// File: crn_resample_filters.cpp
// RG: This is public domain code, originally derived from Graphics Gems 3, see: http://code.google.com/p/imageresampler/
#include "crn_core.h"
#include "crn_resample_filters.h"

namespace crnlib {
#define M_PI 3.14159265358979323846

// To add your own filter, insert the new function below and update the filter table.
// There is no need to make the filter function particularly fast, because it's
// only called during initializing to create the X and Y axis contributor tables.

#define BOX_FILTER_SUPPORT (0.5f)
static float box_filter(float t) /* pulse/Fourier window */
{
  // make_clist() calls the filter function with t inverted (pos = left, neg = right)
  if ((t >= -0.5f) && (t < 0.5f))
    return 1.0f;
  else
    return 0.0f;
}

#define TENT_FILTER_SUPPORT (1.0f)
static float tent_filter(float t) /* box (*) box, bilinear/triangle */
{
  if (t < 0.0f)
    t = -t;

  if (t < 1.0f)
    return 1.0f - t;
  else
    return 0.0f;
}

#define BELL_SUPPORT (1.5f)
static float bell_filter(float t) /* box (*) box (*) box */
{
  if (t < 0.0f)
    t = -t;

  if (t < .5f)
    return (.75f - (t * t));

  if (t < 1.5f) {
    t = (t - 1.5f);
    return (.5f * (t * t));
  }

  return (0.0f);
}

#define B_SPLINE_SUPPORT (2.0f)
static float B_spline_filter(float t) /* box (*) box (*) box (*) box */
{
  float tt;

  if (t < 0.0f)
    t = -t;

  if (t < 1.0f) {
    tt = t * t;
    return ((.5f * tt * t) - tt + (2.0f / 3.0f));
  } else if (t < 2.0f) {
    t = 2.0f - t;
    return ((1.0f / 6.0f) * (t * t * t));
  }

  return (0.0f);
}

// Dodgson, N., "Quadratic Interpolation for Image Resampling"
#define QUADRATIC_SUPPORT 1.5f
static float quadratic(float t, const float R) {
  if (t < 0.0f)
    t = -t;
  if (t < QUADRATIC_SUPPORT) {
    float tt = t * t;
    if (t <= .5f)
      return (-2.0f * R) * tt + .5f * (R + 1.0f);
    else
      return (R * tt) + (-2.0f * R - .5f) * t + (3.0f / 4.0f) * (R + 1.0f);
  } else
    return 0.0f;
}

static float quadratic_interp_filter(float t) {
  return quadratic(t, 1.0f);
}

static float quadratic_approx_filter(float t) {
  return quadratic(t, .5f);
}

static float quadratic_mix_filter(float t) {
  return quadratic(t, .8f);
}

// Mitchell, D. and A. Netravali, "Reconstruction Filters in Computer Graphics."
// Computer Graphics, Vol. 22, No. 4, pp. 221-228.
// (B, C)
// (1/3, 1/3)  - Defaults recommended by Mitchell and Netravali
// (1, 0)	   - Equivalent to the Cubic B-Spline
// (0, 0.5)		- Equivalent to the Catmull-Rom Spline
// (0, C)		- The family of Cardinal Cubic Splines
// (B, 0)		- Duff's tensioned B-Splines.
static float mitchell(float t, const float B, const float C) {
  float tt;

  tt = t * t;

  if (t < 0.0f)
    t = -t;

  if (t < 1.0f) {
    t = (((12.0f - 9.0f * B - 6.0f * C) * (t * tt)) + ((-18.0f + 12.0f * B + 6.0f * C) * tt) + (6.0f - 2.0f * B));

    return (t / 6.0f);
  } else if (t < 2.0f) {
    t = (((-1.0f * B - 6.0f * C) * (t * tt)) + ((6.0f * B + 30.0f * C) * tt) + ((-12.0f * B - 48.0f * C) * t) + (8.0f * B + 24.0f * C));

    return (t / 6.0f);
  }

  return (0.0f);
}

#define MITCHELL_SUPPORT (2.0f)
static float mitchell_filter(float t) {
  return mitchell(t, 1.0f / 3.0f, 1.0f / 3.0f);
}

#define CATMULL_ROM_SUPPORT (2.0f)
static float catmull_rom_filter(float t) {
  return mitchell(t, 0.0f, .5f);
}

static double sinc(double x) {
  x = (x * M_PI);

  if ((x < 0.01f) && (x > -0.01f))
    return 1.0f + x * x * (-1.0f / 6.0f + x * x * 1.0f / 120.0f);

  return sin(x) / x;
}

static float clean(double t) {
  const float EPSILON = .0000125f;
  if (fabs(t) < EPSILON)
    return 0.0f;
  return (float)t;
}

//static double blackman_window(double x)
//{
//	return .42f + .50f * cos(M_PI*x) + .08f * cos(2.0f*M_PI*x);
//}

static double blackman_exact_window(double x) {
  return 0.42659071f + 0.49656062f * cos(M_PI * x) + 0.07684867f * cos(2.0f * M_PI * x);
}

