sImLib/img_path.hh

   1 #ifndef _SIMLIB_IMGPATH_HH
   2 #define _SIMLIB_IMGPATH_HH
   3
   4 #include <algorithm>
   5 #include <cstdlib>
   6
   7 /*
   8  * Walking macros from this file are adapted from CImg drawing
   9  * methods.
  10  */
  11
  12 // FIXME: width cropping does not work !?
  13
  14 /*
  15  * forline:
  16  *
  17  * Run body_code over all pixels of the (x0,y0)-(x1,y1) line.
  18  *
  19  * Demo example:
  20  *  sImLib_forline(img, x, y, ptrd,
  21  *                 0, 0, img.width, img.height,
  22  *                 if (x%2)
  23  *                   *ptrd = blue[k];
  24  *                 else
  25  *                   *ptrd = red[k];
  26  *                 printf("%d,%d ", x, y);
  27  *                 );
  28  */
  29 #define sImLib_forline(img,ptrd,x0,y0,x1,y1,body_code)                  \
  30   do {                                                                  \
  31     int nx0 = (x0), nx1 = (x1), ny0 = (y0), ny1 = (y1);                 \
  32                                                                         \
  33     if (nx0>nx1) { std::swap(nx0,nx1); std::swap(ny0,ny1); }            \
  34     if (nx1<0 || nx0>=(int)(img)->width) break;                         \
  35     if (nx0<0) { ny0-=nx0*(ny1-ny0)/(nx1-nx0); nx0=0; }                 \
  36     if (nx1>=(int)(img)->width)                                         \
  37       { ny1+=(nx1-(img)->width)*(ny0-ny1)/(nx1-nx0); nx1=(img)->width-1;} \
  38     if (ny0>ny1) { std::swap(nx0,nx1); std::swap(ny0,ny1); }            \
  39     if (ny1<0 || ny0>=(int)(img)->height) break;                        \
  40     if (ny0<0) { nx0-=ny0*(nx1-nx0)/(ny1-ny0); ny0=0; }                 \
  41     if (ny1>=(int)(img)->height)                                        \
  42       { nx1+=(ny1-(img)->height)*(nx0-nx1)/(ny1-ny0); ny1=(img)->height-1;} \
  43                                                                         \
  44     const bool steep = (ny1-ny0)>std::abs(nx1-nx0);                     \
  45     if (steep)   { std::swap(nx0,ny0); std::swap(nx1,ny1); }            \
  46     if (nx0>nx1) { std::swap(nx0,nx1); std::swap(ny0,ny1); }            \
  47     const int                                                           \
  48       dx = nx1-nx0, dy = std::abs(ny1-ny0),                             \
  49       offx = steep?(img)->width:1,                                      \
  50       offy = (ny0<ny1?1:-1)*(steep?1:(img)->width);                     \
  51                                                                         \
  52     sImLib::pixel *ptrd = steep?(img)->ptr(ny0,nx0):(img)->ptr(nx0,ny0); \
  53     for (int error=0, _x=nx0, linechange=0;                             \
  54          _x <= nx1;                                                     \
  55          _x++, linechange=(((error+=dy)<<1)>=dx),                       \
  56            ptrd+=offx, ptrd+=offy*linechange, error-=dx*linechange)     \
  57       do { body_code; } while(0);                                       \
  58   } while(0)
  59
  60 #endif // _SIMLIB_IMGPATH_HH