gimp/INSTALL.in

---------------------------------------
Installation instructions for GIMP @GIMP_APP_VERSION@
---------------------------------------

There are some basic steps to building and installing GIMP.

GIMP @GIMP_APP_VERSION@ replaces earlier GIMP 2.x versions. It is advised that you
uninstall them before installing GIMP @GIMP_APP_VERSION@. If you want to keep your
older GIMP 2.x installation in parallel to GIMP @GIMP_APP_VERSION@, you have to
choose a separate prefix which is not in your default library search
path.

GIMP @GIMP_APP_VERSION@ is fully backward compatible to all earlier GIMP 2.x version.
Plug-ins and scripts written for GIMP 2.8, 2.6 or earlier GIMP 2.x
versions will continue to work and don't need to be changed nor
recompiled to be used with GIMP @GIMP_APP_VERSION@.

The most important part is to make sure the requirements for a build
are fulfilled.  We depend on a number of tools and libraries which are
listed below. For libraries this means you need to also have the
header files installed.


  ******************************************************************
  * Unless you are experienced with building software from source, *
  * you should not attempt to build all these libraries yourself!  *
  * We suggest that you check if your distributor has development  *
  * packages of them and use these instead.                        *
  ******************************************************************


  1. You need to have installed a recent version of pkg-config (>= @GIMP_PKGCONFIG_VERSION@) available
     from https://www.freedesktop.org/software/pkgconfig/.

  2. You need gettext version 0.19.8 or newer. Older versions did not have support yet
     for certain file formats.

  3. You need to have GEGL version @GEGL_REQUIRED_VERSION@ or newer and babl version
     @BABL_REQUIRED_VERSION@ or newer. You can get them from https://gegl.org/ or clone
     them from the GNOME git repository:

       https://gitlab.gnome.org/GNOME/babl.git
       https://gitlab.gnome.org/GNOME/gegl.git

     GEGL must be built with Cairo support, i.e. -Dcairo=enabled option (required
     for some mandatory operations such as "gegl:npd").

     Introspection must be enabled for both babl and GEGL with
     -Denable-gir=true and -Dintrospection=true respectively. The only
     case where we don't build GIR data is when cross-compiling on meson
     because of the difficulty to make cross-tools for GObject
     Introspection. Nevertheless if you have working GIR cross-tools,
     you can force the expected behaviour with GIMP's meson option
     -Dcan-crosscompile-gir=true

     Optional:

     - build GEGL with libumfpack (SuiteSparse) (`-Dumfpack=enabled`)
       for alternative Matting engine "gegl:matting-levin" and OpenEXR
       library (`-Dopenexr=enabled`) for OpenEXR format support.
     - build GEGL with maxflow (https://github.com/gerddie/maxflow) and
       the option -Dworkshop=true in order to be able to select the
       experimental Paint Select tool in the Playground (operation
       "gegl:paint-select" is needed).
     - The "Show Image Graph" item in the "Debug" menu (hidden by
       default on stable release) requires the GEGL operation
       "gegl:introspect" which is always built but deactivated unless
       the `dot` tool from graphviz is available (runtime dependency).

  4. You need to have installed GTK+ version @GTK_REQUIRED_VERSION@ or newer.
     GIMP also needs a recent version of GLib (>= @GLIB_REQUIRED_VERSION@), GDK-Pixbuf
     (>= @GDK_PIXBUF_REQUIRED_VERSION@), and Pango (>= @PANGOCAIRO_REQUIRED_VERSION@). Sources for these can be grabbed
     from ftp://ftp.gtk.org/.

  5. We use cairo >= @CAIRO_REQUIRED_VERSION@, which is hosted at
     https://www.cairographics.org/.

  6. We require PangoCairo, a Pango backend using Cairo. Make sure you
     have Cairo, FreeType2 and fontconfig installed before you compile
     Pango. GIMP depends on freetype2 being newer than version @FREETYPE2_REQUIRED_VERSION@
     and fontconfig @FONTCONFIG_REQUIRED_VERSION@ or newer. Older versions are known to have
     bugs that seriously affect the stability of GIMP.

