@woosh/meep-engine/src/core/math/idct_2d.js

Pure JavaScript game engine. Fully featured and production ready.

import { idct_1d } from "./idct_1d.js";

/**
 * Performs a 2D 8x8 Inverse Discrete Cosine Transform.
 *
 * The 2D IDCT is computed by applying the 1D IDCT to each column
 * and then to each row of the 8x8 block.
 *
 * @param {Float64Array} block A pointer to a 64-element array (representing an 8x8 block)
 * of DCT coefficients. The transformation is done in-place.
 */
export function idct_2d(block) {
    // Pass 1: Apply 1D IDCT to each column
    for (let i = 0; i < 8; ++i) {
        idct_1d(block, i, 8);
    }

    // Pass 2: Apply 1D IDCT to each row
    for (let i = 0; i < 8; ++i) {
        idct_1d(block, i * 8, 1);
    }
}