Select which bands to view on COGs with multiple bands.

Channel mapping
100% © Data provided by the European Space Agency

COGs may have multiple bands. You can select which bands to view, and specify how to map them to regular R, G, B colors.

index.js
import { MapControls } from 'three/examples/jsm/controls/MapControls.js';

import Extent from '@giro3d/giro3d/core/geographic/Extent.js';
import CogSource from '@giro3d/giro3d/sources/CogSource.js';
import Instance from '@giro3d/giro3d/core/Instance.js';
import ColorLayer from '@giro3d/giro3d/core/layer/ColorLayer.js';
import Interpretation from '@giro3d/giro3d/core/layer/Interpretation.js';
import Map from '@giro3d/giro3d/entities/Map.js';
import Inspector from '@giro3d/giro3d/gui/Inspector.js';

Instance.registerCRS('EPSG:32611', '+proj=utm +zone=11 +datum=WGS84 +units=m +no_defs +type=crs');

// Define geographic extent: CRS, min/max X, min/max Y
const extent = new Extent('EPSG:32611', 666285, 668533.5, 3997174, 3998444);
const center = extent.centerAsVector3();

// `viewerDiv` will contain Giro3D' rendering area (the canvas element)
const viewerDiv = document.getElementById('viewerDiv');

// Instantiate Giro3D
const instance = new Instance(viewerDiv, {
    crs: extent.crs(),
    renderer: {
        clearColor: 0x0a3b59,
    },
});

// Instantiate the camera
instance.camera.camera3D.position.set(center.x, center.y, 2500);

// Instantiate the controls
const controls = new MapControls(instance.camera.camera3D, instance.domElement);
controls.enableDamping = true;
controls.dampingFactor = 0.2;
controls.target.set(center.x, center.y + 1, center.z);

instance.useTHREEControls(controls);

// Construct a map and add it to the instance
const map = new Map('planar', { extent });
instance.add(map);

const channels = [0, 1, 2];

function createLayer() {
    // Data coming from the same source as
    // https://openlayers.org/en/latest/examples/cog-math-multisource.html
    const source = new CogSource({
        url: 'https://3d.oslandia.com/cog_data/20200428_211318_ssc8d1_0017_pansharpened.cog.tif',
        crs: extent.crs(),
        channels,
    });
    return new ColorLayer({
        name: 'color-layer',
        source,
        extent,
        interpretation: Interpretation.CompressTo8Bit(0, 900),
    });
}

let layer = createLayer();
map.addLayer(layer);

function bindDropdown(id, action) {
    document.getElementById(id).addEventListener('change', e => {
        const value = parseInt(e.target.value, 10);
        action(value);
        map.removeLayer(layer, { disposeLayer: true });
        layer = createLayer();
        map.addLayer(layer);
    });
}

bindDropdown('r-channel', v => {
    channels[0] = v;
});
bindDropdown('g-channel', v => {
    channels[1] = v;
});
bindDropdown('b-channel', v => {
    channels[2] = v;
});

Inspector.attach(document.getElementById('panelDiv'), instance);
index.html
<!doctype html>
<html lang="en">
    <head>
        <title>COG image manipulation</title>
        <meta charset="UTF-8" />
        <meta name="name" content="cog_channel_mapping" />
        <meta name="description" content="Select which bands to view on COGs with multiple bands." />
        <meta name="viewport" content="width=device-width, initial-scale=1.0" />

        <link rel="icon" href="https://giro3d.org/images/favicon.svg" />
        <link href="https://giro3d.org/assets/bootstrap-custom.css" rel="stylesheet" />
        <script src="https://giro3d.org/assets/bootstrap.bundle.min.js"></script>
        <link
            rel="stylesheet"
            type="text/css"
            href="https://giro3d.org/latest/css/example.css"
        />

        
    </head>

    <body>
        <div id="viewerDiv" class="m-0 p-0 w-100 h-100"></div>
        <div id="panelDiv" class="position-absolute top-0 start-0 mh-100 overflow-auto"></div>

        <div class="side-pane-with-status-bar">
            <div class="card">
                <div class="card-header">Channel mapping</div>

                <div class="card-body">
                    <div class="input-group mb-3">
                        <label class="input-group-text" for="r-channel">R</label>
                        <select class="form-select" id="r-channel" autocomplete="off">
                            <option value="0" selected>Band 1</option>
                            <option value="1">Band 2</option>
                            <option value="2">Band 3</option>
                            <option value="3">Band 4</option>
                        </select>
                    </div>
                    <div class="input-group mb-3">
                        <label class="input-group-text" for="g-channel">G</label>
                        <select class="form-select" id="g-channel" autocomplete="off">
                            <option value="0">Band 1</option>
                            <option value="1" selected>Band 2</option>
                            <option value="2">Band 3</option>
                            <option value="3">Band 4</option>
                        </select>
                    </div>
                    <div class="input-group mb-3">
                        <label class="input-group-text" for="b-channel" autocomplete="off">B</label>
                        <select class="form-select" id="b-channel">
                            <option value="0" selected>Band 1</option>
                            <option value="1">Band 2</option>
                            <option value="2" selected>Band 3</option>
                            <option value="3">Band 4</option>
                        </select>
                    </div>
                </div>
            </div>
        </div>

        <script type="module" src="index.js"></script>
        <script>
            /* activate popovers */
            const popoverTriggerList = [].slice.call(
                document.querySelectorAll('[data-bs-toggle="popover"]'),
            );
            popoverTriggerList.map(
                // bootstrap is used as script in the template, disable warning about undef
                // eslint-disable-next-line no-undef
                popoverTriggerEl =>
                    new bootstrap.Popover(popoverTriggerEl, {
                        trigger: 'hover',
                        placement: 'left',
                        content: document.getElementById(
                            popoverTriggerEl.getAttribute('data-bs-content'),
                        ).innerHTML,
                        html: true,
                    }),
            );
        </script>
    </body>
</html>
package.json
{
    "name": "cog_channel_mapping",
    "dependencies": {
        "@giro3d/giro3d": "0.37.2"
    },
    "devDependencies": {
        "vite": "^3.2.3"
    },
    "scripts": {
        "start": "vite",
        "build": "vite build"
    }
}