     On Windows, we recommend fontconfig 2.13.95 (or over) where support
     of fonts in user directory (Windows 1809 feature) appeared.

     We also require HarfBuzz @HARFBUZZ_REQUIRED_VERSION@ or newer, an
     OpenType text shaping tool. As this is a dependency for Pango, you
     will likely have it installed, but you may have to install a
     development package for the headers.

  7. The file-compressor plug-in requires zlib, libbzip2, and liblzma to
     be installed. All these libraries are required dependencies.

  8. For metadata access GIMP requires the gexiv2 @GEXIV2_REQUIRED_VERSION@ or newer library.
     It is hosted at: https://wiki.gnome.org/Projects/gexiv2

  9. libpng, libjpeg, libtiff, librsvg and lcms are hard dependencies
     that can not be disabled.

     There might be some issues with librsvg, based on the fact newer
     versions are in Rust which is not buildable on all platforms. Yet
     SVG support was deemed too important to be considered "optional"
     for a decent graphics activity. Nevertheless a packager really
     intent to have GIMP running on an architecture with no Rust support
     could still:

     1) easily patch out the file-svg plug-in from build system;
     2) build GIMP with --disable-vector-icons. Ironically librsvg is
     needed at build time for this option, in order to create PNG
     variants of icons (making librsvg unneeded at runtime). So all it
     takes is to have a build machine with librsvg to create the PNG
     icons, package and deliver them for machines without librsvg.

     This is the compromise we came with, i.e. officially making SVG a
     first-class file format, yet explaining how you could ignore it if
     you really wanted or needed to.

 10. For MyPaint brushes, brushlib (libmypaint) @LIBMYPAINT_REQUIRED_VERSION@ is used.
     The libmypaint repository is hosted at:

        https://github.com/mypaint/libmypaint

     If installing from repository, do not install the master branch!
     Checkout the last tag "v1.y.z" from `libmypaint-v1` branch instead
     (for instance "v1.6.1" tag at time of writing), or simply install
     from a tarball or from your favorite package manager.

     In particular, do NOT install tags or release tarballs versioned
     "v2.y.z". GIMP depends on the version 1 of libmypaint and is
     incompatible with the version 2 (which is still experimental anyway
     and has no stable release at time of writing).

 11. We also need the mypaint-brushes data package:

        https://github.com/mypaint/mypaint-brushes

     If installing from repository, install from branch "v1.3.x" or the
     last tag "v1.y.z" (e.g. "v1.3.1" at time of writing).
     In particular do NOT install from `master` branch which installs
     brushes incompatible with GIMP (the `master` branch brushes are
     targeted to libmypaint upcoming v2, not v1).

     Also this is a data packages and therefore it will install the
     pkg-config file inside `$PREFIX/share/pkgconfig/`. If you install
     mypaint-brushes from repository in a non-standard prefix, you will
     have to make sure your $PKG_CONFIG_PATH environment variable also
     lists `$PREFIX/share/pkgconfig/`.

 12. GIMP uses GLib's GIO library to handle file URIs and any I/O in
     general, transparently, regardless where the file is stored, i.e.
     locally, remotely, with which scheme, and so on. GIO in turn
     supports various backends through modules. We don't know all the
     modules available but since HTTP and HTTPS are so pervasive
     nowadays, we kind of consider a least GIO modules for these schemes
     mandatory (it allows to open from a pasted URL or just drag'n drop
     from e.g. a browser).

     For HTTP support (and many other schemes), on Linux at least, you
     should install `gvfs`:

        https://wiki.gnome.org/Projects/gvfs

     It is unclear whether `gvfs` can be built and installed on other
     platforms such as Windows and macOS.

