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

 

  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。