Function createColormap

stackgl_modules/index.js:9416–9523

(spec)

module.exports = createColormap;

function createColormap (spec) {
    /*
     * Default Options
     */
    var indicies, fromrgba, torgba,
        nsteps, cmap, colormap, format,
        nshades, colors, alpha, i;

    if ( !spec ) spec = {};

    nshades = (spec.nshades || 72) - 1;
    format = spec.format || 'hex';

    colormap = spec.colormap;
    if (!colormap) colormap = 'jet';

    if (typeof colormap === 'string') {
        colormap = colormap.toLowerCase();

        if (!colorScale[colormap]) {
            throw Error(colormap + ' not a supported colorscale');
        }

        cmap = colorScale[colormap];

    } else if (Array.isArray(colormap)) {
        cmap = colormap.slice();

    } else {
        throw Error('unsupported colormap option', colormap);
    }

    if (cmap.length > nshades + 1) {
        throw new Error(
            colormap+' map requires nshades to be at least size '+cmap.length
        );
    }

    if (!Array.isArray(spec.alpha)) {

        if (typeof spec.alpha === 'number') {
            alpha = [spec.alpha, spec.alpha];

        } else {
            alpha = [1, 1];
        }

    } else if (spec.alpha.length !== 2) {
        alpha = [1, 1];

    } else {
        alpha = spec.alpha.slice();
    }

    // map index points from 0..1 to 0..n-1
    indicies = cmap.map(function(c) {
        return Math.round(c.index * nshades);
    });