function downScaleCanvas(a, b) {
    var c = Math.ceil,
        d = Math.floor;
    if (!(1 > b) || !(0 < b)) throw "scale must be a positive number <1 ";
    var e = b * b,
        f = a.width,
        g = a.height,
        h = d(f * b),
        i = d(g * b),
        j = 0,
        k = 0,
        l = 0,
        m = 0,
        n = 0,
        o = 0,
        p = 0,
        q = 0,
        r = 0,
        s = 0,
        t = 0,
        u = 0,
        v = 0,
        x = 0,
        y = 0,
        z = !1,
        A = !1,
        B = a.getContext("2d").getImageData(0, 0, f, g).data,
        C = new Float32Array(3 * h * i),
        D = 0,
        E = 0,
        F = 0;
    for (k = 0; k < g; k++)
        for (n = k * b, r = 0 | n, o = 3 * r * h, A = r != (0 | n + b), A && (x = r + 1 - n, y = n + b - r - 1), j = 0; j < f; j++, l += 4) m = j * b, q = 0 | m, p = o + 3 * q, z = q != (0 | m + b), z && (u = q + 1 - m, v = m + b - q - 1), D = B[l], E = B[l + 1], F = B[l + 2], z || A ? z && !A ? (s = u * b, C[p] += D * s, C[p + 1] += E * s, C[p + 2] += F * s, t = v * b, C[p + 3] += D * t, C[p + 4] += E * t, C[p + 5] += F * t) : A && !z ? (s = x * b, C[p] += D * s, C[p + 1] += E * s, C[p + 2] += F * s, t = y * b, C[p + 3 * h] += D * t, C[p + 3 * h + 1] += E * t, C[p + 3 * h + 2] += F * t) : (s = u * x, C[p] += D * s, C[p + 1] += E * s, C[p + 2] += F * s, t = v * x, C[p + 3] += D * t, C[p + 4] += E * t, C[p + 5] += F * t, t = u * y, C[p + 3 * h] += D * t, C[p + 3 * h + 1] += E * t, C[p + 3 * h + 2] += F * t, t = v * y, C[p + 3 * h + 3] += D * t, C[p + 3 * h + 4] += E * t, C[p + 3 * h + 5] += F * t) : (C[p] += D * e, C[p + 1] += E * e, C[p + 2] += F * e);
    var G = document.createElement("canvas");
    G.width = h, G.height = i;
    var H = G.getContext("2d"),
        I = H.getImageData(0, 0, h, i),
        J = I.data,
        K = 0;
    for (l = 0, p = 0; K < h * i; l += 3, p += 4, K++) J[p] = c(C[l]), J[p + 1] = c(C[l + 1]), J[p + 2] = c(C[l + 2]), J[p + 3] = 255;
    return H.putImageData(I, 0, 0), G
}