streamtools/resizer-nearest.cpp

   1 #include "resize.hpp"
   2 #include <stdint.h>
   3 #include <cmath>
   4 #include <stdexcept>
   5
   6 namespace
   7 {
   8         inline uint32_t nnscale(uint32_t value, uint32_t trange, uint32_t srange)
   9         {
  10                 //x / trange is as good approximation for value / srange as possible.
  11                 //=> x is as good approximation for value * trange / srange as possible.
  12                 return (uint32_t)(((uint64_t)value * trange + srange / 2) / srange);
  13         }
  14
  15         class resizer_local : public resizer
  16         {
  17         public:
  18                 void operator()(uint8_t* target, uint32_t twidth, uint32_t theight,
  19                         const uint8_t* source, uint32_t swidth, uint32_t sheight)
  20                 {
  21                         uint32_t* __restrict__ src = (uint32_t*)source;
  22                         uint32_t* __restrict__ dest = (uint32_t*)target;
  23
  24                         for(uint32_t y = 0; y < theight; y++)
  25                                 for(uint32_t x = 0; x < twidth; x++) {
  26                                         uint32_t _x = nnscale(x, swidth, twidth);
  27                                         uint32_t _y = nnscale(y, sheight, theight);
  28                                         dest[y * twidth + x] = src[_y * swidth + _x];
  29                                 }
  30                 }
  31         };
  32
  33         class resizer_local_factory : public resizer_factory
  34         {
  35         public:
  36                 resizer_local_factory()
  37                         : resizer_factory("nearest")
  38                 {
  39                 }
  40
  41                 resizer& make(const std::string& type)
  42                 {
  43                         return *new resizer_local();
  44                 }
  45         } factory;
  46 }