Get ndvi value when hovering mouse over pixel

[fellipe (Fellipe Ribeiro)]

Hello everyone, currently I have this script on a WMS layer:

//VERSION=3
function setup() {
  return {
    input: ["B03", "B04", "B08", "dataMask"],
    output: [
      { id: "default", bands: 4 },
      { id: "index", bands: 1, sampleType: "FLOAT32" },
      { id: "eobrowserStats", bands: 2, sampleType: 'FLOAT32' },
      { id: "dataMask", bands: 1 }
    ]
  };
}

const ramp = [
  [-0.5, 0x0c0c0c],
  [-0.2, 0xbfbfbf],
  [-0.1, 0xdbdbdb],
  [0, 0xeaeaea],
  [0.025, 0xfff9cc],
  [0.05, 0xede8b5],
  [0.075, 0xddd89b],
  [0.1, 0xccc682],
  [0.125, 0xbcb76b],
  [0.15, 0xafc160],
  [0.175, 0xa3cc59],
  [0.2, 0x91bf51],
  [0.25, 0x7fb247],
  [0.3, 0x70a33f],
  [0.35, 0x609635],
  [0.4, 0x4f892d],
  [0.45, 0x3f7c23],
  [0.5, 0x306d1c],
  [0.55, 0x216011],
  [0.6, 0x0f540a],
  [1, 0x004400],
];

const visualizer = new ColorRampVisualizer(ramp);

function evaluatePixel(samples) {
  let val = index(samples.B08, samples.B04);
  // The library for tiffs works well only if there is only one channel returned.
  // So we encode the "no data" as NaN here and ignore NaNs on frontend.

  // TODO: CHECK IF THIS indexVal IS STILL NECESSARY
  const indexVal = samples.dataMask === 1 ? val : NaN;
  const imgVals = visualizer.process(val);

  return {
    default: imgVals.concat(samples.dataMask),
    index: [indexVal],
    eobrowserStats: [val, isCloud(samples) ? 1 : 0],
    dataMask: [samples.dataMask]
  };
}

function isCloud(samples) {
  const NGDR = index(samples.B03, samples.B04);
  const bRatio = (samples.B03 - 0.175) / (0.39 - 0.175);
  return bRatio > 1 || (bRatio > 0 && NGDR > 0);
}

And what i want to do is something similar to this in my frontend:

But currently I can only get the rgb values when hovering:

so my question is, is there a way to me to compare the rgb to the a value that corresponds to a ndvi scale? by the way, i am using mapbox to show the maps

[chung.horng (Chung)]

Hi @fellipe ,

Please have a look at the How to get NDVI index value of the pixel thread.