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code pour la generation de captchas
author goldfinger
date Thu, 11 Feb 2010 05:09:46 -0500
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1 Bitstream Vera Fonts - April 16, 2003
2 =====================================
3
4 The version number of these fonts is 1.10 to distinguish them from the
5 beta test fonts.
6
7 Note that the Vera copyright is incorporated in the fonts themselves.
8 The License field in the fonts contains the copyright license as it
9 appears below. The TrueType copyright field is not large enough to
10 contain the full license, so the license is incorporated (as you might
11 think if you thought about it) into the license field, which
12 unfortunately can be obscure to find. (In pfaedit, see: Element->Font
13 Info->TTFNames->License).
14
15 Our apologies for it taking longer to complete the fonts than planned.
16 Beta testers requested a tighter line spacing (less leading) and Jim
17 Lyles redesigned Vera's accents to bring its line spacing to more
18 typical of other fonts. This took additional time and effort. Our
19 thanks to Jim for this effort above and beyond the call of duty.
20
21 There are four monospace and sans faces (normal, oblique, bold, bold
22 oblique) and two serif faces (normal and bold). Fontconfig/Xft2 (see
23 www.fontconfig.org) can artificially oblique the serif faces for you:
24 this loses hinting and distorts the faces slightly, but is visibly
25 different than normal and bold, and reasonably pleasing.
26
27 On systems with fontconfig 2.0 or 2.1 installed, making your sans,
28 serif and monospace fonts default to these fonts is very easy. Just
29 drop the file local.conf into your /etc/fonts directory. This will
30 make the Bitstream fonts your default fonts for all applications using
31 fontconfig (if sans, serif, or monospace names are used, as they often
32 are as default values in many desktops). The XML in local.conf may
33 need modification to enable subpixel decimation, if appropriate,
34 however, the commented out phrase does so for XFree86 4.3, in the case
35 that the server does not have sufficient information to identify the
36 use of a flat panel. Fontconfig 2.2 adds Vera to the list of font
37 families and will, by default use it as the default sans, serif and
38 monospace fonts.
39
40 During the testing of the final Vera fonts, we learned that screen
41 fonts in general are only typically hinted to work correctly at
42 integer pixel sizes. Vera is coded internally for integer sizes only.
43 We need to investigate further to see if there are commonly used fonts
44 that are hinted to be rounded but are not rounded to integer sizes due
45 to oversights in their coding.
46
47 Most fonts work best at 8 pixels and below if anti-aliased only, as
48 the amount of work required to hint well at smaller and smaller sizes
49 becomes astronomical. GASP tables are typically used to control
50 whether hinting is used or not, but Freetype/Xft does not currently
51 support GASP tables (which are present in Vera).
52
53 To mitigate this problem, both for Vera and other fonts, there will be
54 (very shortly) a new fontconfig 2.2 release that will, by default not
55 apply hints if the size is below 8 pixels. if you should have a font
56 that in fact has been hinted more agressively, you can use fontconfig
57 to note this exception. We believe this should improve many hinted
58 fonts in addition to Vera, though implemeting GASP support is likely
59 the right long term solution.
60
61 Font rendering in Gnome or KDE is the combination of algorithms in
62 Xft2 and Freetype, along with hinting in the fonts themselves. It is
63 vital to have sufficient information to disentangle problems that you
64 may observe.
65
66 Note that having your font rendering system set up correctly is vital
67 to proper judgement of problems of the fonts:
68
69 * Freetype may or may not be configured to in ways that may
70 implement execution of possibly patented (in some parts of the world)
71 TrueType hinting algorithms, particularly at small sizes. Best
72 results are obtained while using these algorithms.
73
74 * The freetype autohinter (used when the possibly patented
75 algorithms are not used) continues to improve with each release. If
76 you are using the autohinter, please ensure you are using an up to
77 date version of freetype before reporting problems.
78
79 * Please identify what version of freetype you are using in any
80 bug reports, and how your freetype is configured.
81
82 * Make sure you are not using the freetype version included in
83 XFree86 4.3, as it has bugs that significantly degrade most fonts,
84 including Vera. if you build XFree86 4.3 from source yourself, you may
85 have installed this broken version without intending it (as I
86 did). Vera was verified with the recently released Freetype 2.1.4. On
87 many systems, 'ldd" can be used to see which freetype shared library
88 is actually being used.
89
90 * Xft/X Render does not (yet) implement gamma correction. This
91 causes significant problems rendering white text on a black background
92 (causing partial pixels to be insufficiently shaded) if the gamma of
93 your monitor has not been compensated for, and minor problems with
94 black text on a while background. The program "xgamma" can be used to
95 set a gamma correction value in the X server's color pallette. Most
96 monitors have a gamma near 2.
97
98 * Note that the Vera family uses minimal delta hinting. Your
99 results on other systems when not used anti-aliased may not be
100 entirely satisfying. We are primarily interested in reports of
101 problems on open source systems implementing Xft2/fontconfig/freetype
102 (which implements antialiasing and hinting adjustements, and
103 sophisticated subpixel decimation on flatpanels). Also, the
104 algorithms used by Xft2 adjust the hints to integer widths and the
105 results are crisper on open source systems than on Windows or
106 MacIntosh.
107
108 * Your fontconfig may (probably does) predate the release of
109 fontconfig 2.2, and you may see artifacts not present when the font is
110 used at very small sizes with hinting enabled. "vc-list -V" can be
111 used to see what version you have installed.
112
113 We believe and hope that these fonts will resolve the problems
114 reported during beta test. The largest change is the reduction of
115 leading (interline spacing), which had annoyed a number of people, and
116 reduced Vera's utility for some applcations. The Vera monospace font
117 should also now make '0' and 'O' and '1' and 'l' more clearly
118 distinguishable.
119
120 The version of these fonts is version 1.10. Fontconfig should be
121 choosing the new version of the fonts if both the released fonts and
122 beta test fonts are installed (though please discard them: they have
123 names of form tt20[1-12]gn.ttf). Note that older versions of
124 fontconfig sometimes did not rebuild their cache correctly when new
125 fonts are installed: please upgrade to fontconfig 2.2. "fc-cache -f"
126 can be used to force rebuilding fontconfig's cache files.
127
128 If you note problems, please send them to fonts at gnome dot org, with
129 exactly which face and size and unicode point you observe the problem
130 at. The xfd utility from XFree86 CVS may be useful for this (e.g. "xfd
131 -fa sans"). A possibly more useful program to examine fonts at a
132 variety of sizes is the "waterfall" program found in Keith Packard's
133 CVS.
134
135 $ cvs -d :pserver:anoncvs@keithp.com:/local/src/CVS login
136 Logging in to :pserver:anoncvs@keithp.com:2401/local/src/CVS
137 CVS password: <hit return>
138 $ cvs -d :pserver:anoncvs@keithp.com:/local/src/CVS co waterfall
139 $ cd waterfall
140 $ xmkmf -a
141 $ make
142 # make install
143 # make install.man
144
145 Again, please make sure you are running an up-to-date freetype, and
146 that you are only examining integer sizes.
147
148 Reporting Problems
149 ==================
150
151 Please send problem reports to fonts at gnome org, with the following
152 information:
153
154 1. Version of Freetype, Xft2 and fontconfig
155 2. Whether TT hinting is being used, or the autohinter
156 3. Application being used
157 4. Character/Unicode code point that has problems (if applicable)
158 5. Version of which operating system
159 6. Please include a screenshot, when possible.
160
161 Please check the fonts list archives before reporting problems to cut
162 down on duplication.