1 FreeType font driver for BDF fonts 2 3 Francesco Zappa Nardelli 4 <francesco.zappa.nardelli (a] ens.fr> 5 6 7 Introduction 8 ************ 9 10 BDF (Bitmap Distribution Format) is a bitmap font format defined by Adobe, 11 which is intended to be easily understood by both humans and computers. 12 This code implements a BDF driver for the FreeType library, following the 13 Adobe Specification V 2.2. The specification of the BDF font format is 14 available from Adobe's web site: 15 16 https://www.adobe.com/content/dam/acom/en/devnet/font/pdfs/5005.BDF_Spec.pdf 17 18 Many good bitmap fonts in bdf format come with XFree86 (www.XFree86.org). 19 They do not define vertical metrics, because the X Consortium BDF 20 specification has removed them. 21 22 23 Encodings 24 ********* 25 26 The variety of encodings that accompanies bdf fonts appears to encompass the 27 small set defined in freetype.h. On the other hand, two properties that 28 specify encoding and registry are usually defined in bdf fonts. 29 30 I decided to make these two properties directly accessible, leaving to the 31 client 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 49 Thus the driver always exports `ft_encoding_none' as face->charmap.encoding. 50 FT_Get_Char_Index's behavior is unmodified, that is, it converts the ULong 51 value given as argument into the corresponding glyph number. 52 53 If the two properties are not available, Adobe Standard Encoding should be 54 assumed. 55 56 57 Anti-Aliased Bitmaps 58 ******************** 59 60 The driver supports an extension to the BDF format as used in Mark Leisher's 61 xmbdfed bitmap font editor. Microsoft's SBIT tool expects bitmap fonts in 62 that format for adding anti-aliased them to TrueType fonts. It introduces a 63 fourth field to the `SIZE' keyword which gives the bpp value (bits per 64 pixel) of the glyph data in the font. Possible values are 1 (the default), 65 2 (four gray levels), 4 (16 gray levels), and 8 (256 gray levels). The 66 driver returns either a bitmap with 1 bit per pixel or a pixmap with 8bits 67 per pixel (using 4, 16, and 256 gray levels, respectively). 68 69 70 Known 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 78 When 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 95 License 96 ******* 97 98 Copyright (C) 2001-2002 by Francesco Zappa Nardelli 99 100 Permission is hereby granted, free of charge, to any person obtaining 101 a copy of this software and associated documentation files (the 102 "Software"), to deal in the Software without restriction, including 103 without limitation the rights to use, copy, modify, merge, publish, 104 distribute, sublicense, and/or sell copies of the Software, and to 105 permit persons to whom the Software is furnished to do so, subject to 106 the following conditions: 107 108 The above copyright notice and this permission notice shall be 109 included in all copies or substantial portions of the Software. 110 111 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 112 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 113 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 114 IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY 115 CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, 116 TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE 117 SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. 118 119 *** Portions of the driver (that is, bdflib.c and bdf.h): 120 121 Copyright 2000 Computing Research Labs, New Mexico State University 122 Copyright 2001-2002, 2011 Francesco Zappa Nardelli 123 124 Permission is hereby granted, free of charge, to any person obtaining a 125 copy of this software and associated documentation files (the "Software"), 126 to deal in the Software without restriction, including without limitation 127 the rights to use, copy, modify, merge, publish, distribute, sublicense, 128 and/or sell copies of the Software, and to permit persons to whom the 129 Software is furnished to do so, subject to the following conditions: 130 131 The above copyright notice and this permission notice shall be included in 132 all copies or substantial portions of the Software. 133 134 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 135 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 136 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 137 THE COMPUTING RESEARCH LAB OR NEW MEXICO STATE UNIVERSITY BE LIABLE FOR ANY 138 CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT 139 OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR 140 THE USE OR OTHER DEALINGS IN THE SOFTWARE. 141 142 143 Credits 144 ******* 145 146 This driver is based on excellent Mark Leisher's bdf library. If you 147 find something good in this driver you should probably thank him, not 148 me. 149
