Restructured and improved the documentation.

Most of the content of README.rst was moved to a separate
user manual, and to a build manual.

The README was simplified to provide just the most important
information.

The user manual was extensively reworked, and beautified with images.

README.rst

@@ -1,492 +1,86 @@
-Minetest Mapper C++
+Minetest Mapper
-===================
+###############
 
-A port of minetestmapper.py to C++ from https://github.com/minetest/minetest/tree/master/util
+A tool to generate maps of minetest and freeminer worlds.
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-Requirements
+Quick links (functional on github. Elsewhere possibly not):
-------------
 
-* libgd
+:All features:		`<doc/features.rst>`_
-* sqlite3 (enabled by default, set ENABLE_SQLITE3=0 in CMake to disable)
+:User manual:		`<doc/manual.rst>`_
-* leveldb (optional, set ENABLE_LEVELDB=1 in CMake to enable leveldb support)
+:Changelog:		`<Changelog>`_
-* hiredis (optional, set ENABLE_REDIS=1 in CMake to enable redis support)
+:Building:		`<doc/build-instructions.rst>`_
+:Github:		`<https://github.com/Rogier-5/minetest-mapper-cpp>`_
+:Bugs:			`<https://github.com/Rogier-5/minetest-mapper-cpp/issues>`_
 
-Compilation
+Features (short list)
------------
+=====================
+
+Map Generation
+--------------
+
+* Support for both minetest and freeminer worlds
+* Support for sqlite3, leveldb and redis map databases
+* Generate a subsection of the map, or a full map
+  (but note that the size of generated images is limited)
+* Generate regular maps or height-maps
+* All colors for regular or height maps are configurable
+* Draw player positions
+* Draw different geometric figures, or text on the map
+* Draw the map at a reduced scale. E.g. 1:4.
+* Draw a scale on the left and/or top side of the map,
+  and/or a height scale (for height maps) on the bottom.
+* Optionally draw some nodes transparently (e.g. water)
+* User Manual
+
+Building
+--------
+* Supports both the gcc and clang compiler suites
+* Build windows, rpm, deb and/or tar.gz installation
+  packages. Or simply type 'make install'.
+
+Quick Start
+===========
+
+After installation, minetestmapper is started as follows:
+
+('\\' is a continuation character - the command-line continues
+on the next line. Type return only after the line that does
+not end with the continuation character)
 
-Plain:
 
 ::
 
-    cmake .
+    minetestmapper \
-    make
+	--input <world-directory> \
+	--output <image-file-name.png>
 
-With levelDB and Redis support:
+If the world is not too large, and if minetestmapper is installed in
+a  system directory, it will most likely work as expected.
+
+Possibly, minetestmapper will not be able to find a colors.txt file. If that happens,
+the colors.txt file can be specified on the command-line:
 
 ::
 
-    cmake -DENABLE_LEVELDB=true -DENABLE_REDIS=true .
+    minetestmapper \
-    make
+	--input <world-directory> \
+	--output <image-file-name.png> \
+	--colors <filename>
 
-Create installation package(s):
+Or the colors.txt file must be installed in a location where minetestmapper will find it.
+A colors.txt file (named ``colors.txt``, in lowercase) in the world's directory will certainly
+be found. Depending on the system and the configuration, other locations are available. Use the
+following command to find out which:
 
 ::
 
-    cpack
+    minetestmapper \
+	--input <world-directory> \
+	--output <image-file-name.png> \
+	--verbose-search-colors=2
 
