Static map with two layers

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In this example, the image is generated to the source of the URL connection <img> Label:

//webgis.pub/cgi-bin/mapserv?map=/owg/mfa2.map&layer=world-country&layer=country-line&mode=map

Most traditional MapServer examples are shown in this way.

This example is slightly different from the previous one, where the color of the polygon has been modified.

Mapfile description

First take a look at the MapFile that this example uses mfa2.map ), This Mapfile defines two layers:

01 MAP
02     IMAGETYPE "PNG"
03     EXTENT -180 -90 180 90
04     SIZE 600 300
05     SHAPEPATH "/gdata"
06     IMAGECOLOR 255 255 255
07     LAYER
08         NAME "world-country"
09         DATA "wcountry.shp"
10         STATUS OFF
11         TYPE POLYGON
12         CLASS
13             NAME "States"
14             STYLE
15                 COLOR 232 232 232
16             END
17         END
18     END
19     LAYER
20         NAME "country-line"
21         DATA "wcountry.shp"
22         STATUS OFF
23         TYPE LINE
24         CLASS
25             NAME "State Boundary"
26             STYLE
27                 COLOR 132 132 32
28             END
29         END
30     END
31 END

It's important to remember that MapServer's render layers are in the order they are specified in the mapfile. The last layer in the Mapfile is the top layer of the map rendering result, building the map on top of all the previous layers. This means that details shown earlier in the Mapfile (ie, lower layers in the map image) may be obscured. This is most important when rendering polygon layers, since polygons can be filled with a specified color. If the map server renders a point layer (that is, for example, the location of a city), then the render state represents a polygon layer, and the city will not be visible unless the specified polygon layer color is transparent.

This problem is easily remedied by defining the polygon layer in front. Polygons can also be rendered as a series of lines (ie, a line layer). Since a line is one-dimensional, there is no area to fill, so the details of the layers below are still visible. When there is no fill color, the specified color is: -1,-1,-1, which can also achieve the effect of transparency.

The structure of MapFile looks like this:

MAP
    LAYER
        CLASS
            STYLE
    LAYER
        CLASS
            STYLE

Compared to the previous Mapfile, the changes are as follows:

Here, the original layer is divided into two layers. The first layer is still a polygon layer, but there is no OUTLINECOLOR attribute in the style anymore. The TYPE of the second layer is LINE and the color value is different from the OUTLINECOLOR in the first example. This produces a slightly different image from the first example.

Further explanation

Here is an explanation of why this is done. If we continue to add layers on top of the state layer, the contours are most likely to be masked by these layers. To be able to see the borders and add other layers, we have to separate the borders layer from the state polygon layer and place it on top of the other other layers. There is an order in how to define/add layers, which will be explained later. Here you just need to remember according to "Later on top" (layers defined later will be displayed on the top).