ArcGIS API For Flex对ImageServer发布的服务进行渲染及RasterFunction支持函数（学习笔记）

ArcGIS Server中的 Image Service 能够提供对影像原始数据的动态访问，得到其元数据（metadata）：
包括自定义的空间参考，图幅范围，像元大小，像元类型，波段数，以及各波段的基础统计信息（最小值，最大值，平均值之
类）；能够根据相关参数生成新的影像，同时在arcgis server 10版本中还添加了针对栅格数据的查询和下载功能。最重要的是不同
于map service（不论是cache或non-cache），能够对影像做一些处理，比如计算NDVI，坡度，坡向，进行Standard Deviation拉
伸、直方图均匀化拉伸，minmax拉伸等基本处理。虽然和专门的影像处理软件完全不能比较，但是能在网络上进行遥感影像处理。
为了能利用ArcGIS Flex API浏览ImageServer服务并对栅格地图进行渲染，我参考了ArcGIS有关服务的帮助和例子http:/
/help.arcgis.com/en/webapi/flex/samples/index.html#/Shaded_relief_raster_function/01nq00000066000000/里面
讲解了ImageServer服务几种栅格渲染的方法，ArcGISImageServiceLayer是通过renderingRule来进行渲染的，
但renderingRule的类型为RasterFunction，看到RasterFunction中的functionName和arguments属性，这让我一头雾水。

后来经过大量的搜查，终于被我从ArcGIS Server REST API的帮助中找到，functionName为RasterFunction的函数名，
arguments为实现该函数的参数，下面是RasterFunction支持的函数：

"rasterFunction" : "Aspect"

The

Aspect

raster function takes no arguments. Hence, specifying only the

rasterFunction

property
suffices in this case.

{
"rasterFunction" : "Aspect"
}

"rasterFunction" : "Colormap"

The arguments for the

Colormap

function are as shown below:

{
"rasterFunction" : "Colormap",
"rasterFunctionArguments" : {
"ColormapName" : "<Random | NDVI | Elevation | Gray>",
"Colormap" : [
[<value1>, <red1>, <green1>, <blue1>], //[int, int, int, int]
[<value2>, <red2>, <green2>, <blue2>]
]
},
"variableName" : "Raster"
}

Example 1:

{
"rasterFunction" : "Colormap",
"rasterFunctionArguments" : {
"ColormapName" : "Random"
},
"variableName" : "Raster"
}

Example 2:

{
"rasterFunction" : "Colormap",
"rasterFunctionArguments" : {
"Colormap" : [
[0, 1, 2, 3],
[2, 45, 52, 13]
]
},
"variableName" : "Raster"
}

"rasterFunction" : "Hillshade"

The arguments for the

Hillshade

function are as shown below:

{
"rasterFunction" : "Hillshade",
"rasterFunctionArguments" : {
"Azimuth" : <Azimuth>, //double (e.g. 215.0)
"Altitude" : <Altitude>, //double (e.g. 75.0)
"ZFactor" : <ZFactor> //double (e.g. 0.3)
},
"variableName" : "DEM"
}

Example:

{
"rasterFunction" : "Hillshade",
"rasterFunctionArguments" : {
"Azimuth" : 215.0,
"Altitude" : 75.0,
"ZFactor" : 0.3
},
"variableName" : "DEM"
}

"rasterFunction" : "NDVI"

The arguments for the

NDVI

function are as shown below:

{
"rasterFunction" : "NDVI",
"rasterFunctionArguments" : {
"VisibleBandID" : <VisibleBandID>, //int (zero-based band id, e.g. 2)
"InfraredBandID" : <InfraredBandID> //int (zero-based band id, e.g. 1)
},
"variableName" : "Raster"
}

Example:

{
"rasterFunction" : "NDVI",
"rasterFunctionArguments" : {
"VisibleBandID" : 2,
"InfraredBandID" : 1
},
"variableName" : "Raster"
}

"rasterFunction" : "ShadedRelief"