-Cmake variables:
+Manual
-^^^^^^^^^^^^^^^^
+======
 
-ENABLE_SQLITE3:
+For more elaborate usage instruction, please consult the user manual: `<doc/manual.rst>`_.
-    Enable sqlite3 backend support (on by default)
-
-ENABLE_LEVELDB:
-    Enable leveldb backend support (off by default)
-
-ENABLE_REDIS:
-    Enable redis backend support (off by default)
-
-ENABLE_ALL_DATABASES:
-    Enable support for all backends (off by default)
-
-CMAKE_BUILD_TYPE:
-    Type of build: 'Release' or 'Debug'. Defaults to 'Release'.
-
-CREATE_FLAT_PACKAGE:
-    Create a .tar.gz package suitable for installation in a user's private directory.
-    The archive will unpack into a single directory, with the mapper's files inside
-    (this is the default).
-
-    If off, .tar.gz, .deb and .rpm packages suitable for system-wide installation
-    will be created if possible. The tar.gz package will unpack into a directory hierarchy.
-
-    For creation of .deb and .rpm packages, CMAKE_INSTALL_PREFIX must be '/usr'.
-
-    For .deb package creation, dpkg and fakeroot are required.
-
-    For .rpm package creation, rpmbuild is required.
-
-ARCHIVE_PACKAGE_NAME:
-    Name of the .zip or .tar.gz package (without extension). This will also be
-    the name of the directory into which the archive unpacks.
-
-    Defaults to minetestmapper-<version>-<os-type>
-
-    The name of .deb and .rpm packages are *not* affected by this variable.
-
-Usage
------
-
-Binary `minetestmapper` has two mandatory paremeters, `-i` (input world path)
-and `-o` (output image path).
-
-::
-
-    ./minetestmapper -i ~/.minetest/worlds/my_world/ -o ~/map.png
-
-
-Parameters
-^^^^^^^^^^
-
-version:
-    Print version ID of minetestmapper.
-
-colors <file>:
-    Filename of the color definition file to use.
-
-    By default, a file 'colors.txt' is used, which may be located:
-
-    * In the directory of the world being mapped
-
-    * In the directory two levels up from the directory of the world being mapped,
-      provided that directory contains a file 'minetest.conf'
-
-    * In the user's private directory ($HOME/.minetest)
-
-    * In the system directory correpsonding to the location where minetestmapper
-      is installed. Usually, this would be /usr/share/games/minetestmapper/colors.txt
-      or /usr/local/share/games/minetestmapper/colors.txt
-
-    * For compatibility, in the current directory as a last resort.
-      This causes a warning message to be printed.
-
-    If the colors file contains duplicate entries for the same node,
-    one with alpha = 255, or absent, and one with alpha < 255, the former
-    is used without 'drawalpha', and the latter is used with 'drawalpha':
-
-::
-
-    # Entry that is used without 'drawalpha':
-    default:water-source	39 66 106
-    # Entry that is used with 'drawalpha':
-    default:water-source	78 132 212 64 224
-
-    The colors file can include other colors files using:
-
-::
-
-    @include filename
-
-    Any entries after the inclusion point override entries from the
-    included file. Already defined colors can be 'undefined' by specifying
-    '-' as color:
-
-::
-
-    default:stone		71 68 67
-    # default-colors.txt might override the color of default:stone
-    @include default-colors.txt
-    # color of default:dirt_with_grass from default-colors.txt is overridden:
-    default:dirt_with_grass	82 117 54
-    # Color of water is undefined here:
-    default:water_source	-
-    default:water_flowing	-
-
-heightmap[-grey]:
-    Draw a height-map instead of a regular map.
-
-    A height map needs a custom colors file that contains only the nodes that
-    define the height. As a general directive, plants and other special nodes
-    should not be included in the file. Normally, water nodes should not be
-    included either.
-
-    The colors used are predefined and not yet configurable.
-
-    The colors support a maximum depth below sea level of 60, although below a
-    depth of 30 they become progressively darker.
-    Above sea level, they support a maximum height of 250.
-    Starting from height level 70, greyish colors are used (think: 'rocky')
-    Starting from height level 111, shades of white are used (think: 'snowy').
-
-    For '--heightmap-grey', a 255-level greyscale map is generated, with colors
-    ranging from black for level 0 and below, to white for 255 and above.
-
-heightmap-scale
-    Scale the heights of the map before computing the colors.
-
-    Note that the water level is not rendered correctly for scale factors
-    smaller than 1, nor for small non-integer scale factors.
-
-sealevel:
-    Set the sea level for the height map. Nodes at or below sea level are
-    drawn in blue, nodes above sea level are drawn in other colors.
-
-    The sea level *does* *not* reflect the presence of actual water.
-
-bgcolor:
-    Background color of image, `--bgcolor #ffffff`
-
-blockcolor:
-    Default color of nodes in blocks that are in the database, `--blockcolor #ffffff`
-
-    If a block is in the database, but some of its nodes are not visible (because they are
-    air, or 'invalid', the nodes are drawn in this color (as opposed to the background
