Re: [PATCH 0/2] MR8640: d2d1: Implement D2D1ComputeMaximumScaleFactor().

[Nikolay Sivov (＠nsivov)]

Nikolay Sivov (@nsivov) commented about dlls/d2d1/factory.c:
> - float a1, a2, c, e;
> -
> - TRACE("mat %p stub.\n", mat);
> -
> - /* 2x2 matrix, _31 and _32 are ignored. */
> - a1 = m[0][0] * m[0][0] + m[1][0] * m[1][0];
> - a2 = m[0][1] * m[0][1] + m[1][1] * m[1][1];
> - c = m[0][0] * m[0][1] + m[1][0] * m[1][1];
> -
> - /* Maximum scale factor equals to the maximum of the singular values s1, s2 of the matrix M
> -
> - s_i^2 = e_i where e_i (e1, e2) are eugenvalues of (transpose(M) * M)
> -
> - e1 + e2 = trace(transpose(M) * M) = a1 + a2
> -
> - e1 * e2 = det(transpose(M) * M) = a1 * a2 - c ^ 2. */
> -
> - e = a1 + a2 + sqrtf((a1 - a2) * (a1 - a2) + 4 * c * c);
> - return sqrtf(0.5f * e);

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