1、 INTERNATIONAL STANDARD ISO/IEC 14496-28:2012 TECHNICAL CORRIGENDUM 2 Published 2014-07-01 INTERNATIONAL ORGANIZATION FOR STANDARDIZATION ORGANISATION INTERNATIONALE DE NORMALISATION INTERNATIONAL ELECTROTECHNICAL COMMISSION COMMISSION LECTROTECHNIQUE INTERNATIONALEInformation technology Coding of a
2、udio-visual objects Part 28: Composite font representation TECHNICAL CORRIGENDUM 2: Changes and clarifications of CFR element descriptions Technologies de linformation Codage des objets audiovisuels Partie 28: Reprsentation de la police de caractres composite RECTIFICATIF TECHNIQUE 2: Modifications
3、et prcisions de descriptions dlments CFR Technical Corrigendum 2 to ISO/IEC 14496-28:2012 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology, Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information. This corrigendum aims to clarify the meaning
4、 and use of certain Composite Font elements and explain their relationships within the components of the document. In clause 2 “Normative references“ add the new normative reference to the ISO/IEC 14496-22 “Open Font Format“ In subclause 5.1 “High-level overview“ replace the text description with th
5、e following: A CFR resource consists of a single PosingFont element, and its Components element specifies an arbitrary number of ComponentDef or LanguagePreferredList elements. It may contain a number of optional elements (such as Name and FontMetrics elements) which provide additional information a
6、bout the CFR resource and its metrics. Whenever an optional element is missing from the CFR, or if there are optional ICS 35.040 Ref. No. ISO/IEC 14496-28:2012/Cor.2:2014(E) ISO/IEC 2014 All rights reserved Published in Switzerland ISO/IEC 14496-28:2012/Cor.2:2014(E) 2 ISO/IEC 2014 All rights reserv
7、edattributes that are missing from any of the elements the corresponding information expected to be provided by the missing optional elements and attributes shall be inherited from the first component font specified by either ComponentDef or LanguagePreferredList element. Please note that the choice
8、 of the first component font specified by a LanguagePreferredList element may be dependent on users language preferences and, therefore, font metrics and other values inherited from the first component font may also change depending on user language preferences. A CFR resource can be instantiated as
9、 a standalone file or resource, and it can be referenced by another CFR resource. Examples of Composite Font Representation are presented in Annex B. In subclause 5.3 “The Name element“ replace the first paragraph of the element description with the following: Optional. Each instance of the Name ele
10、ment specifies an attribute that is equivalent to a specific name table string of an sfnt resource. The original set of name table entries shall be inherited from the first component font; however, whenever an attribute is present, it will effectively override a particular name table entry with the
11、string defined by the particular instance of the element. In subclause 5.4 “The FontMetrics element“ replace the first paragraph of the element description with the following: Optional. The FontMetrics element specifies various line-layout attributes that apply globally to the CFR resource. All attr
12、ibutes of the element are optional, if the element or any of its attributes are not present in the CFR resource definitions but the missing font metrics data is deemed essential for proper layout the corresponding font metrics entry from the first component font shall be used. Since the choice of th
13、e first component font may vary based on the user language preferences, it is important to make sure that either language-specific components have matching font metrics or that the attributes and their values provided by the FontMetrics element define a complete overriding set of parameters to avoid
14、 the unwanted layout effects. In subclause 5.4 “The FontMetrics element“ replace the attribute definitions of the element with the following: unitsPerEm = “string“ Optional. A virtual UPM (Units Per Em) of the CFR resource expressed as an integer. Its only purpose is to facilitate the correct interp
15、retation of the additional attributes defined by this element, the actual UPM values of the component fonts defined by the CFR may differ both between the component fonts and from the CFR FontMetrics value. The values of the additional attributes are based on this UPM value. macStyle = “string“ Opti
16、onal. The head.macStyle value expressed as a 16-digit bit array, see ISO/IEC 14496-22 for detailed descriptionof the attribute value. ascender = “string“ Optional. When provided, this value of ascender will be used by the host rendering system implementations and will override the default value of e
17、ach component font it is the CFR authors responsibility to make sure that the value is suitable for all component fonts on various host rendering systems. If the value of ascender is not defined, the host rendering system will use the first, highest priority component font to determine the ascender
