// resampler.h, Separable filtering image rescaler v2.21, Rich Geldreich - richgel99@gmail.com
// See unlicense.org text at the bottom of this file.
#ifndef __RESAMPLER_H__
#define __RESAMPLER_H__

#define RESAMPLER_DEBUG_OPS 0
#define RESAMPLER_DEFAULT_FILTER "lanczos4"

#define RESAMPLER_MAX_DIMENSION 16384

// float or double
typedef float Resample_Real;

class Resampler
{
public:
   typedef Resample_Real Sample;

   struct Contrib
   {
      Resample_Real weight;
      unsigned short pixel;
   };

   struct Contrib_List
   {
      unsigned short n;
      Contrib* p;
   };

   enum Boundary_Op
   {
      BOUNDARY_WRAP = 0,
      BOUNDARY_REFLECT = 1,
      BOUNDARY_CLAMP = 2
   };

   enum Status
   {
      STATUS_OKAY = 0,
      STATUS_OUT_OF_MEMORY = 1,
      STATUS_BAD_FILTER_NAME = 2,
      STATUS_SCAN_BUFFER_FULL = 3
   };
   
   // src_x/src_y - Input dimensions
   // dst_x/dst_y - Output dimensions
   // boundary_op - How to sample pixels near the image boundaries
   // sample_low/sample_high - Clamp output samples to specified range, or disable clamping if sample_low >= sample_high
   // Pclist_x/Pclist_y - Optional pointers to contributor lists from another instance of a Resampler
   // src_x_ofs/src_y_ofs - Offset input image by specified amount (fractional values okay)
   Resampler(
      int src_x, int src_y,
      int dst_x, int dst_y,
      Boundary_Op boundary_op = BOUNDARY_CLAMP,
      Resample_Real sample_low = 0.0f, Resample_Real sample_high = 0.0f,		
      const char* Pfilter_name = RESAMPLER_DEFAULT_FILTER,
      Contrib_List* Pclist_x = NULL,
      Contrib_List* Pclist_y = NULL,
      Resample_Real filter_x_scale = 1.0f,
      Resample_Real filter_y_scale = 1.0f,
      Resample_Real src_x_ofs = 0.0f, 
      Resample_Real src_y_ofs = 0.0f);

   ~Resampler();

   // Reinits resampler so it can handle another frame.
   void restart();

   // false on out of memory.
   bool put_line(const Sample* Psrc);

   // NULL if no scanlines are currently available (give the resampler more scanlines!)
   const Sample* get_line();

   Status status() const { return m_status; }

   // Returned contributor lists can be shared with another Resampler. 
   void get_clists(Contrib_List** ptr_clist_x, Contrib_List** ptr_clist_y);
   Contrib_List* get_clist_x() const {	return m_Pclist_x; }
   Contrib_List* get_clist_y() const {	return m_Pclist_y; }

   // Filter accessors.
   static int get_filter_num();
   static char* get_filter_name(int filter_num);
   
private:
   Resampler();
   Resampler(const Resampler& o);
   Resampler& operator= (const Resampler& o);

#ifdef RESAMPLER_DEBUG_OPS
   int total_ops;
#endif

   int m_intermediate_x;

   int m_resample_src_x;
   int m_resample_src_y;
   int m_resample_dst_x;
   int m_resample_dst_y;

   Boundary_Op m_boundary_op;

   Sample* m_Pdst_buf;
   Sample* m_Ptmp_buf;

   Contrib_List* m_Pclist_x;
   Contrib_List* m_Pclist_y;

   bool m_clist_x_forced;
   bool m_clist_y_forced;

   bool m_delay_x_resample;

   int* m_Psrc_y_count;
   unsigned char* m_Psrc_y_flag;

   // The maximum number of scanlines that can be buffered at one time.
   enum { MAX_SCAN_BUF_SIZE = RESAMPLER_MAX_DIMENSION };
   
   struct Scan_Buf
   {
      int scan_buf_y[MAX_SCAN_BUF_SIZE];
      Sample* scan_buf_l[MAX_SCAN_BUF_SIZE];
   };

   Scan_Buf* m_Pscan_buf;

   int m_cur_src_y;
   int m_cur_dst_y;

   Status m_status;

   void resample_x(Sample* Pdst, const Sample* Psrc);
   void scale_y_mov(Sample* Ptmp, const Sample* Psrc, Resample_Real weight, int dst_x);
   void scale_y_add(Sample* Ptmp, const Sample* Psrc, Resample_Real weight, int dst_x);
   void clamp(Sample* Pdst, int n);
   void resample_y(Sample* Pdst);

   int reflect(const int j, const int src_x, const Boundary_Op boundary_op);

   Contrib_List* make_clist(
      int src_x, int dst_x, Boundary_Op boundary_op,
      Resample_Real (*Pfilter)(Resample_Real),
      Resample_Real filter_support,
      Resample_Real filter_scale,
      Resample_Real src_ofs);

   inline int count_ops(Contrib_List* Pclist, int k)
   {
      int i, t = 0;
      for (i = 0; i < k; i++)
         t += Pclist[i].n;
      return (t);
   }

   Resample_Real m_lo;
   Resample_Real m_hi;

   inline Resample_Real clamp_sample(Resample_Real f) const
   {
      if (f < m_lo)
         f = m_lo;
      else if (f > m_hi)
         f = m_hi;
      return f;
   }   
};

#endif // __RESAMPLER_H__

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