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3.4. MapServer交互：图层控制

  • 作者：卜坤

  • 更新时间：2022-10/7

3.4.1. 如何控制层

能够打开和关闭地图层是Web地图应用程序的标准功能，有许多方法可以使用表单对象作为控件来实现这一点。可以使用下拉框/菜单、复选框和/或单选按钮。在本例中，您将看到如何使用复选框和拖放框实现层选择。

下面是对应的Mapfile：

 1MAP
 2    IMAGETYPE "PNG"
 3    EXTENT -180 -90 180 90
 4    SIZE 600 300
 5    SHAPEPATH "/gdata"
 6    IMAGECOLOR 255 255 255
 7    FONTSET "../fonts/fonts.list"
 8    PROJECTION
 9        "init=epsg:4326"
10    END
11    TEMPLATEPATTERN "tmpl-*"
12    WEB
13        TEMPLATE "to be replaced by map_web_template variable in section2.html"
14        IMAGEPATH "/owg/ms_tmp/"
15        IMAGEURL "/ms_tmp/"
16        METADATA
17            "wms_title" "WMS Demo Server"
18            "wms_onlineresource" "http://192.168.4.211/cgi-bin/mapserv?map=/mstu/htdocs/example2.map&"
19            "wms_srs" "EPSG:3857 EPSG:4326"
20        END
21    END
22    LAYER
23        NAME "land"
24        DATA "land_shallow_topo_8192.tif"
25        STATUS OFF
26        TYPE RASTER
27    END
28    LAYER
29        NAME "topo"
30        TYPE RASTER
31        CONNECTIONTYPE WMS
32        CONNECTION "http://wcs.osgeo.cn:8088/service?"
33        METADATA
34            "wms_srs" "EPSG:4326"
35            "wms_name" "maplet_i887"
36            "wms_server_version" "1.1.1"
37            "wms_format" "image/jpeg"
38        END
39        PROJECTION
40            "init=epsg:4326"
41        END
42    END
43    LAYER
44        NAME "states_poly"
45        DATA "wcountry.shp"
46        STATUS OFF
47        TYPE POLYGON
48        LABELITEM "NAME"
49        CLASS
50            NAME "States"
51            STYLE
52                COLOR 232 232 232
53            END
54        END
55    END
56    LAYER
57        NAME "states_line"
58        DATA "wcountry.shp"
59        STATUS OFF
60        TYPE LINE
61        CLASS
62            NAME "State Boundary"
63            STYLE
64                COLOR 132 132 32
65            END
66        END
67    END
68    LAYER
69        NAME "wriver"
70        DATA "wriver.shp"
71        STATUS OFF
72        TYPE LINE
73        CLASS
74            NAME "World River"
75            STYLE
76                COLOR 0 0 255
77            END
78        END
79    END
80    LAYER
81        NAME "wroads"
82        DATA "wroads.shp"
83        STATUS OFF
84        TYPE LINE
85        CLASS
86            NAME "World Road"
87            STYLE
88                COLOR 100 200 100
89            END
90        END
91    END
92END

请注意图层 STATUS 是如何更改为 OFF 的，除了“States”多边形背景。州背景是默认的，所以地图在没有打开任何层的情况下绘制时，总是会有一些东西。应用程序的用户应该能够控制打开或关闭哪些层。

如果查看以下内容，将会了解MapServ如何打开/关闭这些层：

<form method="get" action="/cgi-bin/mapserv" role="form">
    <fieldset>
        <legend>Layer control form</legend>
        <br>
        <!-- The following two variables are user defined variables.
             MapServer will pass its value to the HTML template if the
             proper tags are found, in square brackets "[]"  -->
        <input type="hidden" name="root" value="/owg">
        <input type="hidden" name="program" value="/cgi-bin/mapserv">
        <!-- The map and layer variables are internal MapServer variables.
             They are required by the mapping application. -->
        <input type="hidden" name="map" value="/owg/mfu3.map">
        <input type="hidden" name="layer" value="states_poly">
        <input type="hidden" name="zoom" value="0">
        <!-- The map_web_template variable will replace the TEMPLATE
             parameter in the WEB object of the MAP file... -->
        <div class="col-sm-12">
            <div class="col-sm-3">
                <select name="map_web" class="form-control">
                    <option value="template tmpl-example-u3.html">Layer control</option>
                </select>
            </div>
            <div class="col-sm-2">
                <input type="submit" name="submit" value="Open the tutorial" class="btn btn-primary">
            </div>
        </div>
    </fieldset>
</form>

3.4.2. 打开和关闭地图图层

可以通过以下链接直接打开演示：

<a href="/cgi-bin/mapserv?map=/owg/mfu3.map&layer=states_line&zoom=0&mode=browse&root=/mstuto&program=/cgi-bin/mapserv&map_web=template+tmpl-example-u3.html"
           target="_blank">Open layer control page</a>
<hr/>

下面显示了一个表单提交，各种参数通过隐藏的 input 控制力。效果同上：

<form method="get" action="/cgi-bin/mapserv" role="form">
    <fieldset>
        <legend>Layer control form</legend>
        <br>
        <!-- The following two variables are user defined variables.
             MapServer will pass its value to the HTML template if the
             proper tags are found, in square brackets "[]"  -->
        <input type="hidden" name="root" value="/owg">
        <input type="hidden" name="program" value="/cgi-bin/mapserv">
        <!-- The map and layer variables are internal MapServer variables.
             They are required by the mapping application. -->
        <input type="hidden" name="map" value="/owg/mfu3.map">
        <input type="hidden" name="layer" value="states_poly">
        <input type="hidden" name="zoom" value="0">
        <!-- The map_web_template variable will replace the TEMPLATE
             parameter in the WEB object of the MAP file... -->
        <div class="col-sm-12">
            <div class="col-sm-3">
                <select name="map_web" class="form-control">
                    <option value="template tmpl-example-u3.html">Layer control</option>
                </select>
            </div>
            <div class="col-sm-2">
                <input type="submit" name="submit" value="Open the tutorial" class="btn btn-primary">
            </div>
        </div>
    </fieldset>
</form>

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