MapServer Tutorial——MapServer7.2.1教程學習——第一節用例實踐：Example1.5 Adding a raster layer
MapServer Tutorial——MapServer7.2.1教程學習——第一節用例實踐：Example1.5 Adding a raster layer
一、前言
MapServer不僅支持矢量數據（point, lines, polygons, and annotations），同時也支持柵格數據。通過GDAL庫，MapServer可以輸入輸出多種類型的柵格數據。
在4.x版本前，MapServer輸出柵格數據僅限於單個圖層、灰度圖像或偽彩色圖像。
當前版本支持RGB圖像和多光譜圖像（多層級multi-layer）。此示例演示如何選擇使用多光譜數據時要顯示的圖層。官網地址：https://www.mapserver.org/tutorial/example1-5.html
註意 在使用RGB和多光譜圖像時，可能會出現明顯的性能問題。
因為MapServer5.x後使用AGG或GD2.x來生成輸出的圖像，它還支持RGB（24位或真彩色）輸出。因此，除了8位（灰度圖像或偽彩色圖像）png8之外，現在還可以使用png（真顏色）進行輸出。此示例使用PNG作為ImageType。
註意 與RGB輸入一樣，與PNG8相比，使用PNG時可能會出現明顯的性能問題。
MapServer實際上也可以使用gdal生成輸出圖像，但這是另一個主題。如果您想了解更多信息，請查看mapfile引用中的outputformat對象。
二、創建站點Example1.5 Adding a raster layer
1.文件準備
在cmd中輸入：cd /d E:\SvnWorkspace\LY_WEB_GIS\branches\Documents\ms4w-mapserver-for-wimdows\release-1911-x64-gdal-2-3-3-mapserver-7-2-1\apps
在cmd中輸入：md Example1.5
在cmd中輸入：cd Example1.5
在cmd中輸入：md data
在cmd中輸入：md logs
在cmd中輸入：md fonts
在cmd中輸入：md symbols
在cmd中輸入：cd.>web.config
在cmd中輸入：cd.>example1_5.map
在cmd中輸入：cd data
在cmd中輸入：md raster
修改web.config的內容如下
<?xml version="1.0" encoding="UTF-8"?> <configuration> <system.webServer> <handlers> <add name="MapServerFastCgi" path="*" verb="*" type="" modules="FastCgiModule"
scriptProcessor="E:\SvnWorkspace\LY_WEB_GIS\branches\Documents\ms4w-mapserver-for-wimdows\release-1911-x64-gdal-2-3-3-mapserver-7-2-1\bin\mapserv.exe"
resourceType="Unspecified" requireAccess="Script" allowPathInfo="false" preCondition="" /> </handlers> <caching enabled="true" enableKernelCache="true" /> </system.webServer> </configuration>
將 app\tutorial\fonts 中的所有內容拷貝到 app\Example1.5\fonts 文件夾中（字體文件）
將 app\tutorial\data 中的 states_ugl.dbf、states_ugl.shp、states_ugl.shx 拷貝到 app\Example1.5\data 文件夾中（數據文件）
將 app\tutorial\symbols 中的 symbols35.sym 拷貝到 app\Example1.5\symbols 文件夾中（符號文件）
將 app\tutorial\data\raster 中的 mod09a12003161_ugl_ll_8bit.tif、mod09a12003161_ugl_ll_idxa.tif 拷貝到 app\Example1.5\data\raster 文件夾中（圖層數據文件）
2.在IIS中創建站點Example1.5
應用程序池名稱：Example1.5；站點端口：8015
3.給應用程序池讀寫log文件夾權限
在cmd中輸入：icacls "E:\SvnWorkspace\LY_WEB_GIS\branches\Documents\ms4w-mapserver-for-wimdows\release-1911-x64-gdal-2-3-3-mapserver-7-2-1\apps\Example1.5\logs" /grant "IIS AppPool\Example1.5":(OI)(CI)RW
4.修改example1_5.map文件
# 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"
SYMBOLSET "./symbols/symbols35.sym"
# Layer objects are defined beneath the map object. You need at least one
# layer defined in your map file before you can display a map... You can
# define as many layers as you‘d like although 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 application to need more than 100 layers in
# your application.
#
# Start of LAYER DEFINITIONS ---------------------------------------------
LAYER # States polygon layer begins here
NAME states
DATA states_ugl
STATUS OFF
TYPE POLYGON
# CLASSITEM defines the non-spatial attribute 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 different for each data format). In this
# example the shapefile states_ugl has an associated database
# (states_ugl.dbf) that contains an attribute called "CLASS". You will be
# using two values in the CLASS attribute to separate the classes (also
# called themes) used in this layer--land and water. CLASSITEM is used in
# association with the EXPRESSION parameter in the CLASS object. See below.
CLASSITEM "CLASS"
