MapServer6.4.1教程学习--标注地图(1-4)

示例1.4
标注地图
(http://www.mapserver.org/tutorial/example1-4.html#example1-4)
我们也可以给地图添加标注：



MapServer具有非常灵活的标注引擎。它支持truetype字体的同时也支持本地图片方式。还支持TrueType字体的缩放。标注角度和位置能够用户定制。如果你花时间去学习创建好标注的那些参数，你会得到信息量丰富且令人愉悦的地图作为奖励。
下面是示例1.4的mapfile:
#The annotated map file (sort of)
#Created by Pericles S. Nacionales for the MapServer tutorial
#20050408
#
#MapServer map file uses the pound sign (#) to denote the start of a line
#comment--each line that needs to be commented has to be prepended with a"#".
#
#Map files begin with MAP keyword to signify the start of the map object.
#Well, the entire map file is THE map object. Enclosed between MAP and END
#at the very bottom of this map file, are keyword/value pairs and other
#objects.
MAP
  IMAGETYPE     PNG
  EXTENT        -97.238976 41.619778 -82.122902 49.385620
  SIZE          400 300
  SHAPEPATH     "../data"
  IMAGECOLOR    255 255 255
  FONTSET       "../fonts/fonts.list"
 
  # Layer objects are defined beneath the mapobject.  You need at least one
  # layer defined in your map file before youcan display a map...  You can
  # define as many layers as you'd likealthough a limit is typically hard-coded
  # in map.h in the MapServer source.  The default limit is set at 100.  You'd
  # have to have a very specialized applicationto need more than 100 layers in
  # your application.
 
  # Start of LAYER DEFINITIONS---------------------------------------------
  LAYER # States polygon layer begins here
    NAME        states_poly
    DATA        states_ugl
    STATUS      OFF
    TYPE        POLYGON
 
    # CLASSITEM defines the non-spatialattribute that you will be using to
    # separate a layer into classes.  This attribute will be in the DBF file
    # of your shapefile (it will be differentfor each data format).  In this
    # example the shapefile states_ugl has anassociated database
    # (states_ugl.dbf) that contains anattribute called "CLASS".  Youwill be
    # using two values in the CLASS attributeto separate the classes (also
    # called themes) used in this layer--landand water.  CLASSITEM is used in
    # association with the EXPRESSION parameterin the CLASS object.  See below.
    CLASSITEM   "CLASS"
 
    # Just like CLASSITEM, LABELITEM definesthe database attribute that you
    # will be using to draw labels.  In this case, the values of the attribute
    # "STATE" will be used to labelthe states polygons.
    LABELITEM   "STATE"
 
    # The class object is defined within thelayer object.  You can define as
    # many classes as you need (well, there arelimits as with layers, but it's
    # senseless to define more than ten on a"normal" layer.  There are
    # situations, however, where you might haveto do it.)
    CLASS
      NAME 'States'
      EXPRESSION 'land'
 
      # There are styles in a class, just likethere are classes in a layer,
      # just like there are layers in amap.  You can define multiple styles in
      # a class just as you can define multipleclasses in a layer and multiple
      # layers in a map.
      STYLE
        COLOR      232 232 232
      END
 
      # There can be labels in a class, justlike there are classes in a layer,
      # just like there are layers in amap.  You can define multiple labels in
      # a class just as you can define multipleclasses in a layer and multiple
      # layers in a map.
      # MapServer has a very flexible labelingsystem.  With that flexibility
      # comes complexity, specially when usingtruetype fonts.  Please read
      # through the LABEL section of theMapServer map file documentation at
      # http://www.mapserver.org/mapfile formore information.
      LABEL
        COLOR 132 31 31
        TYPE TRUETYPE
        FONT arial-bold
        SIZE 12
        ANTIALIAS TRUE
        POSITION CL
        PARTIALS FALSE
        MINDISTANCE 300
        BUFFER 4
        # create a background shadow
        # Note that the tutorial package has not been updated, so this has
        # to be done manually!
        #SHADOWCOLOR 218 218 218  # prior to version 6
        #SHADOWSIZE 2 2  # prior to version 6
        STYLE   # since to version 6
          GEOMTRANSFORM 'labelpoly'
          COLOR 218 218 218
          OFFSET 2 2
        END # STYLE
      END # end of label
    END
 