     For HTTPS support, you should install `glib-networking`:

        https://gitlab.gnome.org/GNOME/glib-networking

     Of course there might be more modules providing support of more
     storage backends. Ideally GIMP would have support to load from any
     backend so packaging together with more GIO modules or recommending
     them in a package manager would be ideal. In any case, installing
     the ones for HTTP and HTTPS seems like the minimum nowadays.

 13. You may want to install other third party libraries or programs
     that are needed for some of the available plug-ins. We recommend
     to check that the following libraries are installed: openjpeg,
     webkit, libmng, libwmf, libaa and libgs (Ghostscript).

 14. HEIF support depends on the libheif library. If you don't have
     access to pre-built packages, the code is available at:

        https://github.com/strukturag/libheif

     Make sure you build libheif with libde265 and libx265 support (for
     respectively decoding and encoding of HEVC, i.e. HEIC files), and
     libaom decoder and encoder (for AV1, i.e. AVIF files), otherwise
     the plug-in is mostly useless.

 15. GObject Introspection requires the following dependencies to be
     built and installed with introspection as well: babl, cairo,
     GdkPixbuf, GEGL, GIO, GLib, GObject and GTK+.

 16. Windows builds can now generate backtrace logs upon a crash.
     The logs will be available in: %APPDATA%\GIMP\@GIMP_APP_VERSION@\CrashLog\
     The feature depends on Dr.MinGW's ExcHndl library:

        https://github.com/jrfonseca/drmingw

 17. Configure GIMP by running the `configure' script. You may want
     to pass some options to it, see below.

     Note that for Windows and macOS, we now recommend officially to
     build GIMP with `meson` instead of `autotools` (`configure` script,
     make, etc.). Therefore further build instructions below must be
     converted as their meson command equivalents. On all other
     platforms, the autotools are still recommended and more complete.

 18. Build GIMP by running `make'. The use of GNU make is recommended.
     If you need to tweak the build to make it work with other flavours
     of make, we'd appreciate if you'd send us a patch with the changes.

 19. Install GIMP by running `make install'. In order to avoid clashes
     with other versions of GIMP, we install a binary called gimp-@GIMP_APP_VERSION@.
     By default there's also a link created so that you can type 'gimp'
     to start gimp-@GIMP_APP_VERSION@.

 20. Summary of required packages and what version you need:

     Package Name         Version

     appstream-glib       @APPSTREAM_GLIB_REQUIRED_VERSION@
     ATK                  @ATK_REQUIRED_VERSION@
     babl                 @BABL_REQUIRED_VERSION@
     cairo                @CAIRO_REQUIRED_VERSION@
     Fontconfig           @FONTCONFIG_REQUIRED_VERSION@
     freetype2            @FREETYPE2_REQUIRED_VERSION@
     GDK-PixBuf           @GDK_PIXBUF_REQUIRED_VERSION@
     GEGL                 @GEGL_REQUIRED_VERSION@
     gexiv2               @GEXIV2_REQUIRED_VERSION@
     GIO
     GLib                 @GLIB_REQUIRED_VERSION@
     glib-networking
     GTK+                 @GTK_REQUIRED_VERSION@
     gvfs (on Linux)
     HarfBuzz             @HARFBUZZ_REQUIRED_VERSION@
     libbzip2
     libjpeg
     liblzma              @LIBLZMA_REQUIRED_VERSION@
     libmypaint           @LIBMYPAINT_REQUIRED_VERSION@
     libpng               @LIBPNG_REQUIRED_VERSION@
     libpoppler-glib      @POPPLER_REQUIRED_VERSION@
     librsvg              @RSVG_REQUIRED_VERSION@
     libtiff              @LIBTIFF_REQUIRED_VERSION@
     Little CMS           @LCMS_REQUIRED_VERSION@
     mypaint-brushes-1.0
     pangocairo           @PANGOCAIRO_REQUIRED_VERSION@
     poppler-data         @POPPLER_DATA_REQUIRED_VERSION@
     zlib

