const { getEarthEngine } = require('./init');
/**
* Export image as GeoTIFF with download link
* @param {object} params - Export parameters
* @returns {Promise<object>} Download URL for GeoTIFF
*/
async function exportToDownload(params) {
const ee = getEarthEngine();
const {
datasetId,
imageId,
startDate,
endDate,
region,
scale = 10, // 10m for Sentinel-2
crs = 'EPSG:4326',
format = 'GeoTIFF',
fileName = `earth_engine_export_${Date.now()}`,
bands = null,
maxPixels = 1e8
} = params;
return new Promise((resolve, reject) => {
try {
let image;
// Create composite if dataset info provided
if (datasetId && startDate && endDate) {
let collection = ee.ImageCollection(datasetId)
.filterDate(startDate, endDate);
if (region) {
const geometry = region.type === 'Point'
? ee.Geometry.Point(region.coordinates).buffer(5000) // 5km buffer for points
: ee.Geometry.Polygon(region.coordinates);
collection = collection.filterBounds(geometry);
}
// Apply cloud masking for Sentinel-2
if (datasetId.includes('S2')) {
collection = collection.map(function(image) {
const qa = image.select('QA60');
const cloudBitMask = 1 << 10;
const cirrusBitMask = 1 << 11;
const mask = qa.bitwiseAnd(cloudBitMask).eq(0)
.and(qa.bitwiseAnd(cirrusBitMask).eq(0));
return image.updateMask(mask)
.select('B.*')
.copyProperties(image, ['system:time_start']);
});
}
// Create median composite
image = collection.median();
// Select specific bands if requested
if (bands && bands.length > 0) {
image = image.select(bands);
}
} else if (imageId) {
image = ee.Image(imageId);
if (bands && bands.length > 0) {
image = image.select(bands);
}
} else {
throw new Error('Either imageId or datasetId must be provided');
}
// Define export region
let exportRegion;
if (region) {
exportRegion = region.type === 'Point'
? ee.Geometry.Point(region.coordinates).buffer(5000)
: ee.Geometry.Polygon(region.coordinates);
} else {
// Use image footprint
exportRegion = image.geometry();
}
// Get band names if not specified
let exportBands = bands;
if (!exportBands) {
// Get actual band names from the image
const bandNames = image.bandNames();
exportBands = bandNames.getInfo();
}
// Get download URL for full-resolution GeoTIFF
// This creates a proper download link for the full image
const downloadUrl = image.select(exportBands).getDownloadURL({
name: fileName,
region: exportRegion,
scale: scale,
crs: crs,
crsTransform: null,
format: format,
maxPixels: maxPixels,
filePerBand: false // Single multi-band GeoTIFF file
});
// Generate preview with proper band selection for visualization
let previewImage;
if (exportBands.length >= 3) {
// Use first 3 bands for RGB preview
previewImage = image.select(exportBands.slice(0, 3));
} else if (exportBands.length === 2) {
// For 2 bands, create RGB visualization
// Use band1 for red, band2 for green, 0 for blue
const band1 = image.select([exportBands[0]]).rename('vis_red');
const band2 = image.select([exportBands[1]]).rename('vis_green');
const zeros = ee.Image(0).rename('vis_blue');
previewImage = ee.Image.cat([band1, band2, zeros]);
} else {
// Single band - make grayscale
const band = image.select([exportBands[0]]).rename('vis_band');
previewImage = ee.Image.cat([band, band, band]);
}
const previewUrl = previewImage.getThumbURL({
dimensions: '512x512',
region: exportRegion,
format: 'png',
min: 0,
max: 3000
});
// Calculate approximate file size
const pixelCount = Math.ceil((Math.PI * 5000 * 5000) / (scale * scale)); // For 5km buffer
const bytesPerPixel = 4 * exportBands.length; // 4 bytes per band (float32)
const approximateSizeMB = Math.round((pixelCount * bytesPerPixel) / (1024 * 1024));
resolve({
// Full resolution GeoTIFF download
download: {
url: downloadUrl,
format: 'GeoTIFF',
description: 'Full resolution GeoTIFF file for GIS import',
fileName: `${fileName}.tif`,
approximateSizeMB: approximateSizeMB
},
// Quick preview thumbnail
thumbnail: {
url: previewUrl,
format: 'PNG',
description: 'Quick preview thumbnail (512x512 PNG)',
dimensions: '512x512'
},
// Export metadata
metadata: {
bands: exportBands,
bandCount: exportBands.length,
scale: scale,
crs: crs,
resolution: `${scale} meters per pixel`,
maxPixels: maxPixels
},
// Usage instructions
instructions: {
thumbnail: 'Open thumbnail.url in browser for quick preview',
download: 'Open download.url to download full GeoTIFF (may take time for large areas)',
gis: 'The downloaded GeoTIFF can be imported into ArcGIS, QGIS, or other GIS software'
}
});
} catch (error) {
reject(error);
}
});
}
/**
* Export to Google Drive (requires authentication)
* @param {object} params - Export parameters
* @returns {Promise<object>} Export task info
*/
async function exportToDrive(params) {
const ee = getEarthEngine();
const {
datasetId,
imageId,
startDate,
endDate,
region,
scale = 10,
folder = 'EarthEngine',
fileName = `export_${Date.now()}`,
bands = null,
maxPixels = 1e9
} = params;
return new Promise((resolve, reject) => {
try {
let image;
// Create composite if dataset info provided
if (datasetId && startDate && endDate) {
let collection = ee.ImageCollection(datasetId)
.filterDate(startDate, endDate);
if (region) {
const geometry = region.type === 'Point'
? ee.Geometry.Point(region.coordinates).buffer(5000)
: ee.Geometry.Polygon(region.coordinates);
collection = collection.filterBounds(geometry);
}
// Apply cloud masking for Sentinel-2
if (datasetId.includes('S2')) {
collection = collection.map(function(image) {
const qa = image.select('QA60');
const cloudBitMask = 1 << 10;
const cirrusBitMask = 1 << 11;
const mask = qa.bitwiseAnd(cloudBitMask).eq(0)
.and(qa.bitwiseAnd(cirrusBitMask).eq(0));
return image.updateMask(mask)
.select('B.*')
.copyProperties(image, ['system:time_start']);
});
}
image = collection.median();
if (bands && bands.length > 0) {
image = image.select(bands);
}
} else if (imageId) {
image = ee.Image(imageId);
if (bands && bands.length > 0) {
image = image.select(bands);
}
} else {
throw new Error('Either imageId or datasetId must be provided');
}
// Define export region
let exportRegion;
if (region) {
exportRegion = region.type === 'Point'
? ee.Geometry.Point(region.coordinates).buffer(5000)
: ee.Geometry.Polygon(region.coordinates);
} else {
exportRegion = image.geometry();
}
// Create export task
const task = ee.batch.Export.image.toDrive({
image: image,
description: fileName,
folder: folder,
fileNamePrefix: fileName,
region: exportRegion,
scale: scale,
maxPixels: maxPixels,
fileFormat: 'GeoTIFF'
});
// Start the task
task.start();
resolve({
taskId: task.id,
status: 'RUNNING',
fileName: `${fileName}.tif`,
folder: folder,
scale: scale,
description: 'Export task started. Check Google Drive for the file once complete.',
instructions: 'The file will appear in your Google Drive in the specified folder when ready.'
});
} catch (error) {
reject(error);
}
});
}
module.exports = {
exportToDownload,
exportToDrive
};