# The class object is defined within the layer object. You can define as
# many classes as you need (well, there are limits as with layers, but it‘s
# senseless to define more than ten on a "normal" layer. There are
# situations, however, where you might have to do it.)
CLASS
NAME ‘States‘
EXPRESSION ‘land‘
# There are styles in a class, just like there are classes in a layer,
# just like there are layers in a map. You can define multiple styles in
# a class just as you can define multiple classes in a layer and multiple
# layers in a map.
STYLE
COLOR 232 232 232
END
END
END # States polygon layer ends here
# In addition to vector data (shapefiles are vector data), MapServer supports
# a host of raster formats. In GIS world, one of the most common raster
# formats is GeoTIFF, a TIFF image with geospatial headers. MapServer also
# supports JPEG, PNG, GIF, and other common formats. Other raster formats
# supported by MapServer include ESRI Arc/Info grid, HDF and HDF-EOS, NetCDF,
# Generic raster binaries, OGC Web Map Service (WMS) layers, etc. Pretty much
# any raster format you can think of is probably supported, thanks to the
# impressive Geospatial Data Abstraction Library (GDAL, pronounced "GOODALL"
# or GOODLE?). More information on GDAL is available at http://www.gdal.org.
#
# MapServer 4.x can read and display bitmapped (like GIFs), RGB/A (true
# color), and multispectral (images with more than 3 bands, like raw LandSat
# images) rasters.
LAYER # MODIS raster layer begins here
NAME modis
DATA "raster/mod09a12003161_ugl_ll_8bit.tif"
STATUS OFF
TYPE RASTER
PROCESSING "BANDS=1,2,3"
OFFSITE 71 74 65
END # MODIS raster 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
SYMBOL ‘line5‘
COLOR 64 64 64
SIZE 1
END
END
END # States line layer ends here
# Labels can be defined in its own layer. This is useful if, say, you want
# to label a polygon layer that‘s covered by another layer. By keeping the
# label separate from the polygon and placing it near the bottom of the map
# file (so its drawn on, or near the, top), you can still see the label even
# though you might not be able to see the polygon. It is also a good
# alternate to point symbols.
#
# A label layer is actually defined with ANNOTATION type (This is derived from
# points, Node IDs for lines, or polygon IDs).
LAYER # States label layer begins here
NAME states_label
DATA states_ugl
STATUS OFF
TYPE POLYGON #ANNOTATION 此類型的LAYER已經被移除。此處需要表達的是標簽，請查看上一章《MapServer Tutorial——MapServer7.2.1教程學習——第一節用例實踐：Example 1.4 Labeling the Map》
#LAYER 官網：https://www.mapserver.org/mapfile/layer.html ，定位到 TYPE 對象處查看。
CLASSITEM "CLASS"
# Just like CLASSITEM, LABELITEM defines the database attribute that you
# will be using to draw labels. In this case, the values of the attribute
# "STATE" will be used to label the states polygons.
LABELITEM "STATE"
CLASS
EXPRESSION ‘land‘
STYLE
COLOR -1 -1 -1
END
# There can be labels in a class, just like there are classes in a layer,
# just like there are layers in a map. You can define multiple labels in
# a class just as you can define multiple classes in a layer and multiple
# layers in a map.
# MapServer has a very flexible labeling system. With that flexibility
# comes complexity, specially when using truetype fonts. Please read
# through the LABEL section of the MapServer map file documentation at
# http://www.mapserver.org/mapfile for more information.
LABEL
COLOR 132 31 31
#SHADOWCOLOR 218 218 218 # deprecated, use STYLE and GEOMTRANSFORM
#SHADOWSIZE 2 2 # deprecated, use STYLE and GEOMTRANSFORM
TYPE TRUETYPE
FONT arial-bold
SIZE 12
ANTIALIAS TRUE
POSITION CL
PARTIALS FALSE
MINDISTANCE 300
BUFFER 4
END # end of label
END # end of class
END # States label layer ends here
# End of LAYER DEFINITIONS -------------------------------
DEBUG 5
CONFIG "MS_ERRORFILE" "logs\ms.log"
END # All map files must come to an end just as all other things must come to...
