static int16_t *precalc_coefs(double dist25, int depth) { int i; double gamma, simil, C; int16_t *ct = av_malloc((512<<LUT_BITS)*sizeof(int16_t)); if (!ct) return NULL; gamma = log(0.25) / log(1.0 - FFMIN(dist25,252.0)/255.0 - 0.00001); for (i = -255<<LUT_BITS; i <= 255<<LUT_BITS; i++) { double f = ((i<<(9-LUT_BITS)) + (1<<(8-LUT_BITS)) - 1) / 512.0; // midpoint of the bin simil = 1.0 - FFABS(f) / 255.0; C = pow(simil, gamma) * 256.0 * f; ct[(256<<LUT_BITS)+i] = lrint(C); } ct[0] = !!dist25; return ct; }