-    color, which shows for blocks that are not in the database)
-
-scalecolor:
-    Color of scale, `--scalecolor #000000`
-
-playercolor:
-    Color of player indicators, `--playercolor #ff0000`
-
-    An alpha value can be specified, but due to a bug in the
-    drawing library, it will not have the desired effect.
-
-origincolor:
-    Color of origin indicator, `--origincolor #ff0000`
-
-    An alpha value can be specified, but due to a bug in the
-    drawing library, it will not have the desired effect.
-
-drawscale:
-    Draw tick marks, `--drawscale`
-
-drawplayers:
-    Draw player indicators, `--drawplayers`
-
-draworigin:
-    Draw origin indicator, `--draworigin`
-
-drawalpha[=cumulative|cumulative-darken|average|none]:
-    Allow blocks to be drawn with transparency, `--drawalpha=average`
-
-    In cumulative mode, transparency decreases with depth, and darkness of
-    the color increases. After a certain number of transparent blocks
-    (e.g. water depth), the color will become opaque, and the underlying
-    colors will no longer shine through. The height differences *will*
-    still be visible though.
-
-    In cumulative-darken mode, after the color becomes opaque, it will gradually
-    be darkened to visually simulate the bigger thickness of transparent blocks.
-    The downside is that eventually, the color becomes black.
-
-    Cumulative-darken mode makes deeper, but not too deep water look much better.
-    Very deep water will become black though.
-
-    In average mode, all transparent colors are averaged. The blocks remain transparent
-    infinitely. If no parameter is given to --drawalpha, 'average' is the default.
-
-    'None' disables alpha drawing. This is the same as not using --drawalpha at all.
-
-    For backward compatibility, 'nodarken' is still recognised as alias for 'cumulative';
-    'darken' is still recognised as alias for 'cumulative-darken'. Please don't use
-    them, they may disappear in the future.
-
-    Note that each of the different modes has a different color definition
-    for transparent blocks that looks best. For instance, for water, the following
-    are suggested:
-
-    (disabled): 39 66 106 [192 224 - optional: alpha configuration will be ignored]
-
-    cumulative: 78 132 255 64 224
-
-    cumulative-darken: 78 132 255 64 224
-
-    average: 49 82 132 192 224 (look also good with alpha disabled)
-
-    Custom colors files are provided for these alternatives: colors-average-alpha.txt
-    and colors-cumulative-alpha.txt
-
-drawair:
-    Draw air blocks. `--drawair`
-
-    For best results, the air color should be defined as fully transparent
-    so that the color of underlying blocks overrides it.
-
-    This option has a significant performance impact.
-
-noshading:
-    Don't draw shading on nodes, `--noshading`
-
-min-y:
-    Don't draw nodes below this y value, `--min-y -25`
-
-max-y:
-    Don't draw nodes above this y value, `--max-y 75`
-
-backend:
-    Use specific map backend, supported: auto, sqlite3, leveldb, redis, `--backend leveldb`
-
-    By default, the backend is 'auto', i.e. it is determined from the backend
-    setting in the world's world.mt file (if found).
-
-centergeometry  <geometry>:
-    (see below, under 'geometry')
-
-cornergeometry  <geometry>:
-    (see below, under 'geometry')
-
-geometry <geometry>:
-    Limit the part of the world that is included in the map.
-
-    <geometry> has one of the formats:
-
-    <width>x<height>[<+|-xoffset><+|-yoffset>]	(dimensions & corner)
-
-    <xoffset>,<yoffset>+width+height		(corner & dimensions)
-
-    <xcenter>,<ycenter>:widthxheight		(center & dimensions)
-
-    <xcorner1>,<ycorner1>:<xcorner2>,<ycorner2>
-
-    The old/original format is also supported:
-
-    <xoffset>:<yoffset>+width+height		(corner & dimensions)
-
-    For 'cornergeometry', the offsets ([xy]offset or [xy]center) will
-    be at the lower-left corner of the image (offsets increase from left
-    to right, and from bottom to top).
-
-    For 'centergeometry', the offsets ([xy]offset or [xy]center) will be
-    in the center of the image.
-
-    For plain 'geometry', the offsets will be at the corner, or in
-    the center, depending on the geometry format.
-
-    If the offsets are not specified (with the first format),
-    the map is centered on the center of the world.
-
-    By default, the geometry has pixel granularity, and a map of
-    exactly the requested size is generated.
-
-    *Compatibility mode*:
-
-    If the *first* geometry-related option on the command-line
-    is `--geometry`, *and* if the old format is used, then for
-    compatibility, the old behavior is default instead (i.e.
-    block granularity, and a smaller map if possible). Block
-    granularity is also enabled when the obsolete (and otherwise
-    undocumented) option '--forcegeometry' is found first.
-
-    Examples:
-
-    `--geometry 10x10-5-5`
-
-    `--geometry 100,100:500,1000`
-
-    `--cornergeometry 50x50+100+100`
-
-    `--centergeometry 1100x1300+1000-500`
-
-    `--geometry 1100x1300`
-
-geometrymode pixel,block,fixed,shrink:
-    Specify how the geometry should be interpreted. One or