    CLASS
      NAME 'Water'
      EXPRESSION 'water'
 
      STYLE
        COLOR      198 198 255
      END
    END
  END # States polygon layer ends here
 <
4000
/p>
  LAYER # States line layer begins here
    NAME        states_line
    DATA        states_ugl
    STATUS      OFF
    TYPE        LINE
 
    CLASSITEM   "CLASS"
    CLASS
      NAME 'State Boundary'
      EXPRESSION 'land'
      STYLE
        COLOR      64 64 64
      END
    END
  END # States line layer ends here
  # End of LAYER DEFINITIONS-------------------------------
 
END# All map files must come to an end just as all other things must come to..
 
MapFile结构
下面是mapfile内的对象结构:
MAP
(states_poly)LAYER----------|---------LAYER (states_line)
(land)CLASS-----|-CLASS (water)         |-CLASS
STYLE-|-LABEL     |-STYLE                 |-STYLE</pre>
LABEL对象和关键字
这里我们再介绍一些LABEL对象相关的参数：
FONTSET
   这里为TrueType字体列表文件指定全路径。这个文件列出了所有可能获得的字体。仔细看这个文件本身和MapServerfontset documentation去获得更多信息。FONTSET是MAP对象的参数。
LABELITEM
   用来指定标注所用的数据属性，本例为”STATE”。LABELITEM是LAYER对象的参数。
LABEL
表示LABEL对象的开始标记。标注对象可以用在其他对象下面（如SCALEBAR对象）。
COLOR
处于LABEL对象内部，指定标注文本的颜色。
SHADOWCOLOR （不推荐使用）
指定标注文本阴影颜色。
注意：从MapServer6开始，GEOMTRANSFORM LABELPOLY的LABEL STYLE必须使用。本教程还未更新。
SHADOWSIZE  (不推荐使用)
指定阴影尺寸。此值以像素单位代表X,Y的偏移值。所以，“2 2”意味着两个像素宽和两个像素高。
注意：从MapServer6开始，GEOMTRANSFORM LABELPOLY的LABEL STYLE必须使用。本教程还未更新。
TYPE
在LABEL对象内部指定使用哪种类型字体。我们可以选择TRUETYPE或BITMAP(内置字体)。我们选择TRUETYPE。
FONT
   如果你指定TYPE为TRUETYPE，你需要指定使用的是哪种字体。这里使用的是字体列表文件中的“alias”。
SIZE
   如果使用的是truetype字体，此值代表字体像素尺寸大小。如果是位置，你会看到如”small”或”large”的字样。
ANTIALIAS
用来打开truetype字体抗锯齿功能打开或关闭。记住这个值不是on或off，而是TRUE或FALSE。
POSITION
指定相对于标注点标注文本的位置。它是垂直和水平位置的联合体。你可以将垂直对齐设置为：C表示中间，U表示上，L代表下。水平对齐可设置为：C代表中间，L代表左，R代表右。所以，为了将标注文本对齐到标注ID中间，你要使用“CC“（中间-中间）。或者你想对齐在ID的左下方，你要使用”LL”.另一个办法是让MapServer来决定标签的最佳位置，这时你要使用”AUTO”。
PARTIALS
告诉MapServer是否需要生成不完整的标注文本。默认的是不生成标注文本的片断。这个值要么是TRUE要么是FALSE。
MINDISTANCE
指定重复标签间的最小距离像素值。增加或减小这个值看看会发生什么。
BUFFER
每个标注的像素填充值。这个用来增强可读性。BUFFER值为4个像素值意味着在一个标注的4个像素内是不会画其他标注的。你也可以改变这个值看它是怎么作用的。
 
你也可以独立于POLYGON层创建标注。你要用ANNOTATION数据类型来实现这个功能。看看下一个例子了解你要如何实现这种标注。你会注意到”label”对象内的CLASS对象有一个COLOR参数，它的值为”-1 -1 -1”。负值告诉MapServer给CLASS透明色（标注ID不需要显示）。再一次的，玩味一下参数的值去了解它是如何作用于地图的。
 
 
PS:中文版权为asswclw所有，请尊重劳动成果，转载将注明出处。