#define BLACKMAN_SUPPORT (3.0f)
static float blackman_filter(float t) {
  if (t < 0.0f)
    t = -t;

  if (t < 3.0f)
    //return clean(sinc(t) * blackman_window(t / 3.0f));
    return clean(sinc(t) * blackman_exact_window(t / 3.0f));
  else
    return (0.0f);
}

#define GAUSSIAN_SUPPORT (1.25f)
static float gaussian_filter(float t)  // with blackman window
{
  if (t < 0)
    t = -t;
  if (t < GAUSSIAN_SUPPORT)
    return clean(exp(-2.0f * t * t) * sqrt(2.0f / M_PI) * blackman_exact_window(t / GAUSSIAN_SUPPORT));
  else
    return 0.0f;
}

// Windowed sinc -- see "Jimm Blinn's Corner: Dirty Pixels" pg. 26.
#define LANCZOS3_SUPPORT (3.0f)
static float lanczos3_filter(float t) {
  if (t < 0.0f)
    t = -t;

  if (t < 3.0f)
    return clean(sinc(t) * sinc(t / 3.0f));
  else
    return (0.0f);
}

#define LANCZOS4_SUPPORT (4.0f)
static float lanczos4_filter(float t) {
  if (t < 0.0f)
    t = -t;

  if (t < 4.0f)
    return clean(sinc(t) * sinc(t / 4.0f));
  else
    return (0.0f);
}

#define LANCZOS6_SUPPORT (6.0f)
static float lanczos6_filter(float t) {
  if (t < 0.0f)
    t = -t;

  if (t < 6.0f)
    return clean(sinc(t) * sinc(t / 6.0f));
  else
    return (0.0f);
}

#define LANCZOS12_SUPPORT (12.0f)
static float lanczos12_filter(float t) {
  if (t < 0.0f)
    t = -t;

  if (t < 12.0f)
    return clean(sinc(t) * sinc(t / 12.0f));
  else
    return (0.0f);
}

static double bessel0(double x) {
  const double EPSILON_RATIO = 1E-16;
  double xh, sum, pow, ds;
  int k;

  xh = 0.5 * x;
  sum = 1.0;
  pow = 1.0;
  k = 0;
  ds = 1.0;
  while (ds > sum * EPSILON_RATIO)  // FIXME: Shouldn't this stop after X iterations for max. safety?
  {
    ++k;
    pow = pow * (xh / k);
    ds = pow * pow;
    sum = sum + ds;
  }

  return sum;
}

static const float KAISER_ALPHA = 4.0;
static double kaiser(double alpha, double half_width, double x) {
  const double ratio = (x / half_width);
  return bessel0(alpha * sqrt(1 - ratio * ratio)) / bessel0(alpha);
}

#define KAISER_SUPPORT 3
static float kaiser_filter(float t) {
  if (t < 0.0f)
    t = -t;

  if (t < KAISER_SUPPORT) {
    // db atten
    const float att = 40.0f;
    const float alpha = (float)(exp(log((double)0.58417 * (att - 20.96)) * 0.4) + 0.07886 * (att - 20.96));
    //const float alpha = KAISER_ALPHA;
    return (float)clean(sinc(t) * kaiser(alpha, KAISER_SUPPORT, t));
  }

  return 0.0f;
}

const resample_filter g_resample_filters[] =
    {
        {"box", box_filter, BOX_FILTER_SUPPORT},
        {"tent", tent_filter, TENT_FILTER_SUPPORT},
        {"bell", bell_filter, BELL_SUPPORT},
        {"b-spline", B_spline_filter, B_SPLINE_SUPPORT},
        {"mitchell", mitchell_filter, MITCHELL_SUPPORT},
        {"lanczos3", lanczos3_filter, LANCZOS3_SUPPORT},
        {"blackman", blackman_filter, BLACKMAN_SUPPORT},
        {"lanczos4", lanczos4_filter, LANCZOS4_SUPPORT},
        {"lanczos6", lanczos6_filter, LANCZOS6_SUPPORT},
        {"lanczos12", lanczos12_filter, LANCZOS12_SUPPORT},
        {"kaiser", kaiser_filter, KAISER_SUPPORT},
        {"gaussian", gaussian_filter, GAUSSIAN_SUPPORT},
        {"catmullrom", catmull_rom_filter, CATMULL_ROM_SUPPORT},
        {"quadratic_interp", quadratic_interp_filter, QUADRATIC_SUPPORT},
        {"quadratic_approx", quadratic_approx_filter, QUADRATIC_SUPPORT},
        {"quadratic_mix", quadratic_mix_filter, QUADRATIC_SUPPORT},
};

const int g_num_resample_filters = sizeof(g_resample_filters) / sizeof(g_resample_filters[0]);

int find_resample_filter(const char* pName) {
  for (int i = 0; i < g_num_resample_filters; i++)
    if (_stricmp(pName, g_resample_filters[i].name) == 0)
      return i;
  return cInvalidIndex;
}

}  // namespace crnlib