 21. Summary of optional packages:

     Package Name        Version        Feature

     cairo-pdf           @CAIRO_PDF_REQUIRED_VERSION@         PDF export
     ExcHndl             -              Crash logs on Windows with Dr. MinGW
     gs                  -              ghostscript
     libaa               -              ASCII art
     libheif             @LIBHEIF_REQUIRED_VERSION@          HEIF
     libmng              -              MNG
     libwebp             @WEBP_REQUIRED_VERSION@          WebP (built with --enable-libwebpmux and --enable-libwebpdemux)
     libwmf              @WMF_REQUIRED_VERSION@          WMF
     libXcursor          -              X11 Mouse Cursor
     libxpm              -              XPM
     openexr             @OPENEXR_REQUIRED_VERSION@          OpenEXR
     OpenJPEG            @OPENJPEG_REQUIRED_VERSION@          JPEG 2000
     webkit              @WEBKITGTK_REQUIRED_VERSION@         Help browser & webpage
     vala                -              Vala plug-ins

 22. Summary of optional runtime dependencies:

     darktable >= 1.7, with lua support enabled for raw loading
     RawTherapee >= 5.2 for raw loading
     xdg-email for sending emails
     sendmail for sending emails if --with-sendmail enabled
     gdb or lldb for our new bug-reporting dialog
     "gegl:matting-levin" GEGL operation for alternative matting engine
     Python @PYTHON3_REQUIRED_VERSION@ and PyGObject for Python 3 plug-ins
     GJS for Javascript plug-ins
     LuaJIT and LGI for Lua plug-ins
     dot for "Show Image Graph" (unstable branches)
     xdg-desktop-portal implemented for your desktop for various D-Bus API (screenshot, color-picking…)



Generic instructions for configuring and compiling auto-configured
packages are included below. Here is an illustration of commands that
might be used to build and install GIMP. The actual configuration,
compilation and installation output is not shown.

  % tar xvfz gimp-@GIMP_VERSION@.tar.gz   # unpack the sources
  % cd gimp-@GIMP_VERSION@                # change to the toplevel directory
  % ./configure                   # run the `configure' script
  % make                          # build GIMP
  % make install                  # install GIMP


Note: if building from repository (not tarballs), you may notice a meson
build system is also available in the repository. It is not the main
build system and is not recommended for stable packages other than on
macOS and Windows, as it still has several known issues, including
missing or broken features.
Yet we invite contributors to use the meson build if they wish to help
with debugging.

The `configure' script examines your system, and adapts GIMP to run on
it. The script has many options, some of which are described in the
generic instructions included at the end of this file. All of the
options can be listed using the command `./configure --help'. There
are several special options the GIMP `configure' script recognizes.
These are:

  --disable-vector-icons.  This option installs raster icons instead of
     vector icons.

  --enable-relocatable-bundle.  This option forces GIMP to search some
     resources (e.g. MyPaint brushes or libwmf fonts) relatively to the
     running prefix, rather than using build-time paths.

  --enable-shared and --disable-shared.  This option affects whether
     shared libraries will be built or not. Shared libraries provide
     for much smaller executables. The default is to enable shared
     libraries. Disabling shared libraries is almost never a good idea.

  --enable-debug and --disable-debug.  This option causes the build
     process to compile with debugging enabled. If debugging is
     disabled, GIMP will instead be compiled with optimizations turned
     on. The default is for debugging to be disabled. NOTE: This
     option is intended primarily as a convenience for developers.

  --enable-profile and --disable-profile. This option causes the build
     process to compile with execution profiling enabled. The default is
     for profiling to be disabled. NOTE: This option is intended primarily
     as a convenience for developers.

  --enable-ansi and --disable-ansi.  This option causes stricter
     ANSI C checking to be performed when compiling with GCC. The
     default is for strict checking to be disabled. NOTE: This option
     is intended primarily as a convenience for developers.

