When you generate a map, MapServer automatically performs multiple tasks. It annotates features and prevents conflicts between adjacent dimensions. It provides the use of bitmapped and TrueType fonts.
MapServer has a very flexible annotation engine. It supports local bitmaps and TrueType fonts. Font scaling uses TrueType support. The angle and placement of the dimensions can be customized.
Here is the map file(mfa4.map):
01 MAP
02 IMAGETYPE "PNG"
03 EXTENT -180 -90 180 90
04 SIZE 600 300
05 SHAPEPATH "/gdata"
06 IMAGECOLOR 255 255 255
07 FONTSET "../fonts/fonts.list"
08 LAYER
09 NAME "states_poly"
10 DATA "wcountry.shp"
11 STATUS OFF
12 TYPE POLYGON
13 LABELITEM "NAME"
14 CLASS
15 NAME "States"
16 STYLE
17 COLOR 232 232 232
18 END
19 LABEL
20 COLOR 132 31 31
21 SHADOWCOLOR 218 218 218
22 SHADOWSIZE 2 2
23 TYPE TRUETYPE
24 FONT "arial-bold"
25 SIZE 8
26 ANTIALIAS TRUE
27 POSITION CC
28 PARTIALS FALSE
29 MINDISTANCE 300
30 BUFFER 4
31 END
32 END
33 END
34 LAYER
35 NAME "states_line"
36 DATA "wcountry.shp"
37 STATUS OFF
38 TYPE LINE
39 CLASS
40 NAME "State Boundary"
41 STYLE
42 COLOR 132 132 32
43 END
44 END
45 END
46 END
Annotated Mapfile
The file contains the font alias font location determined by the FONTSET
Keyword assignment.
In order to label each city district with an attribute in the shapefile, determine the name as the value of the LABELITEM
keyword. When rendering a country feature, the value of the feature's NAME
attribute will be used to create the label.
If you want to look at Shapefiles, there are several ways. You can open the associated DBF file in Excel or other spreadsheet program that can read DBF files, and you can see the feature attribute values. If you just want to find out the name of the attribute, you can use the utility dbfinfo, part of the shapelib library. In addition, the application ogrinfo
provides geographic information, as well as feature values.
Each district will be labelled with the labelling parameters specified in 027 to 030. Label objects start with the keyword Label and end with the keyword END (line 030). Layer object with LABELITEM value set to 'name'. Select the attribute NAME as the source of the label text. Each label will be drawn black and its size will be small. Besides small, you can choose small, medium, large, or huge.
The MapFile structure, by object, looks like this:
MAP (states_poly) LAYER----------|---------LAYER (states_line) (land) CLASS-----|-CLASS (water) |-CLASS STYLE-|-LABEL |-STYLE |-STYLE
The changes in the documents are as follows:
6 | IMAGECOLOR 255 255 255 | 6 | IMAGECOLOR 255 255 255 | ||
n | n | 7 | FONTSET "../fonts/fonts.list" | ||
7 | LAYER | 8 | LAYER | ||
11 | TYPE POLYGON | 12 | TYPE POLYGON | ||
n | 12 | CLASSITEM "NAME" | n | 13 | LABELITEM "NAME" |
13 | CLASS | 14 | CLASS | ||
n | 14 | NAME "China" | n | 15 | NAME "States" |
15 | EXPRESSION "CHINA" | ||||
16 | STYLE | 16 | STYLE | ||
n | 17 | COLOR 232 30 30 | n | 17 | COLOR 232 232 232 |
18 | END | 18 | END | ||
n | 19 | END | n | ||
20 | CLASS | ||||
21 | NAME "Others" | ||||
22 | STYLE | 19 | LABEL | ||
20 | COLOR 132 31 31 | ||||
23 | COLOR 198 198 255 | 21 | SHADOWCOLOR 218 218 218 | ||
22 | SHADOWSIZE 2 2 | ||||
23 | TYPE TRUETYPE | ||||
24 | FONT "arial-bold" | ||||
25 | SIZE 8 | ||||
26 | ANTIALIAS TRUE | ||||
27 | POSITION CC | ||||
28 | PARTIALS FALSE | ||||
29 | MINDISTANCE 300 | ||||
30 | BUFFER 4 | ||||
24 | END | 31 | END | ||
31 | TYPE LINE | 38 | TYPE LINE | ||
n | 32 | CLASSITEM "NAME" | n | ||
33 | CLASS | 39 | CLASS | ||
n | 34 | NAME "China Boundary" | n | 40 | NAME "State Boundary" |
35 | EXPRESSION "land" | ||||
36 | STYLE | 41 | STYLE | ||
t | 37 | COLOR 32 32 32 | t | 42 | COLOR 132 132 32 |
38 | WIDTH 1 | ||||
39 | END | ||||
40 | END | ||||
41 | CLASS | ||||
42 | NAME "Others Boundary" | ||||
43 | STYLE | ||||
44 | COLOR 150 150 150 | ||||
45 | WIDTH 0.4 | ||||
46 | END | 43 | END |
Here, we introduce several parameters and dimension objects:
FONTSET "../fonts/fonts.list"
Here, we specify the file for the list of TrueType fonts (or the full path set of fonts). This file lists each available font. See the file itself and the MapFile reference for more information. The MAP object of FONTSET is a parameter.