-    more of the flags may be used, separated by commas or
-    spaces. In case of conflicts, the last flag takes
-    precedence.
-
-    When using space as a separator, make sure to enclose
-    the list of flags in quotes!
-
-geometrymode pixel:
-    Interpret the geometry specification with pixel granularity,
-    as opposed to block granularity (see below).
-
-    A map of exactly the requested size is generated (after
-    adjustments due to the 'shrink' flag).
-
-geometrymode block:
-    Interpret the geometry specification with block granularity.
-
-    The requested geometry will be extended so that the map does
-    not contain partial map blocks (of 16x16 nodes each).
-    At *least* all pixels covered by the geometry will be in the
-    map, but there may be up to 15 more in every direction.
-
-geometrymode fixed:
-    Generate a map of the requested geometry, even if part
-    or all of it would be empty.
-
-    *NOTE*: If this flag is used, and no actual geometry is
-    specified, this would result in a maximum-size map (65536
-    x 65536), which is currently not possible, and will fail,
-    due to a bug in the drawing library.
-
-geometrymode shrink:
-    Generate a map of at most the requested geometry. Shrink
-    it to the smallest possible size that still includes the
-    same information.
-
-    Currently, shrinking is done with block granularity, and
-    based on which blocks are in the database. If the database
-    contains empty, or partially empty blocks, there may still
-    be empty pixels at the edges of the map.
-
-sqlite-cacheworldrow:
-    When using sqlite, read an entire world row at one, instead of reading
-    one block at a time.
-
-    This may improve performance when a large percentage of the world is mapped.
-
-chunksize:
-    Manually specify the chunk size (for use with --tiles chunk)
-
-tiles <tilesize>[+<border>]|block|chunk
-    Divide the map in square tiles of the requested size. A border of the
-    requested width (or width 1, of not specfied) is drawn between the tiles.
-    In order to preserve all map pixels (and to prevent overwriting them with
-    borders), extra pixel rows and columns for the borders are inserted into
-    the map.
-
-    The special values 'block' and 'chunk' draw tiles that correspond to map
-    blocks (16x16 nodes) or to chunks (the unit of map generation; 5x5 blocks
-    for a world with default settings).
-
-    In order to allow partial world maps to be combined into larger maps, edge
-    borders of the map are always drawn on the same side (left or top). Other
-    edges are always border-less.
-
-    Examples:
-
-    `--tiles 1000`
-
-    `--tiles 1000+2`
-
-    `--tiles block`
-
-    NOTE: As a consequence of preserving all map pixels:
-
-    * tiled maps (in particular slanted straight lines) may look slightly
-      skewed, due to the inserted borders.
-
-    * scale markers never align with tile borders, as the borders are
-      logically *between* pixels, so they have no actual coordinates.
-
-
-tileorigin x,y
-    Arrange the tiles so that one tile has its bottom-left (i.e. south-west)
-    corner at map coordinates x,y.
-
-    (see also `tilecenter`)
-
-tilecenter x,y|map|world
-    Arrange the tiles so that one tile has its center at map coordinates x,y.
-
-    If the value 'world' is used, arrange for one tile to have its center
-    at the center of the world instead. This is the default for tiles.
-
-    If the value 'map' is used, arrange for one tile to have its center
-    at the center of the map instead.
-
-    Examples:
-
-    `--tilecenter -500,-500`
-
-    `--tileorigin 0,0`
-
-    `--tilecenter map`
-
-    `--tilecenter world`
-
-tilebordercolor
-    Color of border between tiles, `--tilebordercolor #000000`
-
-draw[map]<figure> "<geometry> <color> [<text>]"
-    Draw a geometrical figure on the map, using either world or map
-    coordinates.
-
-    NOTE: the quotes around the two or three parameters to these
-    options are absolutely required.
-
-    Possible figures: point, line, circle, ellipse, rectangle, text;
-    'circle' is an alias for 'ellipse' - it therefore requires
-    two dimensions, just like an ellipse.
-
-    Examples:
-
-    `--drawellipse "5x5+2+3 #ff0000"`
-
-    `--drawcircle "4,5:5x4 #ff0000"`
-
-    `--drawline "5x5+8+8 #80ff0000"`
-
-    `--drawline "8,8:12,12 #80ff0000"`
-
-    `--drawmapline "3x5+4+6 #ffff0000"`
-
-    `--drawtext "0,0 #808080 center of the world"
-
-    `--drawmaptext "0,0 #808080 top left of the map"
-
-    Note that specifying an alpha value does not have the expected
-    result when drawing an ellipse.
-
-verbose:
-    report some useful / interesting information:
-
-    * maximum coordinates of the world
-
-    * world coordinates included the map being generated
-
-    * number of blocks: in the world, and in the map area.
-
-    Using `--verbose=2`, report some more statistics, including:
-
-    * database access statistics.
-
-verbose-search-colors:
-    report the location of the colors file(s) that are read.
-
-    With `--verbose-search-colors=2`, report all locations that are being
-    considered as well.

