medium_goes_functions.js

// Applies scaling factors.
var applyScaleAndOffset = function(img) {
  var getFactorImg = function(factorNames) {
    var factorList = img.toDictionary().select(factorNames).values();
    return ee.Image.constant(factorList);
  };
  var scaleImg = getFactorImg(['CMI_C.._scale']);
  var offsetImg = getFactorImg(['CMI_C.._offset']);
  var scaled = img.select('CMI_C..').multiply(scaleImg).add(offsetImg);
  return img.addBands({srcImg: scaled, overwrite: true});
};

// Adds a synthetic green band.
var addGreenBand = function(img) {
  var green = img.expression({
    expression: 'CMI_GREEN = 0.45 * red + 0.10 * nir + 0.45 * blue',
    map: {
      blue: img.select('CMI_C01'),
      red: img.select('CMI_C02'),
      nir: img.select('CMI_C03')
    }
  });
  return img.addBands(green);
};

// Scales select bands for visualization.
var scaleForVis = function(img) {
  return img.select(['CMI_C01', 'CMI_GREEN', 'CMI_C02', 'CMI_C03', 'CMI_C05'])
              .resample('bicubic')
              .log10()
              .interpolate([-1.6, 0.176], [0, 1], 'clamp')
              .unmask(0)
              .set('system:time_start', img.get('system:time_start'));
};

// Wraps previous functions.
var processForVis = function(img) {
  return scaleForVis(addGreenBand(applyScaleAndOffset(img)));
};