5.瀏覽查看
在瀏覽器中輸入：http://localhost:8015/mapserv?map=../apps/Example1.5/example1_5.map&layer=states&layer=modis&layer=states_line&layer=states_label&mode=map
三、MapFile文件解析
1.文件結構
MAP
LAYER #1-------------LAYER #2----|----LAYER #3--------LAYER #4
(states) (modis) (states_line) (states_label)
| | |
(land) CLASS-|-CLASS (water) |-CLASS |-CLASS
| | | |
STYLE-| |-STYLE |-STYLE STYLE-|-LABEL
當前案例分為四個圖層：
-
-
- tsates用來展示幾何區域
- modis展示tiff圖像文件，柵格數據
- states_line展示的是CLASSITEM=CLASS，EXPRESSION=land 的線條數據，其中線條符號為 line5
-
# 12 Symbol NAME ‘line5‘ Type VECTOR TRANSPARENT 0 Points 1 0 0 1 0 1 1 0 END END
#line的數據類型為 VECTOR 矢量數據，詳情請看：https://www.mapserver.org/mapfile/symbology/construction.html中 Symbols of TYPE vector and ellipse
#同時，請查看：https://www.mapserver.org/mapfile/symbol.html
#此處可以理解為構建了一個矢量區域，有個坐標系，點（1,0）、（0,1）、（0,1）、（1,0）畫了一個矩形，然而此矩形看起來沒有寬度，長為 2 的開方（三角形勾股定理）
#同時，將這個矢量矩形（看起來就是短的線）中心基於 dbf 數據中 CLASS = land 的 POLYGON 中的點數據來展示，這樣看起來就給 land 外面畫了一個線。
2.對象參數解釋
IMAGETYPE
MapServer生成輸出數據的格式。在cmd中輸入：mapserv -v 查看。值PNG是值輸出24位PNG或真色PNG。
SYMBOLSET
SYMBOL集合的文件位置。可以使絕對路徑，也可以是和mapfile（example1_5.map）的相對路徑。字符集位置。可以先了解一下SYMBOL，資料如下：
SYMBOL的講解：https://www.mapserver.org/mapfile/symbol.html
創建字符集文件：https://www.mapserver.org/mapfile/symbology/construction.html
DATA raster/mod09a12003161_ugl_ll_8bit.tif
在NAME為modis的圖層中，添加的是一個GeoTIFF圖層數據。MapServer支持矢量數據和柵格數據。這個圖層為柵格類型。這個圖層是通過GDAL的庫來完成支持的。MapSeerver上不同的柵格支持和生成請查看：https://www.mapserver.org/input/raster.html#raster
modis數據了解請進：https://modis.gsfc.nasa.gov/
TYPE RASTER
在NAME為modis的圖層中，當前LAYER的數據類型。此處使用的是RASTER。同時在LAYER中，MapServer還支持POLYGON，LINE，POINT，LABEL中支持ANNOTATION等。
PROCESSING "BANDS=1,2,3"
這個位置我覺得很難理解。查了相關資料。大概意思是，MapServer調用GDAL庫來處理tiff圖像，並輸出顯示。
PROCESSING表示進程。根據進程值來決定調用那個庫。請查看：https://www.mapserver.org/mapfile/layer.html 中PROCESSING 段落。
BANDS表示波段，GDAL源碼中通過RasterIO來讀取波段數據。
TIFF文件時位圖，在windows中的存儲格式為BGR，然後MapServer根據參數調用時，對參數做了調整順序的相關處理。1,2,3表示Red，Green和blue三種波段選擇。
具體的我也不大清楚，總之嘗試後，發現1,2,3在瀏覽器中顯示的是和直接看到tiff相差不遠，只是灰色的底色變成白色的。
同時也請查看：https://www.mapserver.org/input/raster.html 中 BANDS=red_or_grey[,green,blue[,alpha]] 處的解釋。
OFFSITE
設置當前LAYER層的背景顏值組成。（Sets the color index to treat as transparent for raster layers.）
告訴MapServer按照像素值渲染背景（或忽略）。
想了半天沒弄懂，最後亂改這個值也沒發現什麽。知道讀到or ignore之後。忽略，這個tif文件正好背景顏色值RGB是：71 74 65 ，是否設置OFFSITE值和背景顏色值一樣時，做忽略處理。
但是在設置為其他顏色值時，卻還是顯示當前tif文件的背景顏色。這就十分尷尬了，是否是因為當前tif文件有背景顏色，然後將OFFSITE設置的顏色給覆蓋了。
顏色組成分多種形式，當前案例是：Indexed Color Image（偽彩色圖像）。還有：RGB、RGBA等。
四、RGB vs Indexed Color Image 真彩色和偽彩色的對比
1.關於偽彩色，可以查看：https://en.wikipedia.org/wiki/Indexed_color
2.修改mapfile的相關配置，將
DATA "raster/mod09a12003161_ugl_ll_8bit.tif"
STATUS DEFAULT
TYPE RASTER
PROCESSING "BANDS=1,2,3"
OFFSITE 71 74 65
修改為
DATA "raster/mod09a12003161_ugl_ll_idxa.tif"
STATUS DEFAULT
TYPE RASTER
OFFSITE 70 74 66
看看效果
顯示的效果已經改變。去掉GDAL的程序處理後，也不顯示背景色了。
五、後記
感覺模擬樣例做一個很簡單，但是弄清楚相關的mapfile對象卻很頭痛，涉及的知識點太多，不理解的位置太多。比如：OFFSITE就不動。繼續深入學習，相信隨著了解的越來越多，就會知道其作用。
MapServer Tutorial——MapServer7.2.1教程學習——第一節用例實踐：Example1.5 Adding a raster layer