GEE: How to transform masked values (NODATA) to -9999?

Question

How can I transform NoData (masked) values to a value? When the image is mapped, there are a lot of values that are masked and I would like to get a value (-9999) on that masked pixels.

var region = geometry;


// Collect data and filter by total dates
var coll = ee.ImageCollection ("MODIS/006/MOD16A2")
.filterDate('2000-01-01', '2014-12-31')
.filterBounds(region)
.filter(ee.Filter.calendarRange(1,1,'month'));

print (coll)
var modisET = ee.Image('MODIS/006/MOD16A2/2001_01_01')
.select("ET");


var multiply = modisET.multiply(0.1)

var divide = multiply.divide(8)


// Normalize the image and add it to the map.
var rescaled = divide.unitScale(0,1);
var visParams = {min: -1, max: 1};


var reprojected = divide
    .unitScale(0, 1)
    .reproject('EPSG:4326', null, 500);

    Map.addLayer(reprojected)



// Export the image, specifying scale and region.
Export.image.toDrive({
  image: reprojected,
  description: '2001_01_01',
  scale: 500,
  region: table
});

Answer 1

This can be done using the unmask function on your image, which allows you to set a value of your choice for the masked pixels.

.unmask(-9999)

An example script building on your question: https://code.earthengine.google.com/87f1a9d5193c562ff016fd4b13c45720