The arguments for the

ShadedRelief

function are as shown below:

{
"rasterFunction" : "ShadedRelief",
"rasterFunctionArguments" : {
"Azimuth" : <Azimuth>, //double (e.g. 215.0)
"Altitude" : <Altitude>, //double (e.g. 75.0)
"ZFactor" : <ZFactor>, //double (e.g. 0.3)
"Colormap" : [
[<value1>, <red1>, <green1>, <blue1>], //[int, int, int, int]
[<value2>, <red2>, <green2>, <blue2>]
]
},
"variableName" : "Raster"
}

Example:

{
"rasterFunction" : "ShadedRelief",
"rasterFunctionArguments" : {
"Azimuth" : 215.0,
"Altitude" : 75.0,
"ZFactor" : 0.3,
"Colormap" : [
[0, 1, 2, 3],
[2, 45, 52, 13]
]
},
"variableName" : "Raster"
}

"rasterFunction" : "Slope"

The arguments for the

Slope

function are as shown below:

{
"rasterFunction" : "Slope",
"rasterFunctionArguments" : {
"ZFactor" : <ZFactor> //double (e.g. 0.3)
},
"variableName" : "DEM"
}

Example:

{
"rasterFunction" : "Slope",
"rasterFunctionArguments" : {
"ZFactor" : 0.3
},
"variableName" : "DEM"
}

"rasterFunction" : "Statistics"

The arguments for the

Statistics

function are as shown below:

{
"rasterFunction" : "Statistics",
"rasterFunctionArguments" : {
"Type" : "<Min | Max | Mean | StandardDeviation>",
"KernelColumns" : <KernelColumns>, //int (e.g. 3)
"KernelRows" : <KernelRows> //int (e.g. 3)
},
"variableName" : "Raster"
}

Example:

{
"rasterFunction" : "Statistics",
"rasterFunctionArguments" : {
"Type" : "Mean",
"KernelColumns" : 3,
"KernelRows" : 3
},
"variableName" : "Raster"
}

"rasterFunction" : "Stretch"

The arguments for the

Stretch

function are as shown below:

{
"rasterFunction" : "Stretch",
"rasterFunctionArguments" : {
"StretchType" : <StretchType>, //int (0 = None, 3 = StandardDeviation, 4 = Histogram Equalization, 5 = MinMax)
"NumberOfStandardDeviations" : <NumberOfStandardDeviations>, //int (e.g. 2)
"Statistics" : [
[<min1>, <max1>, <mean1>, <standardDeviation1>], //[double, double, double, double]
[<min2>, <max2>, <mean2>, <standardDeviation2>]
],
"Gamma" : [<gamma1>, <gamma2>] //array of doubles
},
"variableName" : "Raster"
}

Example:

{
"rasterFunction" : "Stretch",
"rasterFunctionArguments" : {
"StretchType" : 3,
"NumberOfStandardDeviations" : 2,
"Statistics" : [
[0.2, 222.46, 99.35, 1.64],
[5.56, 100.345, 45.4, 3.96],
[0, 352.37, 172.284, 2]
],
"Gamma" : [1.25, 2, 3.95]
},
"variableName" : "Raster"
}

我们可以从上面的函数中利用ShadedRelief函数完成渲染，有关代码如下：

rasterArgs = {};
rasterArgs["Colormap"] = ColorsGradient([new Color(150,255,255),new Color(255,255,150),new Color(255,150,150)]);                       //ColorsGradient上一篇文章所写的函数
rasterArgs["Azimuth"] =215;
rasterArgs["Altitude"] =75;
rasterFunction.arguments=rasterArgs;
rasterFunction.functionName = "ShadedRelief";
imageLayer.renderingRule = rasterFunction;    //imageLayer为ArcGISImageServiceLayer

这样就可以进行渲染了，但是值得我们注意的是，服务中栅格数据到底是离散型还是连续型的，上面提到的函数都针对不同的数据类型。