Saturday, August 05, 2006
CID-Keyed font
TTF算是一種CID font 嗎?
===================================================================
from: Adobe《Adobe CMap and CIDFont Files Specification》---June 11, 1993
A CID-keyed font is a font program that maps character codes to CIDs, and uses CIDs to access glyph data.(下圖為清楚的示意圖)
character code →[CMap resource]→CID→[CID Font resource]→glyph data
(下圖)Figure 2 is a data flow diagram of the internal organization of a CIDFont.
In VM, the CMap resource produces a character ID for use by the CIDFont resource. The character ID acts as an index into the CIDMap, which is in turn used to locate other pieces of information. Each interval of the CIDMap also has two parts: (1) an index into the
FDArray, which is an array of font dictionaries. (2) an offset into the charstring data. Charstring data, subroutine information (if any), and data from the appropriate member of the FDArray of font dictionaries, are required to rasterize a glyph.
===================================================================
from: Adobe Tecnique Notes #5092 ---Sep. 12, 1994
用來理解TTF檔中 cmap 表的使用方式, 以及 Font developer 如何使用 CID 來發展新字型
* Abstrasct
同一個字元不同的編碼方式(Big5, Unicode...)下, 會有不同的 encoding id, 而我們將任一語言的常用字元編成一個 character collection, 並給每個字元一個 id (即CID), 如此一來, 不同編碼下的同一字元即可對應至相同 CID , 使開發新字型更為方便.
* Character ID (CID) numbers is are used to index and access the characters in the font. They are based on a predefined and named character collection, and a specific ordering of that collection.
- New Counter Control Hints
One type of hint information that is paticularly important for complex CJK characters is the
Counter Control hint ( counters are the white spaces between stems in a character). It helps insure that counters and overall proportions are rendered as accurately as possible, subject to the number of pixels available for a given size and resolution. (幫助字元在任何大小和解悉度的環境中都能儘量以正常地"形"顯示出來)
* CID-Keyed Font Components
one or more CMap files and a CIDFont file.
- Character collection
A character collection consists of an ordered set of all characters needed to support one or more popular character sets for a particular language. The order of the characters in the Character Collection determines the CID number for each character.
Adobe Systems publishes character collections for Chinese, Japanese, and Korean fonts; 字型發展者即可利用這些現成的 character collection 來發展其字型
- CMap files
CMap (Character Map) files specify the correspondence between a character code and the CID number used to access the character description in the CIDFont file.
- CIDFont Files (字型開發者要做的就是這個囉~)
The CIDFont file contains the characters in the font, each of which is a computer language procedure that “draws” a given character shape for either display on the screen or for printing. The CIDFont file is the only component that most font developers will have to produce.
The CIDFont file also contains tables that help the interpreter locate the required characters and associated data, as well as additional information called hints which help the interpreter to create high-quality images of the characters at small sizes or at low resolutions.
===================================================================
* from IBM
Figure 2. One CMap and two CIDFonts or two CMaps and one CIDFont. This figure was created by Adobe Systems, Inc.
===================================================================
from: Adobe《Adobe CMap and CIDFont Files Specification》---June 11, 1993
A CID-keyed font is a font program that maps character codes to CIDs, and uses CIDs to access glyph data.(下圖為清楚的示意圖)
character code →[CMap resource]→CID→[CID Font resource]→glyph data
(下圖)Figure 2 is a data flow diagram of the internal organization of a CIDFont.
In VM, the CMap resource produces a character ID for use by the CIDFont resource. The character ID acts as an index into the CIDMap, which is in turn used to locate other pieces of information. Each interval of the CIDMap also has two parts: (1) an index into the
FDArray, which is an array of font dictionaries. (2) an offset into the charstring data. Charstring data, subroutine information (if any), and data from the appropriate member of the FDArray of font dictionaries, are required to rasterize a glyph.
===================================================================
from: Adobe Tecnique Notes #5092 ---Sep. 12, 1994
用來理解TTF檔中 cmap 表的使用方式, 以及 Font developer 如何使用 CID 來發展新字型
* Abstrasct
同一個字元不同的編碼方式(Big5, Unicode...)下, 會有不同的 encoding id, 而我們將任一語言的常用字元編成一個 character collection, 並給每個字元一個 id (即CID), 如此一來, 不同編碼下的同一字元即可對應至相同 CID , 使開發新字型更為方便.
* Character ID (CID) numbers is are used to index and access the characters in the font. They are based on a predefined and named character collection, and a specific ordering of that collection.
- New Counter Control Hints
One type of hint information that is paticularly important for complex CJK characters is the
Counter Control hint ( counters are the white spaces between stems in a character). It helps insure that counters and overall proportions are rendered as accurately as possible, subject to the number of pixels available for a given size and resolution. (幫助字元在任何大小和解悉度的環境中都能儘量以正常地"形"顯示出來)
* CID-Keyed Font Components
one or more CMap files and a CIDFont file.
- Character collection
A character collection consists of an ordered set of all characters needed to support one or more popular character sets for a particular language. The order of the characters in the Character Collection determines the CID number for each character.
Adobe Systems publishes character collections for Chinese, Japanese, and Korean fonts; 字型發展者即可利用這些現成的 character collection 來發展其字型
- CMap files
CMap (Character Map) files specify the correspondence between a character code and the CID number used to access the character description in the CIDFont file.
- CIDFont Files (字型開發者要做的就是這個囉~)
The CIDFont file contains the characters in the font, each of which is a computer language procedure that “draws” a given character shape for either display on the screen or for printing. The CIDFont file is the only component that most font developers will have to produce.
The CIDFont file also contains tables that help the interpreter locate the required characters and associated data, as well as additional information called hints which help the interpreter to create high-quality images of the characters at small sizes or at low resolutions.
===================================================================
* from IBM
Figure 2. One CMap and two CIDFonts or two CMaps and one CIDFont. This figure was created by Adobe Systems, Inc.
===> posted by BASSHOU @ 7:56 AM 
