| FreeType font driver for BDF fonts |
| |
| Francesco Zappa Nardelli |
| <francesco.zappa.nardelli@ens.fr> |
| |
| |
| Introduction |
| ************ |
| |
| BDF (Bitmap Distribution Format) is a bitmap font format defined by Adobe, |
| which is intended to be easily understood by both humans and computers. |
| This code implements a BDF driver for the FreeType library, following the |
| Adobe Specification V 2.2. The specification of the BDF font format is |
| available from Adobe's web site: |
| |
| https://adobe-type-tools.github.io/font-tech-notes/pdfs/5005.BDF_Spec.pdf |
| |
| Many good bitmap fonts in bdf format come with XFree86 (www.XFree86.org). |
| They do not define vertical metrics, because the X Consortium BDF |
| specification has removed them. |
| |
| |
| Encodings |
| ********* |
| |
| [This section is out of date, retained for historical reasons. BDF |
| properties can be retrieved with `FT_Get_BDF_Property`, character set ID |
| values with `FT_Get_BDF_Charset_ID`.] |
| |
| The variety of encodings that accompanies bdf fonts appears to encompass the |
| small set defined in freetype.h. On the other hand, two properties that |
| specify encoding and registry are usually defined in bdf fonts. |
| |
| I decided to make these two properties directly accessible, leaving to the |
| client application the work of interpreting them. For instance: |
| |
| |
| #include FT_INTERNAL_BDF_TYPES_H |
| |
| FT_Face face; |
| BDF_Public_Face bdfface; |
| |
| |
| FT_New_Face( library, ..., &face ); |
| |
| bdfface = (BDF_Public_Face)face; |
| |
| if ( ( bdfface->charset_registry == "ISO10646" ) && |
| ( bdfface->charset_encoding == "1" ) ) |
| [..] |
| |
| |
| Thus the driver always exports `ft_encoding_none' as face->charmap.encoding. |
| FT_Get_Char_Index's behavior is unmodified, that is, it converts the ULong |
| value given as argument into the corresponding glyph number. |
| |
| If the two properties are not available, Adobe Standard Encoding should be |
| assumed. |
| |
| |
| Anti-Aliased Bitmaps |
| ******************** |
| |
| The driver supports an extension to the BDF format as used in Mark Leisher's |
| xmbdfed bitmap font editor. Microsoft's SBIT tool expects bitmap fonts in |
| that format for adding anti-aliased them to TrueType fonts. It introduces a |
| fourth field to the `SIZE' keyword which gives the bpp value (bits per |
| pixel) of the glyph data in the font. Possible values are 1 (the default), |
| 2 (four gray levels), 4 (16 gray levels), and 8 (256 gray levels). The |
| driver returns either a bitmap with 1 bit per pixel or a pixmap with 8bits |
| per pixel (using 4, 16, and 256 gray levels, respectively). |
| |
| |
| Known problems |
| ************** |
| |
| - A font is entirely loaded into memory. Obviously, this is not the Right |
| Thing(TM). If you have big fonts I suggest you convert them into PCF |
| format (using the bdftopcf utility): the PCF font drive of FreeType can |
| perform incremental glyph loading. |
| |
| When I have some time, I will implement on-demand glyph parsing. |
| |
| - Except for encodings properties, client applications have no visibility of |
| the PCF_Face object. This means that applications cannot directly access |
| font tables and must trust FreeType. |
| |
| - Currently, glyph names are ignored. |
| |
| I plan to give full visibility of the BDF_Face object in an upcoming |
| revision of the driver, thus implementing also glyph names. |
| |
| - As I have never seen a BDF font that defines vertical metrics, vertical |
| metrics are (parsed and) discarded. If you own a BDF font that defines |
| vertical metrics, please let me know (I will implement them in 5-10 |
| minutes). |
| |
| |
| License |
| ******* |
| |
| Copyright (C) 2001-2002 by Francesco Zappa Nardelli |
| |
| Permission is hereby granted, free of charge, to any person obtaining |
| a copy of this software and associated documentation files (the |
| "Software"), to deal in the Software without restriction, including |
| without limitation the rights to use, copy, modify, merge, publish, |
| distribute, sublicense, and/or sell copies of the Software, and to |
| permit persons to whom the Software is furnished to do so, subject to |
| the following conditions: |
| |
| The above copyright notice and this permission notice shall be |
| included in all copies or substantial portions of the Software. |
| |
| THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, |
| EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF |
| MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. |
| IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY |
| CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, |
| TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE |
| SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. |
| |
| *** Portions of the driver (that is, bdflib.c and bdf.h): |
| |
| Copyright 2000 Computing Research Labs, New Mexico State University |
| Copyright 2001-2002, 2011 Francesco Zappa Nardelli |
| |
| Permission is hereby granted, free of charge, to any person obtaining a |
| copy of this software and associated documentation files (the "Software"), |
| to deal in the Software without restriction, including without limitation |
| the rights to use, copy, modify, merge, publish, distribute, sublicense, |
| and/or sell copies of the Software, and to permit persons to whom the |
| Software is furnished to do so, subject to the following conditions: |
| |
| The above copyright notice and this permission notice shall be included in |
| all copies or substantial portions of the Software. |
| |
| THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL |
| THE COMPUTING RESEARCH LAB OR NEW MEXICO STATE UNIVERSITY BE LIABLE FOR ANY |
| CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT |
| OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR |
| THE USE OR OTHER DEALINGS IN THE SOFTWARE. |
| |
| |
| Credits |
| ******* |
| |
| This driver is based on excellent Mark Leisher's bdf library. If you |
| find something good in this driver you should probably thank him, not |
| me. |