@4bitlabs/dct/dist/dct-n.js

Discrete cosine transform algorithms in js and ts

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.createDctOfN = createDctOfN;
function createDctOfN(N) {
    const COS = new Float64Array(N * N).map((_, i) => {
        const k = Math.floor(i / N);
        const n = i % N;
        return Math.cos((Math.PI * (n + 0.5) * k) / N);
    });
    const sqrt2_n = Math.sqrt(2 / N);
    function transform(vIn, vOut) {
        let sum;
        for (let k = 0; k < N; k++) {
            sum = 0;
            for (let n = 0; n < N; n++) {
                sum += vIn[n] * COS[n + k * N];
            }
            const s = k === 0 ? 1 / Math.SQRT2 : 1;
            vOut[k] = s * sqrt2_n * sum;
        }
    }
    function inverse(vIn, vOut) {
        let sum;
        for (let n = 0; n < N; n++) {
            sum = 0;
            for (let k = 0; k < N; k++) {
                const s = k === 0 ? Math.SQRT1_2 : 1;
                sum += s * vIn[k] * COS[n + k * N];
            }
            vOut[n] = sqrt2_n * sum;
        }
    }
    return { transform, inverse };
}
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