readme.1st

智能画图软件

 To install from sources:
 ========================

 Installation instructions are found in the file INSTALL in this
 directory after going through this file. In a very small nutshell:

 - Under Unix, use configure and make
 
 - Under DOS, if you are using bash and DJGPP,
   you can just run config/djconfig.sh

 - Other platforms, copy the relevant makefile from config/
   to src, cd to src and make. See config/README for what
   each of those files is for.  Note: some of those files
   haven't been updated in ages, so they may no longer be
   usable.


 An important about the PDFlib Lite library:
 ===========================================

 The 'pdf' terminal driver uses an external library provided by 
 PDFlib GmbH, Germany ( http://www.pdflib.de/ ).  This library
 is available under two strictly separate licencing models.
 Depending on the environment you use gnuplot in, you may have to
 purchase a commercial licence for PDFlib even though gnuplot itself
 is free software.  

 There's a special version of PDFlib, called ``PDFlib Lite'', which
 is freely redistrutable, but programs linked to that are strictly for
 non-commercial usage only.  *You* are liable for whatever violations
 of this licence occur in a gnuplot binary built by you.


 IMPORTANT NOTE ON GIF, PNG and JPEG SUPPORT
 ===========================================

 Previous versions of gnuplot (through 3.7.1) used the gd library
 from http://www.boutell.com/gd/ to create GIF output. 
 Because of patent concerns (see Note 1 below) GIF support was removed
 from the gd library, and hence current versions of the gd library
 cannot be used to make GIF images.  This means that gnuplot, when
 linked against a current gd library, cannot produce GIF images either.

 On the other hand, the gd library now supports PNG and JPEG 
 image generation.  It also supports the use TrueType fonts,
 line widths, and other features that were not possible in the 
 older gnuplot terminal drivers for either GIF or PNG.

 When you build gnuplot 4.0 you may choose between two options.
 
 Option 1:
 If you link against an old version of the Boutell gd library 
 (versions 1.2 - 1.4) then you can enable the GIF terminal driver. 
 In this case you cannot enable either PNG or JPEG support via
 the gd library. You can still selection the old minimalistic
 PNG driver by using ./configure --with-png .

 Option 2:
 If you link against gd library version 1.8 or newer then you 
 get PNG and JPEG support.  In this case you cannot enable 
 the generation of true GIF images.  For backwards compatibility 
 with existing scripts, however, you can enable the 
 --with-gif=png option. This will use the old GIF driver, 
 accepting all the old 'set term gif' commands, but will actually 
 produce a PNG image file.  By default gnuplot assumes that if you
 have one of these newer versions of the gd library that it supports
 the use of TrueType fonts via the freetype library.  If you need to
 specify where this library lives, use --with-freetype=PATH.  If your
 local installation of libgd was not built with TrueType font support
 you can fall back to using generic fonts by using --with-freetype=no.

 Several open source programs exist that will convert PNG images 
 to GIF images. See Note 2 below.  If you need GIF images but want 
 to use the newer, more feature-full, terminal drivers, then you 
 may produce PNG images and convert them to GIF externally.  
 On platforms that allow pipes in the "set output" command, you can
 generate and convert the images at the same time, as in this example:

 	set terminal png medium
	set output '| convert png:- image.gif'


 Note 1 - UNISYS patent (why no more GIF images)
 -----------------------------------------------
 The UNISYS patent covers the LZW technology which is used to create
 gifs. To my knowledge, only gd library version 1.3, and possibly
 version 1.4 are free of LZW code and should therefore be used with
 gnuplot.  Versions 1.2 and 1.5 should not be used unless you have a 
 license from Unisys to use LZW code or are in a country where the
 UNISYS patent does not apply.

 Note 2 - Open source programs for PNG to GIF conversion
 -------------------------------------------------------

 ImageMagick ( www.ImageMagick.org ) 
 This is an open source package for general image manipulation and file 
 conversion, supported on a wide variety of platforms.  For example the 
 command "convert file.png file.gif" will convert a PNG image file to an 
 equivalent GIF image file.

 Utah Raster Toolkit ( http://www.cs.utah.edu/gdc/projects/urt/ )
 A general image file conversion library and associated file conversion
 utilities. Distributed as C source code. 
 To convert from PNG to GIF, use the commands
        pngtorle -o temp.rle image.png
        rletogif -o image.gif temp.rle