streamtools/resizer-xdrop9.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         void do_resize(uint8_t* target, uint32_t twidth, uint32_t theight,
  16                 const uint8_t* source, uint32_t swidth, uint32_t sheight)
  17         {
  18                 uint32_t* __restrict__ src = (uint32_t*)source;
  19                 uint32_t* __restrict__ dest = (uint32_t*)target;
  20                 uint32_t pwidth = swidth * 8 / 9 + swidth % 9;
  21
  22                 for(uint32_t y = 0; y < theight; y++)
  23                         for(uint32_t x = 0; x < twidth; x++) {
  24                                 uint32_t _x = nnscale(x, pwidth, twidth);
  25                                 uint32_t _y = nnscale(y, sheight, theight);
  26                                 _x = _x / 8 * 9 + _x % 8;
  27                                 dest[y * twidth + x] = src[_y * swidth + _x];
  28                         }
  29         }
  30
  31         simple_resizer factory("xdrop9", do_resize);
  32 }