doc/build-instructions.rst

@@ -0,0 +1,129 @@
+Minetest Mapper Build Instructions
+##################################
+
+Minetestmapper can be built on posix (linux, freebsd, ...), osx and windows
+platforms (although not all platforms receive the same amount of testing -
+please let me know if there is a problem on your platform).
+
+Both the gcc and clang compiler suites are supported.
+
+Requirements
+============
+
+**Libraries:**
+
+* libgd
+* sqlite3 (enabled by default, set ENABLE_SQLITE3=0 in CMake to disable)
+* leveldb (optional, set ENABLE_LEVELDB=1 in CMake to enable leveldb support)
+* hiredis (optional, set ENABLE_REDIS=1 in CMake to enable redis support)
+
+**Build environment:**
+
+* C++ compiler suite (clang or gcc)
+* cmake
+* make
+
+**Documentation:**
+
+If converting the documentation to HTML, or another format is desired:
+
+* python-docutils
+
+
+Compilation
+===========
+
+Plain:
+
+::
+
+    cmake .
+    make
+
+With levelDB and Redis support:
+
+::
+
+    cmake -DENABLE_LEVELDB=true -DENABLE_REDIS=true .
+    make
+
+Create installation package(s):
+
+::
+
+    cpack
+
+Cmake variables:
+----------------
+
+ENABLE_SQLITE3:
+    Enable sqlite3 backend support (on by default)
+
+ENABLE_LEVELDB:
+    Enable leveldb backend support (off by default)
+
+ENABLE_REDIS:
+    Enable redis backend support (off by default)
+
+ENABLE_ALL_DATABASES:
+    Enable support for all backends (off by default)
+
+CMAKE_BUILD_TYPE:
+    Type of build: 'Release' or 'Debug'. Defaults to 'Release'.
+
+CREATE_FLAT_PACKAGE:
+    Create a .tar.gz package suitable for installation in a user's private directory.
+    The archive will unpack into a single directory, with the mapper's files inside
+    (this is the default).
+
+    If off, .tar.gz, .deb and .rpm packages suitable for system-wide installation
+    will be created if possible. The tar.gz package will unpack into a directory hierarchy.
+
+    For creation of .deb and .rpm packages, CMAKE_INSTALL_PREFIX must be '/usr'.
+
+    For .deb package creation, dpkg and fakeroot are required.
+
+    For .rpm package creation, rpmbuild is required.
+
+ARCHIVE_PACKAGE_NAME:
+    Name of the .zip or .tar.gz package (without extension). This will also be
+    the name of the directory into which the archive unpacks.
+
+    Defaults to minetestmapper-<version>-<os-type>
+
+    The names of .deb and .rpm packages are *not* affected by this variable.
+
+Converting the documentation
+============================
+
+Using python-docutils, the manual can be converted to a variety of formats.
+
+**HTML**
+
+Conversion to HTML yields a nice manual:
+
+::
+
+	cd doc
+	rst2html manual.rst > manual.html
+
+**Unix manpage**
+
+Conversion to unix man format has acceptable, but not perfect results:
+
+::
+
+	cd doc
+	rst2html manual.rst > minetestmapper.1
+
+**PDF**
+
+The results of using rst2pdf (which, as an aside, is not part of python-docutils)
+to convert to PDF directly are not good: random images are scaled down, some even
+to almost invisibly small. If PDF is desired, a good option is to open the HTML file
+in a webbrowser, and print it to PDF.
+
+**Other**
+
+Other conversions are possible using python-docutils. If you tried any, and
+they warrant specific instructions, feel free to contribute.