18、value according to the algorithm defined in the ISO/IEC 14496-22 (in the “Baseline to Baseline Distances“ section of the “Recommendations“ clause.). ISO/IEC 14496-28:2012/Cor.2:2014(E) ISO/IEC 2014 All rights reserved 3descender = “string“ Optional. When provided, this value of descender will be use
19、d by the host rendering system implementations and will override the default value of each component font it is the CFR authors responsibility to make sure that the value is suitable for all component fonts on various host rendering systems. If the value of descender is not defined, the host renderi
20、ng system will use the first, highest priority component font to determine the descender value according to the algorithm defined in the ISO/IEC 14496- 22 (in the “Baseline to Baseline Distances“ section of the “Recommendations“ clause.). linegap = “string“ Optional. When provided, this value of lin
21、egap will be used by the host rendering system implementations and will override the default value of each component font it is the CFR authors responsibility to make sure that the value is suitable for all component fonts on various host rendering systems. If the value of linegap is not defined, th
22、e host rendering system will use the first, highest priority component font to determine the linegap value according to the algorithm defined in the ISO/IEC 14496-22 (in the “Baseline to Baseline Distances“ section of the “Recommendations“ clause.). xMaxExtent = “string“ Optional. The value of the f
23、ormula MAX (minLeftSideBearing + (xMax - xMin) expressed as an integer. yMaxExtent = “string“ Optional. The value of the formula MAX (minTopSideBearing + (yMax - yMin) expressed as an integer. caretSlopeRise = “string“ Optional. The value, expressed as an integer, is used to calculate the slope of t
24、he cursor according to the formula (caretSlopeRise caretSlopeRun). Use the value 1 for a vertical cursor, which is best for horizontal writing mode. caretSlopeRun = “string“ Optional. The value, expressed as an integer, is used to calculate the slope of the cursor according to the formula (caretSlop
25、eRise caretSlopeRun). Use the value 0 for a vertical cursor, which is best for horizontal writing mode. caretOffset = “string“ Optional. The amount by which a slanted highlight on a glyph needs to be shifted to produce the best appearance, expressed as an integer. Use the value 0 for non-slanted fon
26、ts. vertCaretSlopeRise = “string“ Optional. The value, expressed as an integer, is used to calculate the slope of the cursor according to the formula (vertCaretSlopeRise vertCaretSlopeRun). Use the value 0 for a horizontal cursor, which is best for vertical writing mode. vertCaretSlopeRun = “string“
27、 Optional. The value, expressed as an integer, is used to calculate the slope of the cursor according to the formula (vertCaretSlopeRise vertCaretSlopeRun). Use the value 1 for a horizontal cursor, which is best for vertical writing mode. ISO/IEC 14496-28:2012/Cor.2:2014(E) 4 ISO/IEC 2014 All rights
28、 reservedvertCaretOffset = “string“ Optional. The amount by which a slanted highlight on a glyph needs to be shifted to produce the best appearance, expressed as an integer. Use the value 0 for non-slanted fonts. italicAngle = “string“ Optional. The italic angle in counter-clockwise degrees from the
29、 vertical expressed as a floating point number. Upright text should be set to 0, and text that leans to the right should be set to a negative value. In subclause 5.4 “The FontMetrics element“ add a last paragraph explaining the relationship between CFR font metrics and individual component font metr
30、ics that may have been modified using the Matrix element: Please note that each individual component font glyphs and metrics can be adjusted using transform defined by the Matrix element (see subclause 5.11). When CFR metrics are calculated based on the component font metrics the results of the appl
31、ied transforms shall be taken into account. Please also note that each individual component font may use unitsPerEm value that is different from the one specified by the FontMetrics element. As such, the numerical font metric values specified for each component font maybe defined using different coo
32、rdinate systems and shall be recalculated accordingly to determine the correct CFR metrics. In subclause 5.5 “The Components element“ add a paragraph to the description of the element with the following text: Please note that users language settings only has an effect on the order of the LanguagePre
33、ferredComponentDef elements defined as part of the LanguagePreferredList (see subcaluse 5.7 for detailed description), it does not affect the priority order defined by the Components element. In subclause 5.7 “The LanguagePreferredList element“ replace the third paragraph in description of the eleme
34、nt with the following text: The users language setting determines which LanguagePreferredComponentDef element to use first, but it does not modify the priority order of the elements. When a character that is not supported by the font specified by that LanguagePreferredComponentDef element is encountered, the ordering of the LanguagePreferredComponentDef elements is significant, and the first LanguagePreferredComponentDef element that supports the character is used.