  --with-gimpdir=DIR.  This option changes the default directory
     GIMP uses to search for its configuration files from
     ~/.config/GIMP/@GIMP_APP_VERSION@ (the directory .config/GIMP/@GIMP_APP_VERSION@
     in the user's home directory) to ~/.config/DIR/@GIMP_APP_VERSION@.
     If DIR is an absolute path, the directory will be changed to DIR.

  --with-shm=[none|sysv|posix|auto].  This option allows you to specify
     how image data is transported between the core and plug-ins. Usually
     the best way to do this is detected automatically.

  --without-aa.  The AA plug-in needs libaa and configure checks for
     its presence. Use --without-aa if you run into problems.

  --without-libxpm.  The XPM plug-in needs libxpm and configure checks
     for its presence. If for some reason you don't want to build the
     XPM plug-in even though the library is installed, use
     --without-libxpm to disable it explicitly.

  --without-libmng.  The MNG plug-in needs libmng and configure checks
     for its presence. If for some reason you don't want to build the
     MNG plug-in even though the library is installed, use
     --without-libmng to disable it explicitly.

  --without-wmf.  The WMF plug-in needs libwmf2 and configure checks for
     its presence. Use --without-wmf if you run into problems.

  --without-webkit.  If for some reason you don't want to build the
     Help Browser plug-in, you can use --without-webkit to disable
     it explicitly.

  --without-print.  If for some reason you don't want to build the Print
     plug-in based on the GtkPrint API, you can build with --without-print.

  --without-alsa.  If you don't want to compile ALSA support into the
     MIDI input controller module, you can use the --without-alsa option.

  --without-linux-input.  If you don't want to compile the Linux Input
     controller module, you can use the --without-linux-input option.

  --without-hal.  If you want to build the Linux Input controller module
     without HAL support, you can use the --without-hal option.

  --without-mac-twain.  If you don't want to compile the Mac OS X
    TWAIN plug-in, you can use the --without-mac-twain option.

  --with-gif-compression=[lzw|rle|none].  Allows to tune the compression
     algorithm used by the GIF plug-in. If you are afraid of Unisys' LZW
     patent (which should have expired in most countries by now), you
     can go for simple run-length encoding or even configure the plug-in
     to create uncompressed GIFs.

  --enable-gtk-doc.  This option controls whether the libgimp API
     references will be created using gtk-doc. The HTML pages are
     included in a standard tarball, so you will only need this if you
     are building from SVN.

  --with-html-dir=PATH.  This option allows to specify where the
     libgimp API reference should be installed. You might want to modify
     the path so it points to the place where glib and gtk+ installed
     their API references so that the libgimp reference can link to
     them.

  --disable-mp. This option allows you to disable support for multiple
     processors. It is enabled by default.

  --with-sendmail[=PATH]. This option is used to tell GIMP to send email
     through sendmail instead of xdg-email. You can optionally indicate
     where to find the sendmail command. Otherwise sendmail will simply
     be searched in your $PATH at runtime.

  --with-desktop-dir=[PATH]. This option specifies where to install
     desktop files. These files are used by desktop environments that
     comply to the specs published at freedesktop.org. The default
     value ${prefix}/share should be fine if your desktop environment
     is installed in the same prefix as gimp. No files are installed
     if you call configure with --without-desktop-dir.

  --disable-default-binary. Use this option if you don't want to make
     gimp-@GIMP_APP_VERSION@ the default GIMP installation. Otherwise a link called
     gimp pointing to the gimp-@GIMP_APP_VERSION@ executable will be installed.

  --disable-gimp-console.  Use this option if you don't want the
     gimp-console binary to be built in addition to the standard binary.
     gimp-console is useful for command-line batch mode or as a server.

  --without-python.  If for some reason you don't want to install the
     Python plug-ins, you can use --with-python=no. Oppositely you can
     force the installations even without Python or PyGObject installed
     by setting --with-python=force (these are runtime dependencies
     which you can install later).

