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

1、前言

　　MapServer不只支持矢量數據（point, lines, polygons, and annotations），同時也支持柵格數據。經過GDAL庫，MapServer能夠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、灰度圖像或僞彩色圖像。

　　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

　　注意 在使用RGB和多光譜圖像時，可能會出現明顯的性能問題。

　　由於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。所以，除了8位（灰度圖像或僞彩色圖像）png8以外，如今還可使用png（真顏色）進行輸出。此示例使用PNG做爲ImageType。

　　注意 與RGB輸入同樣，與PNG8相比，使用PNG時可能會出現明顯的性能問題。

　　MapServer實際上也可使用gdal生成輸出圖像，但這是另外一個主題。若是您想了解更多信息，請查看mapfile引用中的outputformat對象。

2、建立站點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的內容以下

<?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 中的全部內容拷貝到 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中建立站點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。此處須要表達的是標籤，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

　　　　

3、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

 　　　　當前案例分爲四個圖層：

• • • tsates用來展現幾何區域
    • modis展現tiff圖像文件，柵格數據
    • states_line展現的是CLASSITEM=CLASS，EXPRESSION=land 的線條數據，其中線條符號爲 line5 

# 12
Symbol
NAME 'line5'
Type VECTOR
TRANSPARENT 0
Points
1 0
0 1
0 1
1 0
END
END 

#line的數據類型爲 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
#此處能夠理解爲構建了一個矢量區域，有個座標系，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，長爲 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 中的點數據來展現，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。可使絕對路徑，也能夠是和mapfile（example1_5.map）的相對路徑。字符集位置。能夠先了解一下SYMBOL，資料以下：

　　　　　　SYMBOL的講解：https://www.mapserver.org/mapfile/symbol.html

　　　　　　建立字符集文件：https://www.mapserver.org/mapfile/symbology/construction.html

　　　　DATA raster/mod09a12003161_ugl_ll_8bit.tif

　　　　　　在NAME爲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。這個圖層爲柵格類型。這個圖層是經過GDAL的庫來完成支持的。MapSeerver上不一樣的柵格支持和生成請查看：https://www.mapserver.org/input/raster.html#raster

　　　　　　modis數據瞭解請進：https://modis.gsfc.nasa.gov/

　　　　TYPE RASTER

　　　　　　在NAME爲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"

　　　　　　這個位置我以爲很難理解。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源碼中經過RasterIO來讀取波段數據。

　　　　　　TIFF文件時位圖，在windows中的存儲格式爲BGR，而後MapServer根據參數調用時，對參數作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麼。知道讀到or ignore以後。忽略，這個tif文件正好背景顏色值RGB是：71 74 65 ，是否設置OFFSITE值和背景顏色值同樣時，作忽略處理。

　　　　　　可是在設置爲其餘顏色值時，卻仍是顯示當前tif文件的背景顏色。這就十分尷尬了，是不是由於當前tif文件有背景顏色，而後將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（僞彩色圖像）。還有：RGB、RGBA等。

4、RGB vs Indexed Color Image 真彩色和僞彩色的對比

　　1.關於僞彩色，能夠查看：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

 　　修改成

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。

5、後記

　　感受模擬樣例作一個很簡單，可是弄清楚相關的mapfile對象卻很頭痛，涉及的知識點太多，不理解的位置太多。好比：OFFSITE就不動。繼續深刻學習，相信隨着瞭解的愈來愈多，就會知道其做用。