index.html

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

<P><A NAME="whatsnew1.6.2"><H3>What's new in version 1.6.2?</H3></A>
Version 1.6.2 from John Ellson <[e-mail]> adds two new functions:
<ul>
<li>gdImageStringTTF - scalable, rotatable, anti-aliased, TrueType strings using
the FreeType library, but only if libttf is found by configure.
<strong>We do not provide TrueType fonts. Obtaining them
is entirely up to you.</strong>
<li>gdImageColorResolve - an efficient alternative for the
common code fragment:
<pre>

      if ((color=gdImageColorExact(im,R,G,B)) < 0)
          if ((color=gdImageColorAllocate(im,R,G,B)) < 0)
              color=gdImageColorClosest(im,R,G,B);
</pre>
</ul>
<p>
Also in this release the build process has been converted to
GNU autoconf/automake/libtool conventions so that both (or either)
static and shared libraries can be built.
<P><A NAME="whatsnew1.6.1"><H3>What's new in version 1.6.1?</H3></A>
Version 1.6.1 incorporates superior PNG reading and writing code
from Greg Roelofs, with minor modifications by Tom Boutell. 
Specifically, I altered his code to read non-palette images
(converting them to palette images badly, by dithering them),
and to tolerate palette images with types of transparency that
gd doesn't actually support (it just ignores the advanced
transparency features). Any bugs in this area are therefore my 
fault, not Greg's.
<p>
Unlike gd 1.6, users should have no trouble linking with
gd 1.6.1 if they follow the instructions and install all of
the pieces. However, <strong>If you get undefined symbol errors,
be sure to check for older versions of libpng in your
library directories!</strong>
<P><A NAME="whatsnew1.6"><H3>What's new in version 1.6?</H3></A>
Version 1.6 features the following changes:
<p>
<strong>Support for 8-bit palette PNG images has been added.
Support for GIF has been removed.</strong> This step was taken
to completely avoid the legal controversy regarding the LZW
compression algorithm used in GIF. Unisys holds a patent which
is relevant to LZW compression. PNG is a superior image format
in any case. Now that PNG is supported by both Microsoft
Internet Explorer and Netscape (in their recent releases),
we highly recommend that GD users upgrade in order to get 
well-compressed images in a format which is legally unemcumbered.

<P><A NAME="whatsnew1.5"><H3>What's new in version 1.5?</H3></A>

Version 1.5 featured the following changes:

<dl>
<dt><b>New GD2 format</b>
<dd>      An improvement over the GD format, the GD2 format uses the zlib
          compression library to compress the image in chunks. This results
          in file sizes comparable to GIFs, with the ability to access parts
          of large images without having to read the entire image into memory.
<p>
  This format also supports version numbers and rudimentary validity
  checks, so it should be more 'supportable' than the previous GD format.
<p>
<dt><b>Re-arranged source files</b>
<dd>      gd.c has been broken into constituant parts: io, gif, gd, gd2 and
          graphics functions are now in separate files.
<p>
<dt><b>Extended I/O capabilities.</b>
<dd>      The source/sink feature has been extended to support GD2 file formats (which
          require seek/tell functions; seek must return 1 for success, 0 for failure), and to allow more general non-file I/O.
<p>
<dt><b>Better support for Lincoln Stein's Perl Module</b>
<dd>      The new gdImage*Ptr function returns the chosen format stored in a block of memory.
          This can be directly used by the GD perl module.
<p>
<dt><b>Added functions</b>
<dd>gdImageCreateFromGd2Part - allows retrieval of part of an image (good for huge images, like maps),
<br>gdImagePaletteCopy - Copies a palette from one image to another, doing it's best to match the colors in the target image to the colors in the source palette.
<br>gdImageGd2, gdImageCreateFromGd2 - Support for new format
<br>gdImageCopyMerge - Merges two images (useful to highlight part of an image)
<br>gdImageCopyMergeGray - Similar to gdImageCopyMerge, but tries to preserve source image hue.
<br>gdImagePngPtr, gdImageJpegPtr, gdImageWBMPPtr, gdImageGdPtr, gdImageGd2Ptr - return memory blocks for each type of image.
<br>gdImageCreateFromPngCtx, gdImageCreateFromGdCtx, gdImageCreateFromGd2Ctx, gdImageCreateFromGd2PartCtx - Support for new I/O context.

