/** Weighted per-channel variance of the box. It's used to decide which channel to split by */
static f_pixel box_variance(const hist_item achv[], const struct box *box)
{
f_pixel mean = box->color;
double variancea=0, variancer=0, varianceg=0, varianceb=0;
for(unsigned int i = 0; i < box->colors; ++i) {
f_pixel px = achv[box->ind + i].acolor;
double weight = achv[box->ind + i].adjusted_weight;
variancea += variance_diff(mean.a - px.a, 2.0/256.0)*weight;
variancer += variance_diff(mean.r - px.r, 1.0/256.0)*weight;
varianceg += variance_diff(mean.g - px.g, 1.0/256.0)*weight;
varianceb += variance_diff(mean.b - px.b, 1.0/256.0)*weight;
}
return (f_pixel){
.a = variancea*(4.0/16.0),
.r = variancer*(7.0/16.0),
.g = varianceg*(9.0/16.0),
.b = varianceb*(5.0/16.0),
};
}
static double box_max_error(const hist_item achv[], const struct box *box)
{
f_pixel mean = box->color;
double max_error = 0;
for(unsigned int i = 0; i < box->colors; ++i) {
const double diff = colordifference(mean, achv[box->ind + i].acolor);
if (diff > max_error) {
max_error = diff;
}
}
return max_error;
}
/** Weighted per-channel variance of the box. It's used to decide which channel to split by */
static f_pixel box_variance(const hist_item achv[], const struct box *box)
{
const f_pixel mean = box->color;
register double variancea=0, variancer=0, varianceg=0, varianceb=0;
f_pixel px_ret;
unsigned int i;
for(i = 0; i < box->colors; ++i) {
f_pixel px = achv[box->ind + i].acolor;
const double weight = achv[box->ind + i].adjusted_weight;
variancea += variance_diff(mean.a - px.a, 2.0/256.0)*weight;
variancer += variance_diff(mean.r - px.r, 1.0/256.0)*weight;
varianceg += variance_diff(mean.g - px.g, 1.0/256.0)*weight;
varianceb += variance_diff(mean.b - px.b, 1.0/256.0)*weight;
}
px_ret.a = variancea*(4.0/16.0);
px_ret.r = variancer*(7.0/16.0);
px_ret.g = varianceg*(9.0/16.0);
px_ret.b = varianceb*(5.0/16.0);
return px_ret;
}
