Apply function to raster from file

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// Copyright 2025 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
//
//   https://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 'dart:io';

import 'package:arcgis_maps/arcgis_maps.dart';
import 'package:arcgis_maps_sdk_flutter_samples/common/common.dart';
import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';

class ApplyFunctionToRasterFromFile extends StatefulWidget {
  const ApplyFunctionToRasterFromFile({super.key});

  @override
  State<ApplyFunctionToRasterFromFile> createState() =>
      _ApplyFunctionToRasterFromFileState();
}

class _ApplyFunctionToRasterFromFileState
    extends State<ApplyFunctionToRasterFromFile>
    with SampleStateSupport {
  // Create a controller for the map view.
  final _mapViewController = ArcGISMapView.createController();
  // Raster layer to display raster data on the map.
  late RasterLayer _rasterLayer;
  // A flag for when the map view is ready and controls can be used.
  var _ready = false;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Stack(
        children: [
          ArcGISMapView(
            controllerProvider: () => _mapViewController,
            onMapViewReady: onMapViewReady,
          ),
          // Display a progress indicator and prevent interaction until state is ready.
          LoadingIndicator(visible: !_ready),
        ],
      ),
    );
  }

  Future<void> onMapViewReady() async {
    // Create a map with a standard imagery basemap style.
    final map = ArcGISMap.withBasemapStyle(BasemapStyle.arcGISImageryStandard);
    // Add map to the map view.
    _mapViewController.arcGISMap = map;
    // Load the raster layer.
    await loadRasterLayer();
    // Add the raster layer to the map.
    map.operationalLayers.add(_rasterLayer);
    // Set the viewpoint to the center of the raster layer's full extent.
    final fullExtent = _rasterLayer.fullExtent;
    if (fullExtent != null) {
      final center = fullExtent.center;
      const scale = 80000.0;
      await _mapViewController.setViewpointCenter(center, scale: scale);
    }
    // Set the ready state variable to true to enable the sample UI.
    setState(() => _ready = true);
  }

  Future<void> loadRasterLayer() async {
    // Download the raster file and the color json file.
    await downloadSampleData([
      'b051f5c3e01048f3bf11c59b41507896',
      '5356dbf91788474493467519e268cf87',
    ]);
    // Get the application documents directory.
    final appDir = await getApplicationDocumentsDirectory();
    // Create and load a Raster from the local tif file.
    final shastaElevationRaster = Raster.withFileUri(
      Uri.file('${appDir.absolute.path}/Shasta_Elevation/Shasta_Elevation.tif'),
    );
    await shastaElevationRaster.load();
    // Load the color configuration from the JSON file located in the app's directory.
    final file = File('${appDir.absolute.path}/color.json');
    final rasterColorJson = await file.readAsString();

    // Create a RasterFunction.
    final rasterFunction = RasterFunction.fromJson(rasterColorJson);
    if (rasterFunction != null) {
      final arguments = rasterFunction.arguments;
      if (arguments != null) {
        final rasterNames = arguments.rasterNames;
        // Set the raster function arguments as required by the function used.
        arguments.setRaster(
          name: rasterNames[0],
          raster: shastaElevationRaster,
        );
        arguments.setRaster(
          name: rasterNames[1],
          raster: shastaElevationRaster,
        );
        // Create a Raster from the raster function.
        final raster = Raster.withFunction(rasterFunction);
        // Load the Raster Layer.
        _rasterLayer = RasterLayer.withRaster(raster);
        _rasterLayer.opacity = 0.5;
        await _rasterLayer.load();
      }
    }
  }
}