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

McNabb.
<li>Paul den Dulk found a degenerate case that crashes
gdImageToPalette. Fixed.
<li>Optimization by Ilia Chipitsine to avoid wasting time with
offscreen scanlines during polygon rasterization.
<li>Optimized PNG saving by Phong Tran. Speeds up saves a 
little bit. 
<li>Bug in gdImageCopyResized fixed by Mao Morimoto.
</ul>
<P>
<A NAME="whatsnew2.0.15"><H3>What's new in version 2.0.15?</H3></A>
<P>
<ul>
<li>gd.c in 2.0.14 contained an instance of declaring variables
after the first line of executable code appears. This is of course
not allowed by ANSI C, although many compilers accept it. 
My apologies. Thanks to Jeff Vendetti for reporting this quickly.
</ul>
<P>
<A NAME="whatsnew2.0.14"><H3>What's new in version 2.0.14?</H3></A>
<P>
<ul>
<li>2.0.13 was available for mere minutes due to a typo
in the new bounds-checking code for antialiased line drawing. Fixed.
<li>Not all platforms -- notably msys/mingw -- have an ssize_t type.
We now call an int an int in gd_jpeg.c, with good results. 
(Note: ssize_t is signed, unlike size_t, and it needs to be here.)
</ul>
<P>
<A NAME="whatsnew2.0.13"><H3>What's new in version 2.0.13?</H3></A>
<P>
<ul>
<li>The <code>main()</code> function of one of the test programs
was accidentally included in the gd shared library, causing problems
on some platforms. This has been corrected. Thanks to many people
who pointed this out.
<li>The antialiased drawing functions now have proper bounds
checking. Thanks to Arne Jorgensen.
<li>A void function returned a value in gd_png.c, causing warnings
and, on some platforms, compilation errors but no reported runtime problems.
Thanks to Kevin Smith, among others.
<li>Autohinting was being forced ON for freetype text output. This is
apparently meant only for testing freetype and does not look as good
as the default behavior (FT_LOAD_DEFAULT). Thanks to Bob Ostermann.
<li>penf.x is properly reset when newlines are encountered in freetype
text output. Thanks to Christopher J. Grayce.
</ul>
<P>
<A NAME="whatsnew2.0.12"><H3>What's new in version 2.0.12?</H3></A>
<P>
<ul>
<li>Small but numerous code cleanups by Dr. Martin Zinser.
<li><a href="#gdImageSetClip">gdImageSetClip</a> and
<a href="#gdImageGetClip">gdImageGetClip</a> have been added. All
drawing routines now stay within the specified clipping rectangle.
Note that the <a href="#gdImageBoundsSafe">gdImageBoundsSafe</a> function
now returns true only if the specified location is within the
clipping rectangle. Of course, the default clipping area is the 
entire image. The behavior of existing gd applications does not change.
<li>Support for fast drawing of antialiased lines and polygons,
by Bright Fulton and Frank Faubert. To learn more about this feature,
read about the <a href="#gdImageSetAntiAliased">gdImageSetAntiAliased</a> 
function, which is used to set the foreground color for antialiasing,
as well as the <a href="#gdAntiAliased">gdAntiAliased</a> constant, which
is passed to line- and polygon-drawing functions in place of a color.
This code does not currently support an alpha channel component in the
specified foreground color, or in the existing background image, 
but <em>does</em> perform alpha blending against an opaque background.
Also see the 
<a href="#gdImageSetAntiAliasedDontBlend">gdImageSetAntiAliasedDontBlend</a> 
function, which allows the specification of a special background
color that should never be blended with the foreground.
<li>Fixes to color mapping in <a href="#gdImageCopyMergeGray">gdImageCopyMergeGray</a>. Thanks to Philip Warner.
<li><a href="#gdImageStringFTEx">gdImageStringFTEx</a> now supports
explicit specification of the desired character mapping.
This is useful when a font offers more than one of Unicode,
Shift_JIS, and Big5. 
<li>The PNG compression level can now be specified when writing PNG
images. See the new <a href="#gdImagePngEx">gdImagePngEx</a>,
<a href="#gdImagePngEx">gdImagePngEx</a>,
<a href="#gdImagePngCtxEx">gdImagePngCtxEx</a>, and
<a href="#gdImagePngPtrEx">gdImagePngPtrEx</a> functions.
<li>The annotate utility builds without error in the absence of
freetype, although of course it is not useful without freetype.
