EE:A region must be a GeoJSON Polygon or LinearRing. Got: 'MultiPolygon'

Question

Tried to export transition classes for a region of interest. I cant export image to drive for my selected feature collection. Getting an error after running for a while,"A region must be a GeoJSON Polygon or LinearRing. Got: 'MultiPolygon'. Here is the code below- how can i export image for a region that i selected from my shapefiles?

var reg = ee.FeatureCollection('users/karmakersourav/shape')
    .filter(ee.Filter.eq('NAME_1', 'Chittagong'));

Map.addLayer(reg);

var gsw = ee.Image('JRC/GSW1_0/GlobalSurfaceWater');    
var transition = gsw.select('transition');    
Map.addLayer({      
eeObject: transition,
  name: 'Transition classes (2010-2015)',    
});

Export.image.toDrive({
 image: gsw,
 description: 'imageToCOGeoTiffExample',
 scale: 30,
 region: reg,
 fileFormat: 'GeoTIFF',
 maxPixels: 1e12,
 formatOptions: {
    cloudOptimized: true
  }
});

Answer 1

What you probably want to do is only export that part of the image which falls inside your region of interest, a featureCollection consisting of one feature which geometry is a multipolygon.

For that you'd best clip the image on your multipolygon, and then export that part of the image which falls inside the bounding rectangle of those polygons.

To get the bounding rectangle of your area of interest:

var reg = ee.FeatureCollection('users/karmakersourav/shape')
    .filter(ee.Filter.eq('NAME_1', 'Chittagong'));
// make one feature of the feature collection (as it only consists of 1 feature)
var reg = ee.Feature(reg.first());
// get the bounding rectangle of the feature collection
var boundingRectangle = reg.bounds();

Then clip your image on the geometry you have defined as input:

// load the image
var gsw = ee.Image('JRC/GSW1_0/GlobalSurfaceWater');    
var transition = gsw.select('transition');    
// clip the image to the region of interest to only export that part
var clipped = transition.clip(reg);

And then export the image using:

Export.image.toDrive({
image: clipped,
description: 'imageToCOGeoTiffExample',
scale: 30,
region: boundingRectangle,
fileFormat: 'GeoTIFF',
maxPixels: 1e12,
formatOptions: {
    cloudOptimized: true
  },
skipEmptyTiles: true
});

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