A colormap renderer transforms pixel values in a raster to display raster data based on specific colors, aiding in visual analysis of the data. For example, a forestry commission may want to quickly visualize areas above and below the tree-line line occurring at a known elevation on a raster containing elevation values. They could overlay a transparent colormap set to color those areas below the tree-line elevation green, and those above white.
How to use the sample
Pan and zoom to explore the effect of the colormap applied to the raster.
How it works
Create a Raster from a raster file.
Create a RasterLayer from the raster.
Create a List<Integer> representing colors. Colors at the beginning of the list replace the darkest values in the raster and colors at the end of the list replaced the brightest values of the raster.
Create a ColormapRenderer with the color list: ColormapRenderer(colors), and apply it to the raster layer with rasterLayer.setRasterRenderer(colormapRenderer).
The raster used in this sample shows an area in the south of the Shasta-Trinity National Forest, California.
Tags
colormap, data, raster, renderer, visualization
Sample Code
MainActivity.java
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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.
*
*/package com.esri.arcgisruntime.sample.colormaprenderer;
import java.util.ArrayList;
import java.util.List;
import android.graphics.Color;
import android.os.Bundle;
import android.util.Log;
import android.widget.Toast;
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.Basemap;
import com.esri.arcgisruntime.mapping.BasemapStyle;
import com.esri.arcgisruntime.mapping.view.MapView;
import com.esri.arcgisruntime.raster.ColormapRenderer;
import com.esri.arcgisruntime.raster.Raster;
/**
* A sample class which demonstrates the ColorMapRenderer.
*/publicclassMainActivityextendsAppCompatActivity{
privatefinalstatic String TAG = MainActivity.class.getSimpleName();
private MapView mMapView;
@OverrideprotectedvoidonCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// retrieve the MapView from layout mMapView = findViewById(R.id.mapView);
// 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 from a local raster file Raster raster = new Raster(getExternalFilesDir(null) + getString(R.string.shasta_b_w));
// create a raster layerfinal RasterLayer rasterLayer = new RasterLayer(raster);
// create a Map with imagery basemap ArcGISMap map = new ArcGISMap(BasemapStyle.ARCGIS_IMAGERY);
// add the map to a map view mMapView.setMap(map);
// add the raster as an operational layer map.getOperationalLayers().add(rasterLayer);
// create a color map where values 0-149 are red (Color.RED) and 150-250 are yellow (Color.Yellow) List<Integer> colors = new ArrayList<>();
for (int i = 0; i <= 250; i++) {
if (i < 150) {
colors.add(i, Color.RED);
} else {
colors.add(i, Color.YELLOW);
}
}
// create a colormap renderer ColormapRenderer colormapRenderer = new ColormapRenderer(colors);
// set the ColormapRenderer on the RasterLayer rasterLayer.setRasterRenderer(colormapRenderer);
// set Viewpoint on the Raster rasterLayer.addDoneLoadingListener(new Runnable() {
@Overridepublicvoidrun(){
if (rasterLayer.getLoadStatus() == LoadStatus.LOADED) {
mMapView.setViewpointGeometryAsync(rasterLayer.getFullExtent(), 50);
} else {
String error = "RasterLayer failed to load: " + rasterLayer.getLoadError().getMessage();
Log.e(TAG, error);
Toast.makeText(MainActivity.this, error, Toast.LENGTH_LONG).show();
}
}
});
}
@OverrideprotectedvoidonPause(){
super.onPause();
mMapView.pause();
}
@OverrideprotectedvoidonResume(){
super.onResume();
mMapView.resume();
}
@OverrideprotectedvoidonDestroy(){
super.onDestroy();
mMapView.dispose();
}
}