<li>Thorben Kundinger fixed a bug relating to the use of palette-based
images as brushes when drawing on truecolor images.
<li>Michael Schwartz corrected a problem with his code for drawing
thick lines.
<li>Prior to 2.0.12, any alpha channel component in the
<em>destination</em> image was ignored when drawing with
alpha blending in effect (see 
<a href="#gdImageAlphaBlending">gdImageAlphaBlending</a>). 2.0.12
correctly preserves an appropriate proportion of the alpha component
of the destination, just as it preserves an appropriate proportion
of the red, green and blue components, depending on the opacity
of the foreground. Thanks to Frank Warmerdam for pointing out the issue.
<li>Memory leaks on failed attempts to load fonts
in <a href="#gdImageStringFTEx">gdImageStringFTEx</a> were corrected.
Thanks to Frank Faubert.
<li>The impact of kerning is now correctly included in the calculation
of the bounding box returned by the freetype text routines. This issue
was pointed out by several individuals.
<li>Color problems with the <code>gd2</code> file format routines
were fixed by Steven Brown. These problems were due to the
incorrect use of a signed integer.
<li>Version 2.0.12 supports the <code>gd</code> file format correctly
for truecolor images. Truecolor <code>gd</code> files created with
earlier releases in the 2.0 series must be written again. The <code>gd</code>
file format is used to quickly load an entire uncompressed image, typically 
an existing background to which additional material will be added; it is not a 
general purpose file format. More advanced capabilities are also available
via the <code>gd2</code> format. Thanks to Andreas Pfaller for reporting 
the problem. 
<li>Signed vs. unsigned problem caused misbehavior when attempting to
load a bad JPEG image. Thanks to Geert Jansen.
<li>Existing truecolor PNG images with simple single-color transparency are 
now loaded properly, thanks to Slaven Rezic.
<li>The <a href="#gdImageTrueColorToPalette">gdImageTrueColorToPalette</a>
function no longer attempts to preserve an alpha channel in the original.
My attempt to do so resulted in significantly inferior output even if no
alpha channel was present in the original. Thanks to Barend Gehrels for
submitting a new adaptation of Tom Lane's jquant2.c which does a very
high-quality job of palette conversion. Thanks also to Steven Brown, who
submitted patches allowing a single 100% transparent color in the
original truecolor image to be preserved. In practice, more complex 
alpha channels in palettes are ill-supported and difficult to 
allocate skillfully.
</ul>
<P>
<A NAME="whatsnew2.0.11"><H3>What's new in version 2.0.11?</H3></A>
<P>
<ul>
<li>Support for the "gd2" file format, which allows fast loading of all or
only part of an existing image, has been properly debugged for use with
truecolor images. (Palette images already worked properly, except for a
bug when loading from a regular file with gdImageCreateFromGd2Part, which
has also been fixed.) .gd2 files can be either compressed or uncompressed,
and they allow useful tricks such as fast loading of a 500x500 pixel
region of a 6000x3000 pixel image, without uncompressing <em>all</em> of the
image. .gd2 is NOT a general purpose file format and should only be used
where quick loading of a background image or subset of a larger image
is required. For more information, see
<a href="#gdImageGd2">gdImageGd2</a>, 
<a href="#gdImageCreateFromGd2">gdImageCreateFromGd2</a>,
and 
<a href="#gdImageCreateFromGd2Part">gdImageCreateFromGd2Part</a>.
<li>The gd2topng utility has been extended to support extraction of
only part of an image from a .gd2 file. This is both a demonstration and 
a practical tool.
<li>Additional <code>configure</code> improvements by Lars Hecking.
</ul>
<P>
<A NAME="whatsnew2.0.10"><H3>What's new in version 2.0.10?</H3></A>
<P>
<ul>
<li>gdImageLine now clips to the edges of the image before drawing
lines, which greatly improves performance when many lines extend
outside or are entirely outside the actual image. Thanks to 
Nick Atty for this code.
<li>gdImageBoundsSafe is replaced with a macro when called internally;
this improves the performance of gdImageSetPixel and gdImageGetPixel
a little bit, and therefore everything else as well. Thanks to
Nicky Atty for the idea.
<li>Transparent indexes are handled properly with non-truecolor
source images in gdImageCopy. Thanks to Frank Warmerdam.
<li>floor() replaced with a cast to long in gdImageCopyResampled,
for a roughly 35% performance boost. Thanks to John Buckman.
