/* See {dsm_image_decoding.h} */
/* Last edited on 2016-04-11 22:04:27 by stolfilocal */

#define _GNU_SOURCE
#include <stdio.h>
#include <math.h>
#include <assert.h>

#include <bool.h>
#include <affirm.h>

#include <sample_conv.h>
#include <dsm_image_decoding.h>

void dsm_image_decoding_compute_linear_map(dsm_image_decoding_t *dec, int NC, double tlo[], double thi[])
  {
    demand(! (isnan(dec->gamma) || isnan(dec->bias) || isnan(dec->vlo) || isnan(dec->vhi)), "undefined {dec}");
    double etlo, ethi;
    if (dec->gamma == 1.0)
      { /* Simple affine map: */
        etlo = (float)dec->vlo;
        ethi = (float)dec->vhi;
      }
    else
      { /* Must more complicated map: */
        double vmax = fmax(fabs(dec->vlo), fabs(dec->vhi));
        double ulo = dec->vlo/vmax;
        double uhi = dec->vhi/vmax;
        /* Must find {etlo,ethi} that are gamma mapped to {ulo,uhi}: */
        etlo = (double)sample_conv_gamma((float)ulo, 1/dec->gamma, dec->bias);
        ethi = (double)sample_conv_gamma((float)uhi, 1/dec->gamma, dec->bias);
      }
    /* Replicate into arrays: */
    for (int c = 0; c < NC; c++) { tlo[c] = etlo; thi[c] = ethi; }
  }