Export images in google earth engine with date name

Question

I would like to export the NDVI with the date in the filename. Now I can only export them with a list of numbers, e.g. example NDVI_1, NDVI_2 (as in the code that I show below) ... and I want it so NDVI_18042018.

// Load a FeatureCollection 
var violada = ee.FeatureCollection("ft:1KmH70D7VKdiWocelf0RtbL_kQhGk0LGkQQ7O-ceG");

// Load a FeatureCollection Sentinel 2.
var s2 = ee.ImageCollection('COPERNICUS/S2')
      .filterBounds(violada)
      .filterDate('2016-10-01', '2017-09-30');
print(s2);

// Function to mask clouds using the Sentinel-2 QA band..
function maskS2clouds(image) {
         var qa = image.select('QA60');
 // Bits 10 and 11 are clouds and cirrus, respectively.
         var cloudBitMask = ee.Number(2).pow(10).int();
         var cirrusBitMask = ee.Number(2).pow(11).int();
 // Both flags should be set to zero, indicating clear conditions.
         var mask = qa.bitwiseAnd(cloudBitMask).eq(0).and(
         qa.bitwiseAnd(cirrusBitMask).eq(0));
// Return the masked and scaled data.
   return image.updateMask(mask).divide(10000);
}
   var imagen=s2.map(maskS2clouds);

// visualize the first image in the collection, pre- and post- mask
var visParams = {bands: ['B8','B4','B3']}
Map.addLayer(ee.Image(imagen.first()), visParams, 'clouds masked', false)
Map.addLayer(ee.Image(s2.first()), visParams, 'original', false)

//add ndwi
var addNDVI = function(image) {
  return image.addBands(image.normalizedDifference(['B8','B4']).rename('NDVI'));
};
var imagen2=imagen.map(addNDVI);
var NDVI = imagen2.select(['NDVI']);
print(ee.Image(NDVI.first()));
var composite = NDVI.qualityMosaic('NDVI').clip(violada);
print(composite);

// Visualize NDVI
var ndviPalette = ['FFFFFF', 'CE7E45', 'DF923D', 'F1B555', 'FCD163',   '99B718',
  '74A901', '66A000', '529400', '3E8601', '207401', '056201',
  '004C00', '023B01', '012E01', '011D01', '011301'];
Map.addLayer(composite.select('NDVI'),
             {min:-1, max: 1, palette: ndviPalette}, 'ndvi');
//List NDVI
var list=NDVI.toList(150);
for (var i=0;i<150;i++){
     var image=ee.Image(list.get(i));
     var name=ee.String('NDVI_')
                .cat(ee.String(ee.Number(i)))
                .getInfo();
     print(name);
// Export NDVI        
     Export.image.toDrive({ 
           image: image,
           description:name,
           scale: 10,
           region:violada,
           crs : 'EPSG:32630'
           });
}
Map.setCenter(-0.6, 42, 12);

Google earth engine code is: https://code.earthengine.google.com/7101729aaaf2f8be4a0114561b9a673e

Answer 1

From the official Documentation:

Export.image.toDrive(image, description, folder, fileNamePrefix, dimensions, region, scale, crs, crsTransform, maxPixels, shardSize, fileDimensions, skipEmptyTiles)

Creates a batch task to export an Image as a raster to Drive. Tasks can be started from the Tasks tab. "crsTransform", "scale", and "dimensions" are mutually exclusive.

Arguments: image (Image): The image to export.

description (String, optional): A human-readable name of the task. Defaults to "myExportImageTask".

folder (String, optional): The Google Drive Folder that the export will reside in.

fileNamePrefix (String, optional): The Google Drive filename for the export. Defaults to the description.*

What you want is fileNamePrefix. So:

// Load a FeatureCollection 
var violada = ee.FeatureCollection("ft:1KmH70D7VKdiWocelf0RtbL_kQhGk0LGkQQ7O-ceG");

// Load a FeatureCollection Sentinel 2.
var s2 = ee.ImageCollection('COPERNICUS/S2')
          .filterBounds(violada)
          .filterDate('2016-10-01', '2017-09-30');
print(s2);

// Function to mask clouds using the Sentinel-2 QA band..
function maskS2clouds(image) {
  // get date of the image to pass it through
  var date = image.date().millis()
  var qa = image.select('QA60');

  // Bits 10 and 11 are clouds and cirrus, respectively.
  var cloudBitMask = ee.Number(2).pow(10).int();
  var cirrusBitMask = ee.Number(2).pow(11).int();

  // Both flags should be set to zero, indicating clear conditions.
  var mask = qa.bitwiseAnd(cloudBitMask).eq(0).and(
             qa.bitwiseAnd(cirrusBitMask).eq(0));

  // Return the masked and scaled data.
  return image.updateMask(mask).divide(10000).set('system:time_start', date);
}
var imagen=s2.map(maskS2clouds);

print(ee.Image(imagen.first()))

// visualize the first image in the collection, pre- and post- mask
var visParams = {bands: ['B8','B4','B3']}
Map.addLayer(ee.Image(imagen.first()), visParams, 'clouds masked', false)
Map.addLayer(ee.Image(s2.first()), visParams, 'original', false)

//add ndwi
var addNDVI = function(image) {
  return image.addBands(image.normalizedDifference(['B8','B4']).rename('NDVI'));
};
var imagen2=imagen.map(addNDVI);

var NDVI = imagen2//.select(['NDVI']);
print(ee.Image(NDVI.first()));

var composite = NDVI.qualityMosaic('NDVI').clip(violada);
print(composite);

// Visualize NDVI
var ndviPalette = ['FFFFFF', 'CE7E45', 'DF923D', 'F1B555', 'FCD163', '99B718',
  '74A901', '66A000', '529400', '3E8601', '207401', '056201',
  '004C00', '023B01', '012E01', '011D01', '011301'];
Map.addLayer(composite.select('NDVI'),
            {min:0, max: 1, palette: ndviPalette}, 'ndvi');
            

//List NDVI
var list=NDVI.toList(150);
    for (var i=0;i<150;i++){
         var image=ee.Image(list.get(i));
         var date = image.date().format('yyyy-MM-dd').getInfo()
         var name= 'NDVI_'+i.toString()+'_'+date
         print(name);
    // Export NDVI        
         Export.image.toDrive({ 
               image: image,
               description: name,
               fileNamePrefix: name,
               scale: 10,
               region:violada,
               crs : 'EPSG:32630'
               });
    }
Map.setCenter(-0.6, 42, 12);

Answer 2

You may want to fiddle with the date format. And you're going to have to getInfo() on this as you've done in your example:

var s2 = ee.ImageCollection('COPERNICUS/S2');
var first = ee.Image(s2.first());
var date = first.date();
var formatted = date.format('YYYYMMdd');