<li>gdft.c builds correctly on WIN32 without patches.
<li>Much faster gdImageCreateFromJpeg routines, thanks to Christian
Aberger for more efficient pointer arithmetic.
<li>gdtestft correctly builds without PNG tests if PNG support is not present.
Thanks to Gabriele Verzeletti.
</ul>
<P>
<A NAME="whatsnew2.0.9"><H3>What's new in version 2.0.9?</H3></A>
<P>
<ul>
<li>Version 2.0.9 contains a fix to gdImageCopyResized which allows
correct results when copying a palette-based image with a single
transparent index into a truecolor image. Thanks to Thorben
Kundinger.
<li>More <code>configure</code> fixes from Lars Hecking. Thanks, Lars. 
</ul>
<P>
<A NAME="whatsnew2.0.8"><H3>What's new in version 2.0.8?</H3></A>
<P>
<ul>
<li>Version 2.0.8 contains additional fixes to the 'configure' script,
allowing a clean out-of-the-box build on more systems.
<li>Version 2.0.8 adds the new 
<a href="#gdImageCopyRotated">gdImageCopyRotated</a> function, which
can rotate any rectangular image region by an arbitrary number of degrees.
</ul>
<P>
<A NAME="whatsnew2.0.7"><H3>What's new in version 2.0.7?</H3></A>
<P>
Version 2.0.7 corrects a problem which caused 'configure' to complain
that the directory NONE was not found, in various places, causing
the configuration process to stop. There are no code changes.
<P>
<A NAME="whatsnew2.0.6"><H3>What's new in version 2.0.6?</H3></A>
<P>
<ul>
<li>
Fixed a compilation problem with gdft.c. A declaration appeared
after executable code, and gcc let it slide by, so it made it
out the door. My apologies!
<li>As penance, I have seen to it that the entire library
now compiles cleanly with the <code>-Wall</code>, <code>-ansi</code>
and <code>-pedantic</code> options enabled.
</ul>
<p>
<A NAME="whatsnew2.0.5"><H3>What's new in version 2.0.5?</H3></A>
<ul>
<li>libgd 2.0.5 INSTALLS IN /usr/local/lib BY DEFAULT. IF YOU WANT
IT TO INSTALL IN /usr/lib, YOU MUST SPECIFY THIS at
<code>configure</code> time using this syntax:
<p>
<code>./configure --prefix=/usr</code> 
<li>gd now uses GNU autoconf. This means that the provided
<code>configure</code> script should be compatible with all standard
GNU configure options and will figure out the correct settings for a
much wider range of operating systems. Many, many thanks to
Lars Hecking for taking care of this.
<li>The <a href="#gdImageStringFTEx">gdImageStringFTEx</a> function
is now included, thanks to Wez Furlong. My apologies to Wez for the
unreasonable amount of time this patch has sat in my queue.
<li>Additional fixes from Wez Furlong.
<li>Arithmetic cleanup by Doug Claar.
<li>Corrections to loading and saving of alpha channel
information in PNG files, by Andrew Hull.
<li>gdImageTrueColorToPalette does not contain
unneeded test code.
<li>gdImageCopyResized works properly again when copying
from a non-truecolor source.
</ul>
<P>
<A NAME="whatsnew2.0.4"><H3>What's new in version 2.0.4?</H3></A>
The following contributions from John Ellson:
<ul>
<li>Various test programs now compile in the absence
of PNG support
<li>gdIOCtx correctly calls gdFree rather than free
<li>Various cleanups to pass -Wall without warnings
<li>Support for Adobe-style Type 1 fonts (.pfa and .pfb files)
via freetype
<li>gdImageColorResolve and gdImageColorResolveAlpha will not
attempt to resolve a color request to the transparent color index
(for palette-based images)
<li>Improved font search path support
<li>Antialiased freetype text on palette images works properly
when more than one image is created in a single program lifetime
with different color indexes
<li>Better threshold for two-color "mono" images 
<li>Memory leak fixes
<li>Text rotation fix
<li>More extensive default font path
<li>fontwheeltest and fontsizetest test programs for freetype
</ul>
And the following additional fixes:
<ul>
<li><code>configure</code> now correctly detects and provides
support for the Xpm library and its dependencies (Len Makin)
</ul>
<A NAME="whatsnew2.0.3"><H3>What's new in version 2.0.3?</H3></A>
<ul>
<li>The <code>configure</code> script has been extensively modified