Function bm_CreateChunkedBitmap

bitmap/bitmain.cpp:1421–1516

Given a bitmap handle, breaks a bitmap into smaller pieces. Note, this routine isn't terrible fast or efficient, and you must free the bitmaps returned to you in the bm_array

// Note, this routine isn't terrible fast or efficient, and you
// must free the bitmaps returned to you in the bm_array
bool bm_CreateChunkedBitmap(int bm_handle, chunked_bitmap *chunk) {
  int i;
  int *bm_array;
  int bw = bm_w(bm_handle, 0);
  int bh = bm_h(bm_handle, 0);
  // determine optimal size of the square bitmaps
  float fopt = 128.0f;
  int iopt;
  // find the smallest dimension and base off that
  int smallest = std::min(bw, bh);
  if (smallest <= 32)
    fopt = 32;
  else if (smallest <= 64)
    fopt = 64;
  else
    fopt = 128;
  iopt = (int)fopt;
  // Get how many pieces we need across and down
  float temp = bw / fopt;
  int how_many_across = temp;
  if ((temp - how_many_across) > 0)
    how_many_across++;
  temp = bh / fopt;
  int how_many_down = temp;
  if ((temp - how_many_down) > 0)
    how_many_down++;
  ASSERT(how_many_across > 0);
  ASSERT(how_many_down > 0);
  // Allocate memory to hold our list of pieces
  bm_array = (int *)mem_malloc(how_many_down * how_many_across * sizeof(int));
  ASSERT(bm_array);
  for (i = 0; i < how_many_down * how_many_across; i++) {
    bm_array[i] = bm_AllocBitmap(iopt, iopt, 0);
    ASSERT(bm_array[i] > -1);
    // Fill our new pieces with transparency
    bm_ClearBitmap(bm_array[i]);
  }
  // Now go through our big bitmap and partition it into pieces
  uint16_t *src_data = bm_data(bm_handle, 0);
  uint16_t *sdata;
  uint16_t *ddata;
  int shift;
  switch (iopt) {
  case 32:
    shift = 5;
    break;
  case 64:
    shift = 6;
    break;
  case 128:
    shift = 7;
    break;
  default:
    Int3(); // Get Jeff
    break;
  }
  int maxx, maxy;
  int windex, hindex;