// カーネル（3×3）
const kernel = [
    [1, 2, 1],
    [2, 4, 2],
    [1, 2, 1]
];
const kernelSum = 16;

// ぼかし処理
for (let y = 1; y < h - 1; y++) {
    for (let x = 1; x < w - 1; x++) {
        let sum = 0;
        for (let ky = -1; ky <= 1; ky++) {
            for (let kx = -1; kx <= 1; kx++) {
                sum += gray[(y + ky) * w + (x + kx)] * kernel[ky + 1][kx + 1];
            }
        }
        blurred[y * w + x] = sum / kernelSum;
    }
}