/* Decoding of integer image samples to float image samples. */
/* Last edited on 2016-04-11 21:52:13 by stolfilocal */

#ifndef dsm_image_decoding_H
#define dsm_image_decoding_H

#define _GNU_SOURCE
#include <stdio.h>

/* PIXEL DECODING */
  
typedef struct dsm_image_decoding_t
  { double gamma; 
    double bias;
    double vlo; 
    double vhi;
  } dsm_image_decoding_t;
  /* Specifies a sample decoding function, that maps an integer sample {p}
    in the range {0..maxval} (such as read from an image file) 
    to a {float} value {v} in the range {[vlo_vhi]}.
    
    In particular, if {gamma} is 1.0, the {bias} is
    irrelevant, and the decoding is a linear map into {[vlo_vhi]}.
    
    More generally, the sample {p} is first mapped to a value {s} in the range {[0_1]}
    by the formula {s = (p+0.5)/(maxval=1)}. The value {s} is then mapped by shifting and scaling to a
    value {t} in a suitable interval {[tlo_thi]} contained in {[-1_+1]}.
    Then the non-linear mapping described in {sample_conv_gamma_INFO} is
    applied, with the given parameters {gamma} and {bias}, resuting in a
    value {u} that ranges in another interval {[ulo_uhi]} contained in
    {[-1_+1]}. Finally, {u} is multiplied by {fmax{fabs(vlo),fabs(vhi))}
    to give the final {v}.  The ends {tlo} and {thi} are chosen
    so that {v=0} would be obtained when {t=u=0}. 
    
    The same {dsm_image_decoding_t} record is used to specify
    the encoding of float values in the range {[vlo_vhi]} as
    integer sample values in the file. In that case, it 
    specifies the inverse of the function above, with 
    nearest-integer rounding in the last step.*/

void dsm_image_decoding_compute_linear_map(dsm_image_decoding_t *dec, int NC, double tlo[], double thi[]);
  /* Computes the range endpoints {tlo} and {thi} of the decoding
    algorithm above, with the parameters in {dec}. These values are
    replicated {NC} times in the given arrays.
    
    Once the integer samples have been mapped linearly to {[tlo_thi]},
    the non-linear gamma encoding can be applied. */

#endif