1 

     2 #include "tile.h"

     3 #include "render_struct.h"

     4 

     5 #define MIN(a, b) ((a) < (b) ? (a) : (b))

     6 #define MAX(a, b) ((a) > (b) ? (a) : (b))

     7 

     8 int render_set_tile (struct render *render_info, u_int32_t view_w, u_int32_t view_h, u_int32_t x, u_int32_t y, u_int16_t zoom) {

     9     // figure out how many tiles will fit onto the view area

    10     u_int16_t tiles = MIN(

    11         MAX(view_w / TILE_WIDTH, 1),

    12         MAX(view_h / TILE_HEIGHT, 1)

    13     ) + 1;

    14     

    15     // have it be square

    16     view_w = tiles * TILE_WIDTH;

    17     view_h = tiles * TILE_HEIGHT;

    18     

    19     // the image width is fixed

    20     render_info->img_w = TILE_WIDTH;

    21     render_info->img_h = TILE_HEIGHT;

    22     

    23     // calcuate how wide each pixel is

    24     double width_scale = REGION_W/(view_w << zoom);

    25     double height_scale = REGION_H/(view_h << zoom);

    26     

    27     // calcuate the region

    28     render_info->x1 = REGION_X1 + x * width_scale;

    29     render_info->y1 = REGION_Y1 + y * height_scale;

    30     render_info->x2 = render_info->x1 + TILE_WIDTH * width_scale;

    31     render_info->y2 = render_info->y1 + TILE_HEIGHT * height_scale;

    32     

    33     // ok

    34     return 0;

    35 }