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Linux/Unix下的绘图函数库（Graphic Drawing Library）

to work properly in tests with both Solaris and Linux. Other platforms
should also work based on feedback received and integrated to date.
<li>The <code>--prefix</code> option to <code>configure</code>
works properly.
<li>The <code>annotate</code> utility has been added. This is a
very handy tool for adding freetype text to existing JPEGs. After
<code>make install</code>, type <code>annotate -h</code> for more 
information. Thanks to Joel Dubiner.
</ul>
<P>
<A NAME="whatsnew2.0.2"><H3>What's new in version 2.0.2?</H3></A>
<ul>
<li>A "configure" script has been added. After wrestling with GNU
autoconf for a while, I got tired of trying to make it detect libraries
but accept their absence gracefully, and so on. Instead, I wrote a short
Perl script which does the job and builds a reasonable Makefile. Those
who find it doesn't detect their system's needs properly are welcome
to contribute patches or the necessary commands.
<li>Antialiased freetype text output now works properly in both
truecolor and non-truecolor contexts! Hurrah! On a truecolor image
it is possible, for instance, to draw antialiased text on an arbitrarily
complex background with 50% alpha blending (transparency), and get the
expected pretty results. Thanks to Joel Dubiner for his support of this work.
<li><strong>By default, alpha blending is now done within the library.</strong>
Also, by default, alpha channel is not saved with PNG images. This means
that programmers who try loading a JPEG, scribbling some pretty antialiased
text on it, and saving the JPEG again will now get the results they
expected. It also means that, by default, users will not run afoul of
the fact that many web browsers don't properly support full PNG alpha
channel. 
<li>Various submitted bug fixes have been incorporated.
<li>Various other submitted changes have not been incorporated. Sorry.
The interval between 2.0.1 and 2.0.2 was simply too long, and changes
accumulated which were not mutually compatible. I'll do better in
the future, especially with bug fixes.
</ul> 
<P><A NAME="whatsnew2.0.1"><H3>What's new in version 2.0.1?</H3></A>
<ul>
<li>Workaround for a bug in gcc, apparently found in gcc 2.7.2 and up.
I reproduced and fixed it while using gcc 2.9.5.2. The bug occurred only
when the -g option was in use. This problem caused gcc to spew
internal error messages unrelated to the correctness of the code
in gd_gd2.c. Howard Jones was first to report it.
<li><a href="#gdImageFilledEllipse">gdImageFilledEllipse</a> documented
and altered; no longer requires a superfluous style argument. Thanks to
Francis James Franklin.
<li>The Makefile now offers the correct syntax for
optionally creating a static library. Thanks to Jean-Lous Regez,
among others.
<li>A nested comment, an attempt to return the value of a void function,
and a potentially significant error in gdImageCopyResampled were fixed
thanks to Joseph Shirley.
<li>A bug preventing proper truecolor text rendering was fixed,
thanks to Jason Gallagher.
<li><a href="#gdImageStringFT">gdImageStringFT</a> (FreeType) should 
now work better against a transparent or semitransparent background,
and should act in a manner consistent with the most recent
<a href="#gdImageAlphaBlending">gdImageAlphaBlending</a> setting.
Antialiasing is now done via the alpha channel mechanism if the
image is a truecolor image. 
<li>Bugs in the output of gdImageArc and gdImageFilledArc were reported
by Bruce Verderaime. A simple and correct but inefficient implementation
has been substituted until fixes are contributed for the faster code,
which is in gd_arc_f_buggy.c along with the test program that reproduces
the bug(s).
<li><a href="#gdImageFilledArc">gdImageFilledArc</a> now offers additional
style options, which can be combined to produce various effects.  
<li>Masahito Yamaga ([e-mail]) sent a patch to improve
support for Japanese output via <a href="#gdImageStringFT">gdImageStringFT</a>. 
He also added a new <code>readme.jpn</code> file.
<li>Zillions of documentation fixes.
</ul>
<P><A NAME="whatsnew2.0"><H3>What's new in version 2.0?</H3></A>
<ul>
<li><strong>Support for truecolor images!</strong> Version 2.0 can
load truecolor PNGs with no loss of color information, and almost
no loss of alpha channel information. Version 2.0 can also load
truecolor JPEGs with as little loss as possible; however, bear in
mind that JPEG is a lossy format, so repeated load/save cycles
always reduce image quality. This is not a bug. To create
a truecolor image from scratch, call the new
<a href="#gdImageCreateTrueColor">gdImageCreateTrueColor</a>
function. The <a href="#gdImageCreate">gdImageCreate</a> function
is still available to create palette images, and may also be
referred to as <a href="#gdImageCreatePalette">gdImageCreatePalette</a>.
<li><strong>Support for alpha channels!</strong> In addition to
24 bits of color information for each pixel (eight bits of
red, green, and blue respectively), version 2.0 supports
7 bits of "alpha channel" information. This is used to determine
exactly how transparent the pixel should be. There is also support
for a full 7 bits of transparency for each individual palette index
in a palette-based image. Please note that, as of this writing,
only Macintosh Internet Explorer 5.x and Mozilla/Netscape 6.x
display partial transparency properly.