</dl>

<b>NOTE:</b> In fairness to Thomas Boutell, any bug/problems with any of the above features should
probably be reported to <a href=mailto:[e-mail]>Philip Warner</a>.

<P><A NAME="whatsnew1.4"><H3>What's new in version 1.4?</H3></A>

Version 1.4 features the following changes:
<dl>
<dt>Fixed polygon fill routine (again)
<dd>Thanks to Kirsten Schulz, version 1.4 is able to fill
numerous types of polygons that caused problems with
previous releases, including version 1.3.
<dt>Support for alternate data sources
<dd>Programmers who wish to load a GIF from something other
than a stdio FILE * stream can use the new
<a href="#gdImageCreateFromPngSource">gdImageCreateFromPngSource</a> function.
<dt>Support for alternate data destinations
<dd>Programmers who wish to write a GIF to something other
than a stdio FILE * stream can use the new
<a href="#gdImagePngToSink">gdImagePngToSink</a> function.
<dt>More tolerant when reading GIFs
<dd>
Version 1.4 does not crash when reading certain animated GIFs,
although it still only reads the first frame. Version 1.4 also has
overflow testing code to prevent crashes when reading
damaged GIFs.
</dl>
<P><A NAME="whatsnew1.3"><H3>What's new in version 1.3?</H3></A>
Version 1.3 features the following changes:
<dl>
<dt>Non-LZW-based GIF compression code
<dd>
Version 1.3 contained GIF compression code that uses simple Run Length
Encoding instead of LZW compression, while still retaining compatibility
with normal LZW-based GIF decoders (your browser will still like your GIFs).
<strong>LZW compression is patented by Unisys. We are currently reevaluating
the approach taken by gd 1.3. The current release of gd does not support
this approach. We recommend that you use the current release, and generate
PNG images.</strong> Thanks to 
Hutchison Avenue Software Corporation for contributing
the RLE GIF code.
<dt>8-bit fonts, and 8-bit font support
<dd>This improves support for European languages. Thanks are due
to Honza Pazdziora <[e-mail]> and also to
Jan Pazdziora <[e-mail]>. Also see the provided bdftogd
Perl script if you wish to convert fixed-width X11 fonts
to gd fonts.
<dt>16-bit font support (no fonts provided)
<dd>Although no such fonts are provided in the distribution,
fonts containing more than 256 characters should work if the
gdImageString16 and gdImageStringUp16 routines are used.
<dt>Improvements to the "webpng" example/utility
<dd>The "webpng" utility is now a slightly more useful application. Thanks to
Brian Dowling for this code.
<dt>Corrections to the color resolution field of GIF output
<dd>Thanks to Bruno Aureli.
<dt>Fixed polygon fills
<dd>A one-line patch for the infamous polygon fill bug, courtesy
of Jim Mason. I believe this fix is sufficient. However, if you
find a situation where polygon fills still fail to behave properly,
please send code that demonstrates the problem, <em>and</em> a fix if
you have one. Verifying the fix is important.
<dt>Row-major, not column-major
<dd>Internally, gd now represents the array of pixels as
an array of rows of pixels, rather than an array of columns
of pixels. This improves the performance of compression and
decompression routines slightly, because horizontally adjacent
pixels are now next to each other in memory. <strong>This should
not affect properly written gd applications, but applications that
directly manipulate the <code>pixels</code> array will require
changes.</strong>
</dl>
<A NAME="required"><H3>What else do I need to use gd?</H3></A>
<P>
To use gd, you will need an ANSI C compiler. <strong>All popular
Windows 95 and NT C compilers are ANSI C compliant.</strong> Any
full-ANSI-standard C compiler should be adequate. <strong>The cc
compiler released with SunOS 4.1.3 is not an ANSI C compiler.
Most Unix users who do not already have gcc should get it.
gcc is free, ANSI compliant and a de facto industry standard.
Ask your ISP why it is missing.</strong>
<P>
As of version 1.6, you also need the zlib compression library,
and the libpng library. As of version 1.6.2, you can draw text
using antialiased TrueType fonts if you also have the libttf
library installed, but this is not mandatory.
zlib is available for a variety of platforms from
<a href="http://www.freesoftware.com/pub/infozip/index.html">the zlib web site</a>.
libpng is available for a variety of platforms from
<a href="http://www.cdrom.com/pub/png/">the PNG web site</a>.

