cb.js

//VERSION=3

function setup() {
    return {
        input: ["B04", "B08", "dataMask"],
        output: [
            { id: "default", bands: 4 },
            { id: "index", bands: 1, sampleType: "FLOAT32" },
            { id: "eobrowserStats", bands: 1, sampleType: "FLOAT32" },
            { id: "dataMask", bands: 1 }
        ]
    };
}

const ramp = [
    [-0.5, [0.05, 0.05, 0.05]],
    [-0.2, [0.75, 0.75, 0.75]],
    [-0.1, [0.86, 0.86, 0.86]],
    [0, [0.92, 0.92, 0.92]],
    [0.025, [1, 0.98, 0.8]],
    [0.05, [0.93, 0.91, 0.71]],
    [0.075, [0.87, 0.85, 0.61]],
    [0.1, [0.8, 0.78, 0.51]],
    [0.125, [0.74, 0.72, 0.42]],
    [0.15, [0.69, 0.76, 0.38]],
    [0.175, [0.64, 0.8, 0.35]],
    [0.2, [0.57, 0.75, 0.32]],
    [0.25, [0.5, 0.7, 0.28]],
    [0.3, [0.44, 0.64, 0.25]],
    [0.35, [0.38, 0.59, 0.21]],
    [0.4, [0.31, 0.54, 0.18]],
    [0.45, [0.25, 0.49, 0.14]],
    [0.5, [0.19, 0.43, 0.11]],
    [0.55, [0.13, 0.38, 0.07]],
    [0.6, [0.06, 0.33, 0.04]],
    [1, 0, 0.27, 0],
];

const visualizer = new ColorRampVisualizer(ramp);

function evaluatePixel(samples) {
    let val = index(samples.B08, samples.B04);
    const imgVals = visualizer.process(val);
    // 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.
    const indexVal = samples.dataMask === 1 ? val : NaN;

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