<li>The new <a href="#gdImageAlphaBlending">gdImageAlphaBlending</a>
function allows for two different modes of drawing. In blending mode,
the alpha channel component of the color supplied to all drawing
functions, such as <a href="#gdImageSetPixel">gdImageSetPixel</a>,
determines how much of the underlying color should be allowed to
shine through. The resulting image is not transparent. In non-blending 
mode, drawing color is copied literally with the alpha channel 
information, resulting in a transparent image. Blending mode is
not available when drawing on palette images. 
<li>The <a href="#gdImageCopyResampled">gdImageCopyResampled</a>
function provides "smooth" copying from a large image to a smaller
one, using a weighted average of the pixels of the source area rather 
than selecting one representative pixel. This function is identical
to <a href="#gdImageCopyResized">gdImageCopyResized</a> when the
destination image is a palette image.
<li>The <a href="#gdImageTrueColorToPalette">gdImageTrueColorToPalette</a>
function converts a truecolor image to a palette image. The code for
this function was originally drawn from the Independent JPEG Group library
code, which is excellent. The code has been modified to preserve as much
alpha channel information as possible in the resulting palette, in addition 
to preserving colors as well as possible. This does not work as well as
might be hoped. It is usually best to simply produce a truecolor
output image instead, which guarantees the highest output quality.
<li>A very high degree of backwards compatibility with existing
gd 1.x code has been maintained, at both the source code and binary
level. <strong>Code which directly accesses the <code>pixels</code> array
will fail only if it encounters an existing truecolor image</strong>, which may
happen if the code attempts to open and modify an existing JPEG or 
truecolor PNG. Such code should be modified to check the
<code>trueColor</code> flag of the <code>gdImage</code> structure, and
refer to the <code>tpixels</code> array instead when it is set.
<li>gd is now compiled and installed as a shared library. However,
gd still does not use autoconf, because I (TBB) have very limited
patience with autoconf. These days, most Unix systems provide a fairly
POSIX-standard environment, and the provided Makefile is likely to work well
if users read it and follow the instructions at the top.
<li>Support for line thickness was added by Michael Schwartz. My apologies
to him for sitting on his patches for so long. See the new
<a href="#gdImageSetThickness">gdImageSetThickness</a> function, which
affects all standard gd functions that draw lines and curves. In addition,
Michael added a convenient <a href="#gdImageEllipse">gdImageEllipse</a>
function. 
<li>The new <a href="#gdImageFilledArc">gdImageFilledArc</a> function
provides a straightforward way to draw filled arcs. Also,
<a href="#gdImageFilledEllipse">gdImageFilledEllipse</a> is a 
convenient way to fill an ellipse without specifying starting
and ending angles. Thanks go out to F J Franklin.
<li>To put an end to the confusion, TrueType 1.x support has been
removed in favor of TrueType 2.x support. The old
gdImageStringTTF function simply invokes gdImageStringFT.
<li>The specialized .gd and .gd2 file formats have been upgraded to support
truecolor. New images written by the versions of these functions
found in 2.0 will be rejected, with varying degrees of grace, by
older versions of gd. THIS AFFECTS THE .GD and .GD2 FORMATS ONLY. IF YOU
ARE CONFUSED BY THIS PARAGRAPH, IT PROBABLY DOESN'T APPLY TO ANYTHING
YOU WILL EVER ENCOUNTER. Since these file formats are absolutely,
positively *not* designed for distributing images, just for
preprocessing them, this should not be a big problem. gd 2.0 should
read old .gd and .gd2 files correctly.
</ul>
<P><A NAME="whatsnew1.8.4"><H3>What's new in version 1.8.4?</H3></A>
<ul>
<li>Add support for FreeType2  (John Ellson  [e-mail])
<li>Add support for finding in fonts in a builtin DEFAULT_FONTPATH,
or in a path from the GDFONTPATH environment variable.
<li>remove some unused symbols to reduce compiler warnings
<li>bugfix in size comparisons in gdImageCompare
<li>REXX now mentioned
<li>All memory allocation functions are now wrapped within the
library; gdFree is exported and recommended for freeing memory
returned by the gdImage(Something)Ptr family of functions.
</ul>
<P><A NAME="whatsnew1.8.3"><H3>What's new in version 1.8.3?</H3></A>
<ul>
<li>WBMP output memory leak fixed
<li><code>#include &lt;gd.h&gt;</code> corrected to <code>#include "gd.h"</code> in gd_wbmp.c 
<li>Documented the fact that the source and output images shouldn't
match in the WBMP test except for black and white source images
</ul>
<P>
<A NAME="whatsnew1.8.2"><H3>What's new in version 1.8.2?</H3></A>
<ul>
<li>WBMP support debugged and improved by Johann Van den Brande
<li>WBMP tests added to gdtest.c by Thomas Boutell
<li>Use of platform-dependent 'install' command removed by Thomas Boutell
<li>Comments added to Makefile warning users to juggle the order of the
libraries if the linker complains; is there any portable way to do this
automatically, short of using autoconf?