doc/features.rst

@@ -0,0 +1,107 @@
+Minetest Mapper Features
+########################
+
+Minetestmapper generates maps of minetest and freeminer worlds.
+
+Major Features
+==============
+* Support for both minetest and freeminer
+* Support for sqlite3, leveldb and redis map databases
+* Generate a subsection of the map, or a full map
+  (but the size of generated images is limited - see
+  'Known Problems' below)
+* Generate regular maps or height-maps
+* All colors for regular or height maps are configurable
+* Draw player positions
+* Draw different geometric figures, or text on the map
+* Draw the map at a reduced scale. E.g. 1:4.
+* Draw a scale on the left and/or top side of the map,
+  and/or a height scale (for height maps) on the bottom.
+* Optionally draw some nodes transparently (e.g. water)
+* User manual
+
+
+Build Features
+==============
+* Supports both the gcc and clang compiler suites
+* Build windows, rpm, deb and/or tar.gz installation
+  packages. Or simply type 'make install'.
+
+Minor Features
+==============
+* Specify a number colors symbolically ('red', ...)
+* Draw a grid on the map
+* Show a progress indicator
+* Draw shades to accentuate height differences (on by default)
+* Report actual world dimensions in all directions, as
+  well which part of it will be in the map.
+
+Differences From Stock Minetestmapper
+=====================================
+* Support for the new freeminer database format
+* Different methods for drawing transparent blocks
+  (more than transparency on and off)
+* Different colors can be specified for nodes, in the
+  same colors file, depending on whether transparency
+  is enabled or not.
+* Abiliy to draw different geometric figures, or text on the map
+* Map dimensions can be specified in different ways:
+
+  - using two corners
+  - using a corner and the size
+  - using the center and the size
+
+* Pixel or block granularity for the dimensions
+  (stock minetestmapper always uses block granularity: it rounds
+  all dimensions to the next multiple of 16).
+* Colors files are automatically searched for in the world
+  directory, or in system directories
+* Colors files can include others, so that just a few colors can
+  be redefined, and the system colors file used for the others.
+* The map can be draw at a reduced scale.
+  This means that a full world map can now be generated.
+* A grid can be drawn on the map.
+* A number of symbolic colors ('red', ...) are available on the
+  command-line.
+* The scale can be enabled on the left and top side individually
+* Major and minor (tick) intervals are configurable for the scale
+* Block numbers are shown on the scale as well
+
+In addition a number bugs have been fixed. As bugs are also getting
+fixed in the stock version of minetestmapper, no accurate list
+can be given.
+
+Known Problems
+==============
+
+* It is currently not possible to generate huge maps.
+
+  On 32-bit systems, the map size is limited by the maximum amount of memory
+  (or really: the size of the address space).
+  this means in practise that maps larger than about 24100x24100 (determined
+  experimentally - YMMV) can't be generated. Note, that even if a larger
+  /could/ be generated, most 32-bit applications would still not be able to
+  display it for the same reason.
+
+  On 64-bit systems, the libgd image library unfortunately limits the map
+  size to approximately 2147483648 pixels, e.g. approximately 46300x46300.
+
+  If a full map is required for a world that is too large, there are currently
+  two options:
+
+    - Generate the map in sections, and use another application to paste them
+      together.
+    - Generate a 1:2 or 1:4 scaled version of the map, if the reduced level of
+      detail is acceptable.
+
+  A third alternative, is of course to support the libgd project in removing
+  the current restrictions on image size.
+
+* On scaled maps, the colors of some pixels may be invisibly different on
+  different systems.
+
+  The difference would be at most 1/256 per color.
+  (e.g., a pixel with color ``#4c92a1`` on one system, might have color
+  ``#4x91a1`` on another system)
+
+  The cause of this difference has not been determined yet.