<P>
You will also want a PNG viewer, if you do not already have
one for your system, since you will need a good way to check the
results of your work. Netscape 4.04 and higher, and Microsoft
Internet Explorer 4.0 or higher, both support PNG.
<strong>Not every PNG-compatible viewer supports alpha channel
transparency,</strong> which is why gd 2.0.2 and above do alpha
blending in the library by default; it is possible to turn on the
saving of alpha channel information to the file instead.
<P>
<A NAME="getgd"><H3>How do I get gd?</H3></A>
<h4>Binaries (DLL for Windows programmers):</h4>
<ul>
<li><a href="http://www.boutell.com/gd/http/gdwin32.zip">.ZIP File of DLL, Headers, Et Cetera</a>
<p>
</ul>
<h4>Source Code:</h4>
<ul>
<li><a href="http://www.boutell.com/gd/http/gd-2.0.33.tar.gz">Gzipped Tar File (Unix)</a>
<li><a href="http://www.boutell.com/gd/http/gd-2.0.33.zip">.ZIP File of SOURCE CODE (Windows)</a>
</ul>
<P>
<A NAME="buildgd"><H3>How do I build gd?</H3></A>
<blockquote>
Win32 DLL users: if you are using MSVC, use the provided batch file
<code>makemsvcimport.bat</code> to make a bgd.lib import library
corresponding to the provided bgd.dll. Copy bgd.dll to your
application directory, or to your Windows sytem directory. In the
settings of your MSVC project, you <b>MUST</b> choose the
"multithreaded DLL" library option under "code generation." 
mingw32 and cygwin users can simply link with the provided libbgd.a 
stub library in order to use the DLL.
</blockquote>
Building gd From the Source
<p>
In order to build gd, you must first unpack the archive you have
downloaded. If you are not familiar with <code>tar</code> and
<code>gunzip</code> (Unix) or <code>ZIP</code> (Windows), please
consult with an experienced user of your system. Sorry, we cannot
answer questions about basic Internet skills.
<p>
Unpacking the archive will produce a directory called "gd-2.0.33".
<p>
<h4>For Unix</h4>
<code>cd</code> to the 2.0.33 directory and type:
<p>
<code>./configure</code>
<P>
<blockquote>
<STRONG>NOTE: BY DEFAULT, THE LIBRARY IS INSTALLED IN 
<code>/usr/local/lib</code></strong> and the include files are
installed in <code>/usr/local/include</code>. IF YOU ARE
UPGRADING, you may wish to use:
<pre>
./configure --prefix=/usr
</pre>
Rather than just <code>./configure</code>, before typing
<code>make</code> and <code>make install</code>.
</blockquote>
<p>
If all goes well, this will create a Makefile. If all does not go well --
for instance, if neither the the JPEG nor the PNG and ZLIB libraries
are found -- you will need to install those libraries, then come back
and run <code>configure</code> again. 
<p>
If necessary, make changes to the resulting Makefile. Then, 
type "make". If there are no errors, follow this with "make install". 
Because gd 2.0 and above installs as a shared library, it is necessary to 
install the library properly before running gd-based programs.
<p>
If you get errors, type <code>./configure --help</code> for more
information about the available options. In the unlikely event
that the GNU autoconf-produced configure script does not work well
for you, you may wish to try <code>configure.pl</code>, a
simple Perl script with similar but less complete capabilities.
If all else fails, try renaming <code>makefile.sample</code>
to <code>Makefile</code>. However, <code>./configure</code> is
almost always your best bet.
<blockquote>
<h4>For Windows</h4>
Use the DLL version! See the paragraph at the beginning of this sectino.
If you really want to compile it yourself for some strange reason, read on.
<p>
Create a project using your favorite programming environment.
Copy all of the gd files to the project directory. Add <code>gd.c</code>
to your project. Add other source files as appropriate. Learning the
basic skills of creating projects with your chosen C environment
is up to you. Alternatively, use the free <code>mingw32</code> 
or <c