<li>Documentation of <a href="#gdImageCreateFromXpm">gdImageCreateFromXpm</a>
corrected
<li>Updated links to fast-moving, always dodging libpng and zlib web sites
</ul>
<P><A NAME="whatsnew1.8.1"><H3>What's new in version 1.8.1?</H3></A>
<ul>
<li>Optional components no longer built by default (following the
documentation)
<li>JPEG code no longer requires inappropriate header files
<li>Win32 patches from Joe Gregorio
<li>16-bit font support for bdftogd, from Honza Pazdziora
</ul>
<P><A NAME="whatsnew1.8"><H3>What's new in version 1.8?</H3></A>
<ul>
<li>Support for JPEG output, courtesy of Doug Becker
<li>A link to Michael Bradbery's Pascal wrapper
<li>Support for WBMP output, courtesy of Maurice Szmurlo
<li>gdImageColorClosestHWB function based on hue, whiteness, blackness,
superior to the regular gdImageColorClosest function, courtesy 
of Philip Warner
<li>License clarification: yes, you can modify gd
</ul>
<h4>Additional JPEG Information</h4>
Support for reading and writing JPEG-format images is courtesy
of Doug Becker and the Independent JPEG Group / Thomas G. Lane.  You
can get the latest version of the IJG JPEG software from <A
HREF="ftp://ftp.uu.net/graphics/jpeg/">ftp://ftp.uu.net/graphics/jpeg/</A>
(e.g., the <A
HREF="ftp://ftp.uu.net/graphics/jpeg/jpegsrc.v6b.tar.gz">jpegsrc.v6b.tar.gz</A>
file).  You <strong>must</strong> use
version 6b or later of the IJG JPEG software.  You might also consult
the <A HREF="http://www.faqs.org/faqs/jpeg-faq/">JPEG FAQ</A> at
<A HREF="http://www.faqs.org/faqs/jpeg-faq/">http://www.faqs.org/faqs/jpeg-faq/</A>.
<P><A NAME="whatsnew1.7.3"><H3>What's new in version 1.7.3?</H3></A>
Another attempt at Makefile fixes to permit
linking with all libraries required on platforms with order-
dependent linkers. Perhaps it will work this time.
<P><A NAME="whatsnew1.7.2"><H3>What's new in version 1.7.2?</H3></A>
An uninitialized-pointer bug in <code>gdtestttf.c</code> was corrected.
This bug caused crashes at the end of each call to gdImageStringTTF on
some platforms. Thanks to Wolfgang Haefelinger.
<p>
Documentation fixes. Thanks to Dohn Arms.
<p>
Makefile fixes to permit
linking with all libraries required on platforms with order-
dependent linkers.
<P><A NAME="whatsnew1.7.1"><H3>What's new in version 1.7.1?</H3></A>
A minor buglet in the Makefile was corrected, as well as an inaccurate
error message in <code>gdtestttf.c</code>. Thanks to Masahito Yamaga.
<P><A NAME="whatsnew1.7"><H3>What's new in version 1.7?</H3></A>
Version 1.7 contains the following changes:
<ul>
<li>Japanese language support for the TrueType functions.
Thanks to Masahito Yamaga.
<li><code>autoconf</code> and <code>configure</code> have been removed, in favor of a 
carefully designed Makefile which produces and properly installs
the library and the binaries. System-dependent variables are
at the top of the Makefile for easy modification. I'm sorry, 
folks, but autoconf generated <strong>many, many confused email 
messages</strong> from people who didn't have things where autoconf 
expected to find them. I am not an autoconf/automake wizard, and 
gd is a simple, very compact library which does not need to 
be a shared library. I <strong>did</strong> make many improvements
over the old gd 1.3 Makefile, which were directly inspired by the 
autoconf version found in the 1.6 series (thanks to John Ellson).
<li>Completely ANSI C compliant, according to the <code>-pedantic-errors</code>
flag of gcc. Several pieces of not-quite-ANSI-C code were causing problems
for those with non-gcc compilers.
<li><code>gdttf.c</code> patched to allow the use of Windows symbol
fonts, when present (thanks to Joseph Peppin). 
<li><code>extern "C"</code> wrappers added to <code>gd.h</code> and the
font header files for the convenience of C++ programmers. 
<code>bdftogd</code> was also modified to automatically insert these
wrappers into future font header files. Thanks to John Lindal.
<li>Compiles correctly on platforms that don't define <code>SEEK_SET</code>.
Thanks to Robert Bonomi.
<li>Loads Xpm images via the 
<a href="#gdImageCreateFromXpm"><code>gdImageCreateFromXpm</code></a>
function, if the Xpm library is available. Thanks to Caolan McNamara.
</ul>
<P><A NAME="whatsnew1.6.3"><H3>What's new in version 1.6.3?</H3></A>
Version 1.6.3 corrects a memory leak in gd_png.c. This leak caused
a significant amount of memory to be allocated and not freed when
writing a PNG image.