Apply mosaic rule to rasters

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Apply mosaic rule to a mosaic dataset of rasters.

Image of apply mosaic rule to rasters

Use case

An image service can use a mosaic rule to mosaic multiple rasters on-the-fly. A mosaic rule can specify which rasters are selected, and how the selected rasters are z-ordered. It can also specify how overlapping pixels from different rasters at the same location are resolved.

For example, when using the "By Attribute" mosaic method, the values in an attribute field are used to sort the images, and when using the "Center" method, the image closest to the center of the display is positioned as the top image in the mosaic. Additionally, mosaic operation allows you to define how to resolve the overlapping cells, such as choosing a blending operation.

Specifying mosaic rules is useful for viewing overlapping rasters. For example, using the "By Attribute" mosaic method to sort the rasters based on their acquisition date allows the newest image to be on top. Using "mean" mosaic operation makes the overlapping areas contain the mean cell values from all the overlapping rasters.

How to use the sample

When the rasters are loaded, choose from a list of preset mosaic rules to apply to the rasters.

How it works

  1. Create an ImageServiceRaster using the service's URL.
  2. Create a MosaicRule object and set it to the mosaicRule property of the image service raster, if it does not specify a mosaic rule.
  3. Create a RasterLayer from the image service raster and add it to the map.
  4. Set the mosaicMethod, mosaicOperation and other properties of the mosaic rule object accordingly to specify the rule on the raster dataset.

Relevant API

  • ImageServiceRaster
  • MosaicMethod
  • MosaicOperation
  • MosaicRule

About the data

This sample uses data from the Amberg, Germany ImageServer which hosts a mosaic dataset containing several orthophoto TIFF images of Amberg, Germany.

Additional information

For more information, see Understanding the mosaicking rules from ArcGIS Desktop documentation. To learn more about how to define certain mosaic rules, see Mosaic rule objects from ArcGIS for Developers.

Tags

image service, mosaic rule, mosaic method, raster

Sample Code

MainActivity.kt
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/*
 * Copyright 2020 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.
 *
 */

package com.esri.arcgisruntime.sample.applymosaicruletorasters

import android.os.Bundle
import android.util.Log
import android.view.View
import android.widget.AdapterView
import android.widget.ArrayAdapter
import android.widget.Spinner
import androidx.appcompat.app.AppCompatActivity
import com.esri.arcgisruntime.ArcGISRuntimeEnvironment
import com.esri.arcgisruntime.layers.RasterLayer
import com.esri.arcgisruntime.loadable.LoadStatus
import com.esri.arcgisruntime.mapping.ArcGISMap
import com.esri.arcgisruntime.mapping.BasemapStyle
import com.esri.arcgisruntime.mapping.Viewpoint
import com.esri.arcgisruntime.mapping.view.MapView
import com.esri.arcgisruntime.raster.ImageServiceRaster
import com.esri.arcgisruntime.raster.MosaicMethod
import com.esri.arcgisruntime.raster.MosaicOperation
import com.esri.arcgisruntime.raster.MosaicRule
import com.esri.arcgisruntime.sample.applymosaicruletorasters.databinding.ActivityMainBinding

class MainActivity : AppCompatActivity() {

    private val TAG = MainActivity::class.java.simpleName

    private val activityMainBinding by lazy {
        ActivityMainBinding.inflate(layoutInflater)
    }

    private val mapView: MapView by lazy {
        activityMainBinding.mapView
    }

    private val spinner: Spinner by lazy {
        activityMainBinding.spinner
    }

    // create an image service raster from a url for an image service
    private val imageServiceRaster: ImageServiceRaster by lazy {
        ImageServiceRaster("https://sampleserver7.arcgisonline.com/server/rest/services/amberg_germany/ImageServer").apply {
            // set its mosaic rule
            if (mosaicRule == null) mosaicRule = MosaicRule()
        }
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(activityMainBinding.root)

        // authentication with an API key or named user is required to access basemaps and other
        // location services
        ArcGISRuntimeEnvironment.setApiKey(BuildConfig.API_KEY)

        // create a raster layer from the image service
        val rasterLayer = RasterLayer(imageServiceRaster)
        // add the raster layer to a new map on the map view
        mapView.map = ArcGISMap(BasemapStyle.ARCGIS_TOPOGRAPHIC).apply {
            operationalLayers.add(rasterLayer)
        }

        // listen for the raster layer to finish loading
        rasterLayer.addDoneLoadingListener {
            // if the raster layer didn't load
            if (rasterLayer.loadStatus != LoadStatus.LOADED) {
                rasterLayer.loadError?.let { error ->
                    Log.e(TAG, "Raster layer failed to load: ${error.cause}")
                }
                return@addDoneLoadingListener
            }
            // set the map's viewpoint to the raster extent
            mapView.setViewpointAsync(Viewpoint(rasterLayer.fullExtent.center, 25000.0))
        }

        // set up the spinner with some predefined mosaic rules
        ArrayAdapter.createFromResource(
            this,
            R.array.mosaic_rules,
            android.R.layout.simple_spinner_item
        ).also { adapter ->
            adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
            spinner.adapter = adapter
        }

        spinner.onItemSelectedListener = object : AdapterView.OnItemSelectedListener {
            override fun onNothingSelected(parent: AdapterView<*>?) {
                setMosaicRule("Default")
            }

            override fun onItemSelected(
                parent: AdapterView<*>,
                view: View?,
                position: Int,
                id: Long
            ) {
                setMosaicRule(parent.getItemAtPosition(position) as String)
            }
        }
    }

    /**
     * Applies one of the predefined mosaic rules to the image service raster.
     *
     * @param ruleName one of "Default", "Northwest", "Center", "By attribute", and "Lock raster"
     */
    private fun setMosaicRule(ruleName: String) {
        imageServiceRaster.mosaicRule = MosaicRule().apply {
            when (ruleName) {
                "Default" -> {
                    mosaicMethod = MosaicMethod.NONE
                }
                "Northwest" -> {
                    mosaicMethod = MosaicMethod.NORTHWEST
                    mosaicOperation = MosaicOperation.FIRST
                }
                "Center" -> {
                    mosaicMethod = MosaicMethod.CENTER
                    mosaicOperation = MosaicOperation.BLEND
                }
                "By attribute" -> {
                    mosaicMethod = MosaicMethod.ATTRIBUTE
                    sortField = "OBJECTID"
                }
                "Lock raster" -> {
                    mosaicMethod = MosaicMethod.LOCK_RASTER
                    lockRasterIds.clear()
                    lockRasterIds.addAll(listOf(1, 7, 12))
                }
                else -> {
                    mosaicMethod = MosaicMethod.NONE
                }
            }
        }
    }

    override fun onResume() {
        super.onResume()
        mapView.resume()
    }

    override fun onPause() {
        mapView.pause()
        super.onPause()
    }

    override fun onDestroy() {
        mapView.dispose()
        super.onDestroy()
    }
}

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