1) may cause the Regeneration Pending entry to be set to YES. If there is any visible picture discrepancy, the implementation shall set the entry to YES. The implementation may also set the entry to YES in case that a change effects no visible discrepancy, but the implementation is not
45、 able to determine that there is no discrepancy. Once set, Regeneration Pending remains set until an implicit regeneration or until the function RESET REGENERATION PENDING has been invoked. There are a number of CGI functions which may change the contents of the drawing surface in such a way that it
46、 no longer accurately reflects the contents of segment storage, but do not cause Regeneration Pending to be set. This set of functions includes COPY SEGMENT when there is no segment open and all graphic primitive functions executed when there is no segment open (thereby creating non-retained data).
47、It also includes bitblts, PIXEL ARRAY, DRAWING BITMAP, and PREPARE DRAWING SURFACE. It is the clients responsibility to be aware of the implications of the use of these functions in conjunction with segments and handle any desired regeneration explicitly. For performance reasons, it may he preferabl
48、e to batch a number of picture changes and then perform a single regeneration. A means to control regeneration behaviour is provided by the Implicit Segment Regeneration Mode entry in tbe Segment State List. When Implicit Segment Regeneration Mode is SUPPRESSED, the Virtual Device will not perform a
49、ny regeneration even if one is pending. For particular devices, wme changes may not necessitate a regeneration, An important (and common) example concerns changes to the Colour Table on a raster device. Typically, such devices implement a colour table in hardware. Changing the colour representation associated with a given colour index immediately (and retroactively) affects all pixels drawn with that index. No regeneration process is required to bring the picture up to date. For each state list entry corresponding to information in table 1, a Dynamic Modification Ac
