Raster function (service)

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//
// Copyright 2017 Esri.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

import UIKit
import ArcGIS

class RasterFunctionServiceViewController: UIViewController {
    @IBOutlet private weak var mapView: AGSMapView!
    private var map: AGSMap?
    private var imageServiceRaster: AGSImageServiceRaster?

    override func viewDidLoad() {
        super.viewDidLoad()

        // Add the source code button item to the right of navigation bar
        (navigationItem.rightBarButtonItem as! SourceCodeBarButtonItem).filenames = ["RasterFunctionServiceViewController"]

        // Initialize map and set it on map view
        map = AGSMap(basemapStyle: .arcGISDarkGrayBase)
        mapView.map = map

        // Initialize image service raster and apply raster function when it's loaded
        imageServiceRaster = AGSImageServiceRaster(url: URL(string: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/NLCDLandCover2001/ImageServer")!)
        imageServiceRaster?.load { [weak self] (error) in
            if let error = error {
                self?.presentAlert(error: error)
            } else {
                // Set map view's viewpoint to the image service raster's full extent
                if let center = self?.imageServiceRaster?.serviceInfo?.fullExtent?.center {
                    self?.mapView.setViewpoint(AGSViewpoint(center: center, scale: 58000000.0))
                }

                // Apply raster function
                self?.applyRasterFunction()
            }
        }
    }

    func applyRasterFunction() {
        // Define the JSON string needed for the raster function
        let rasterFunctionJSONString = """
            {
              "raster_function_arguments":
              {
                "z_factor":{"double":25.0,"type":"Raster_function_variable"},
                "slope_type":{"raster_slope_type":"none","type":"Raster_function_variable"},
                "azimuth":{"double":315,"type":"Raster_function_variable"},
                "altitude":{"double":45,"type":"Raster_function_variable"},
                "type":"Raster_function_arguments",
                "raster":{"name":"raster","is_raster":true,"type":"Raster_function_variable"},
                "nbits":{"int":8,"type":"Raster_function_variable"}
              },
              "raster_function":{"type":"Hillshade_function"},
              "type":"Raster_function_template"
            }
            """

        // NOTE: You can alternatively create the raster function via a JSON string that is contained in a
        // file on disk (ex: hillshade_simplified.json) via the constructor: AGSRasterFunction(fileURL: <#T##URL#>)

        // Create a raster function from the JSON string
        if let rasterFunction = AGSRasterFunction.fromJSON(rasterFunctionJSONString, error: nil) as? AGSRasterFunction {
            if let imageServiceRaster = imageServiceRaster {
                //
                // Get the raster function arguments
                let rasterFunctionArguments = rasterFunction.arguments

                // Get first raster name from raster function arguments
                let rasterName = rasterFunctionArguments?.rasterNames.first

                // Set image service raster in the raster function arguments with name
                rasterFunctionArguments?.setRaster(imageServiceRaster, withName: rasterName!)

                // Create new raster with raster function
                let raster = AGSRaster(rasterFunction: rasterFunction)

                // Create a new raster layer from the raster
                let rasterLayer = AGSRasterLayer(raster: raster)

                // Add raster layer as operational layer
                map?.operationalLayers.add(rasterLayer)
            }
        }
    }
}