The contents of this file are as follows:
01 # This be the fonts list
02 arial Vera.ttf
03 arial-bold VeraBd.ttf
04 arial-italic VeraIt.ttf
05 arial-bold-italic VeraBI.ttf
06 times VeraSe.ttf
07 times-bold VeraSeBd.ttf
08 andale-mono VeraMono.ttf
09 vera_sans Vera.ttf
10 vera_sans-bold VeraBd.ttf
11 vera_sans-italic VeraIt.ttf
12 vera_sans-bold-italic VeraBI.ttf
13 vera_sans_mono VeraMono.ttf
14 vera_sans_mono-bold VeraMoBd.ttf
15 vera_sans_mono-italic VeraMoIt.ttf
16 vera_sans_mono-bold-italic VeraMoBI.ttf
17 vera_serif VeraSe.ttf
18 vera_serif-bold VeraSeBd.ttf
19 simsun simsun.ttc
LABELITEM
In the "STATE"
case, the specified data attribute is used for the annotation. LABELITEM
is a parameter of the layer object.
LABEL
Marks the beginning of the definition LABEL
Object. Dimension objects can be used for other objects (that is, scale bar objects)
COLOR
objects within the callout, color specifies the color of the callout text.SHADOWCOLOR
specifies the shadow color for dimension text.SHADOWSIZE
specifies the size of the shadow. This value corresponds to the transition of pixels atX
andY
. Therefore,2
means two pixels wide by two pixels high.TYPE
in the LABEL object, the type specifies what type of font to use. We have a choice of TrueType or Bitmap (built-in fonts). We chooseTRUETYPE
.FONT
If specified as TrueType, you need to specify what font to use. The value mentioned here is "alias"; the "alias" in the font list file.SIZE
If using a TrueType font, the value in pixels is the size of the dimension. If it's a bitmap, say something like "small" or "big".ANTIALIAS
This turns truetype antialiasing on or off. Remember that the value is notOPEN
orCLOSE
, butTRUE
orFALSE
.POSITION
locates the label point of the label text. The value is a combined vertical and horizontal position. You have the following options:C
for center vertical alignment,U
for upper, andL
for lower. For horizontal alignment you have the following options:C
for center,L
for left, andR
for right. Therefore, to call the center of the callout ID for the text alignment, use the valueCC
(center - center). Or, if you wanted it to be the ID at the bottom left, you would useLL
. Another approach is to let MapServer decide the best location for the label. For this, you can use theAUTO
value.PARTIALS
tells MapServer whether to generate incomplete label text. The default here is to not generate fragments of the label text. The value isTRUE
orFALSE
.MINDISTANCE
is the minimum distance, in pixels, between duplicate annotations. See what happens if you increase or decrease the value.BUFFER
Padding (pixels) of the callout. This is used to improve readability. A buffer of 4 pixels means that no labels will be drawn over the four pixels of each other. Again, change and see how it works.
You can also create dimensions to separate a polygon layer. You do it with the data type of the annotation. Take a look at the MapFile of the following example to see how you implement this tagging. You will find that the "annotation" layer within the class object has color parameter values. -1 -1 -1
. Negative numbers tell MapServer to give this class a transparent color (the callout logo is not displayed). Again, modify these values and view the results to see how it affects the map.
To prevent the map from looking cluttered, MapServer optimizes the labeling according to the scale of the data.
Since version 6.2, MapServer has been able to draw label lines for functions that are problematic in the label space (usually when the label text is larger than the marked polygon). This feature is done through the addition of MS RFC 81: offset labels with leaders. This feature is for polygon annotations only.
31 | END | 31 | END | ||
t | t | 32 | LEADER | ||
33 | GRIDSTEP 40 | ||||
34 | MAXDISTANCE 1000 | ||||
35 | STYLE | ||||
36 | COLOR 200 100 100 | ||||
37 | WIDTH 2 | ||||
38 | END | ||||
39 | END | ||||
32 | END | 40 | END |