  --without-javascript.  If for some reason you don't want to install the
     JavaScript plug-ins, you can use --with-javascript=no. Oppositely
     you can force the installations even without GJS installed by
     setting --with-javascript=force (GJS is a runtime dependency which
     you can install later).

  --without-lua.  If for some reason you don't want to install the
     Lua plug-ins, you can use --with-lua=no. Oppositely you can force
     the installations even without LuaJIT or LGI installed by setting
     --with-lua=force (these are runtime dependencies which you can
     install later).

  --without-vala.  If for some reason you don't want to build the Vala
     plug-ins, you can use --without-vala.

  --without-script-fu.  If for some reason you don't want to build the
     Script-Fu plug-in, you can use --without-script-fu.

  --without-xmc.  The X11 Mouse Cursor(XMC) plug-in needs libXcursor
     and configure checks for its presence. If for some reason you
     don't want to build the XMC plug-in even though the library is
     installed, use --without-xmc to disable it explicitly.


The `make' command builds several things:
 - A bunch of public libraries in the directories starting with 'libgimp'.
 - The plug-in programs in the 'plug-ins' directory.
 - Some modules in the 'modules' subdirectory.
 - The main GIMP program 'gimp-@GIMP_APP_VERSION@' in `app'.

The `make install' commands installs the GIMP header files associated
with the libgimp libraries, the plug-ins, some data files and the GIMP
executable. After running `make install' and assuming the build process
was successful you should be able to run `gimp'.


When ./configure fails
======================

'configure' uses pkg-config, a tool that replaces the old foo-config
scripts. The most recent version is available from
	https://www.freedesktop.org/software/pkgconfig/

'configure' tries to compile and run a short GTK+ program. There are
several reasons why this might fail:

* pkg-config could not find the file 'gtk+-2.0.pc' that gets installed
  with GTK. (This file is used to get information about where GTK+ is
  installed.)

  Fix: Either make sure that this file is in the path where pkg-config
  looks for it (try 'pkg-config --debug' or add the location of
  gtk+-2.0.pc to the environment variable PKG_CONFIG_PATH before running
  configure.

* Libraries you installed are not found when you attempt to start GIMP.
  The details of how to fix this problem will depend on the system:

  On Linux and other systems using ELF libraries, add the directory to
  holding the library to /etc/ld.so.conf or to the environment variable
  LD_LIBRARY_PATH, and run 'ldconfig'.

  On other systems, it may be necessary to encode this path
  into the executable, by setting the LDFLAGS environment variable
  before running configure. For example:

    LDFLAGS="-R/home/joe/lib" ./configure
  or
    LDFLAGS="-Wl,-rpath -Wl,/home/joe/lib" ./configure

* An old version of the GTK+ libraries was found instead of
  your newly installed version. This commonly happens if a
  binary package of GTK+ was previously installed on your system,
  and you later compiled GTK+ from source.

  Fix: Remove the old libraries and include files.  If you are afraid
  that removing the old libraries may break other packages supplied by
  your distributor, you can try installing GLib, GTK+ and other
  libraries in a different prefix after setting the environment
  variable PKG_CONFIG_LIBDIR to point to lib/pkgconfig/ in that new
  prefix so that it does not try to read the *.pc files from the
  default directory (/usr/lib/pkgconfig).  However, removing the old
  packages is often the easier solution.

A detailed log of the ./configure output is written to the file
config.log. This may help diagnose problems.


When ./configure fails on plug-ins
==================================

There are some GIMP plug-ins that need additional third-party libraries
installed on your system. For example to compile the plug-ins that load
and save JPEG, PNG or TIFF files you need the related libraries and header
files installed, otherwise you'll get a message that plug-in xyz will not
be built.

