1 FreeType font driver for BDF fonts 2 3 Francesco Zappa Nardelli 4 <francesco.zappa.nardelli@ens.fr> 5 6 7Introduction 8************ 9 10BDF (Bitmap Distribution Format) is a bitmap font format defined by Adobe, 11which is intended to be easily understood by both humans and computers. 12This code implements a BDF driver for the FreeType library, following the 13Adobe Specification V 2.2. The specification of the BDF font format is 14available from Adobe's web site: 15 16 https://www.adobe.com/content/dam/acom/en/devnet/font/pdfs/5005.BDF_Spec.pdf 17 18Many good bitmap fonts in bdf format come with XFree86 (www.XFree86.org). 19They do not define vertical metrics, because the X Consortium BDF 20specification has removed them. 21 22 23Encodings 24********* 25 26The variety of encodings that accompanies bdf fonts appears to encompass the 27small set defined in freetype.h. On the other hand, two properties that 28specify encoding and registry are usually defined in bdf fonts. 29 30I decided to make these two properties directly accessible, leaving to the 31client application the work of interpreting them. For instance: 32 33 34 #include FT_INTERNAL_BDF_TYPES_H 35 36 FT_Face face; 37 BDF_Public_Face bdfface; 38 39 40 FT_New_Face( library, ..., &face ); 41 42 bdfface = (BDF_Public_Face)face; 43 44 if ( ( bdfface->charset_registry == "ISO10646" ) && 45 ( bdfface->charset_encoding == "1" ) ) 46 [..] 47 48 49Thus the driver always exports `ft_encoding_none' as face->charmap.encoding. 50FT_Get_Char_Index's behavior is unmodified, that is, it converts the ULong 51value given as argument into the corresponding glyph number. 52 53If the two properties are not available, Adobe Standard Encoding should be 54assumed. 55 56 57Anti-Aliased Bitmaps 58******************** 59 60The driver supports an extension to the BDF format as used in Mark Leisher's 61xmbdfed bitmap font editor. Microsoft's SBIT tool expects bitmap fonts in 62that format for adding anti-aliased them to TrueType fonts. It introduces a 63fourth field to the `SIZE' keyword which gives the bpp value (bits per 64pixel) of the glyph data in the font. Possible values are 1 (the default), 652 (four gray levels), 4 (16 gray levels), and 8 (256 gray levels). The 66driver returns either a bitmap with 1 bit per pixel or a pixmap with 8bits 67per pixel (using 4, 16, and 256 gray levels, respectively). 68 69 70Known problems 71************** 72 73- A font is entirely loaded into memory. Obviously, this is not the Right 74 Thing(TM). If you have big fonts I suggest you convert them into PCF 75 format (using the bdftopcf utility): the PCF font drive of FreeType can 76 perform incremental glyph loading. 77 78When I have some time, I will implement on-demand glyph parsing. 79 80- Except for encodings properties, client applications have no visibility of 81 the PCF_Face object. This means that applications cannot directly access 82 font tables and must trust FreeType. 83 84- Currently, glyph names are ignored. 85 86 I plan to give full visibility of the BDF_Face object in an upcoming 87 revision of the driver, thus implementing also glyph names. 88 89- As I have never seen a BDF font that defines vertical metrics, vertical 90 metrics are (parsed and) discarded. If you own a BDF font that defines 91 vertical metrics, please let me know (I will implement them in 5-10 92 minutes). 93 94 95License 96******* 97 98Copyright (C) 2001-2002 by Francesco Zappa Nardelli 99 100Permission is hereby granted, free of charge, to any person obtaining 101a copy of this software and associated documentation files (the 102"Software"), to deal in the Software without restriction, including 103without limitation the rights to use, copy, modify, merge, publish, 104distribute, sublicense, and/or sell copies of the Software, and to 105permit persons to whom the Software is furnished to do so, subject to 106the following conditions: 107 108The above copyright notice and this permission notice shall be 109included in all copies or substantial portions of the Software. 110 111THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 112EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 113MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 114IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY 115CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, 116TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE 117SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. 118 119*** Portions of the driver (that is, bdflib.c and bdf.h): 120 121Copyright 2000 Computing Research Labs, New Mexico State University 122Copyright 2001-2002, 2011 Francesco Zappa Nardelli 123 124Permission is hereby granted, free of charge, to any person obtaining a 125copy of this software and associated documentation files (the "Software"), 126to deal in the Software without restriction, including without limitation 127the rights to use, copy, modify, merge, publish, distribute, sublicense, 128and/or sell copies of the Software, and to permit persons to whom the 129Software is furnished to do so, subject to the following conditions: 130 131The above copyright notice and this permission notice shall be included in 132all copies or substantial portions of the Software. 133 134THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 135IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 136FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 137THE COMPUTING RESEARCH LAB OR NEW MEXICO STATE UNIVERSITY BE LIABLE FOR ANY 138CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT 139OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR 140THE USE OR OTHER DEALINGS IN THE SOFTWARE. 141 142 143Credits 144******* 145 146This driver is based on excellent Mark Leisher's bdf library. If you 147find something good in this driver you should probably thank him, not 148me. 149