Method merge

src/laybasic/laybasic/layBitmap.cc:176–278

}

void 
Bitmap::merge (const lay::Bitmap *from, int dx, int dy)
{
  if (! from) {
    return;
  }
  if (dx >= int (width ()) || dy >= int (height ())) {
    return;
  }

  unsigned int from_height = from->height ();
  if (int (from_height) + dy > int (height ())) {
    from_height = height () - dy;
  }

  unsigned int n0 = 0;
  if (dy < 0) {
    if (dy + int (from_height) <= 0) {
      return;
    }
    n0 = (unsigned int) -dy;
  }

  unsigned int from_width = from->width ();
  if (int (from_width) + dx > int (width ())) {
    from_width = width () - dx;
  }

  if (dx < 0) {

    if (dx + int (from_width) <= 0) {
      return;
    }

    unsigned int mo = ((unsigned int) -dx) / 32;
    unsigned int m = (from_width + 31) / 32 - mo;
    unsigned int mm = (from_width + dx + 31) / 32;

    unsigned int s1 = ((unsigned int) -dx) % 32;
    unsigned int s2 = 32 - s1;

    for (unsigned int n = n0; n < from_height; ++n) {

      if (from->is_scanline_empty (n)) {
        continue;
      }

      const uint32_t *sl_from = from->scanline (n) + mo;
      uint32_t *sl_to = scanline (n + dy);

      if (! s1) {
        for (unsigned int i = 0; i < m; ++i) {
          *sl_to++ |= *sl_from++;
        }
      } else if (m) {
        for (unsigned int i = 1; i < m; ++i) {
          *sl_to++ |= (sl_from[1] << s2) | (sl_from[0] >> s1);
          ++sl_from;