If you are sure that those libraries are correctly installed, but configure
fails to detect them, the following might help:

Set your LDFLAGS environment variable to look for the library in a certain
place, e.g. if you are working in a bash shell you would say:
      export LDFLAGS="-L<path_to_library> -L<path_to_another_one>"
before you run configure.

Set your CPPFLAGS environment variable to look for the header file in a
certain place, e.g. if you are working in a bash shell you would say:
      export CPPFLAGS="-I<path_to_header_file> -I<path_to_another_one>"
before you run configure.


      Generic Instructions for Building Auto-Configured Packages
      ==========================================================


To compile this package:

1.  Configure the package for your system.  In the directory that this
file is in, type `./configure'.  If you're using `csh' on an old
version of System V, you might need to type `sh configure' instead to
prevent `csh' from trying to execute `configure' itself.

The `configure' shell script attempts to guess correct values for
various system-dependent variables used during compilation, and
creates the Makefile(s) (one in each subdirectory of the source
directory).  In some packages it creates a C header file containing
system-dependent definitions.  It also creates a file `config.status'
that you can run in the future to recreate the current configuration.
Running `configure' takes a minute or two.

To compile the package in a different directory from the one
containing the source code, you must use GNU make.  `cd' to the
directory where you want the object files and executables to go and
run `configure' with the option `--srcdir=DIR', where DIR is the
directory that contains the source code.  Using this option is
actually unnecessary if the source code is in the parent directory of
the one in which you are compiling; `configure' automatically checks
for the source code in `..' if it does not find it in the current
directory.

By default, `make install' will install the package's files in
/usr/local/bin, /usr/local/lib, /usr/local/man, etc.  You can specify
an installation prefix other than /usr/local by giving `configure' the
option `--prefix=PATH'.

You can specify separate installation prefixes for machine-specific
files and machine-independent files.  If you give `configure' the
option `--exec-prefix=PATH', the package will use PATH as the prefix
for installing programs and libraries.  Normally, all files are
installed using the same prefix.

`configure' ignores any other arguments that you give it.

If your system requires unusual options for compilation or linking
that `configure' doesn't know about, you can give `configure' initial
values for some variables by setting them in the environment.  In
Bourne-compatible shells, you can do that on the command line like
this:
        CC='gcc -traditional' DEFS=-D_POSIX_SOURCE ./configure

The `make' variables that you might want to override with environment
variables when running `configure' are:

(For these variables, any value given in the environment overrides the
value that `configure' would choose:)
CC              C compiler program.
                Default is `cc', or `gcc' if `gcc' is in your PATH.
INSTALL         Program to use to install files.
                Default is `install' if you have it, `cp' otherwise.
INCLUDEDIR      Directory for `configure' to search for include files.
                Default is /usr/include.

(For these variables, any value given in the environment is added to
the value that `configure' chooses:)
DEFS            Configuration options, in the form '-Dfoo -Dbar ...'
LIBS            Libraries to link with, in the form '-lfoo -lbar ...'

If you need to do unusual things to compile the package, we encourage
you to teach `configure' how to do them and mail the diffs to the
address given in the README so we can include them in the next
release.

2.  Type `make' to compile the package.

3.  Type `make install' to install programs, data files, and
documentation.

4.  You can remove the program binaries and object files from the
source directory by typing `make clean'.  To also remove the
Makefile(s), the header file containing system-dependent definitions
(if the package uses one), and `config.status' (all the files that
`configure' created), type `make distclean'.

The file `configure.ac' is used as a template to create `configure' by
a program called `autoconf'.  You will only need it if you want to
regenerate `configure' using a newer version of `autoconf'.

More autotools commands
=======================

GIMP uses the autotools build system which follows the GNU coding
standards. In particular all usual standard targets are obviously
supported (e.g. `make uninstall` for uninstalling) as well as common
variables and options, cross-compilation host and target, etc.

If you wish to know more, please refer to GNU documentation:
https://www.gnu.org/prep/standards/html_node/Managing-Releases.html