/* maskedLine 1.0, by Stijn 
   http://www.jazz2online.com/snippets/145/maskedline/ */

/*
 * Check whether any pixel on a line between two positions is masked
 *
 * Returns true if masked pixel is found, false if not.
 */
bool maskedLine(int x0, int y0, int x1, int y1, int layer = 4) {
  int x2;
  int y2;
  
  //straight lines
  if(x0 == x1 || y0 == y1) {
    if(y0 == y1) {
      if(x0 > x1) {
        x2 = x1; x1 = x0; x0 = x2; //swap
      }
      for(int x = x0; x < x1; x += 1) {
		    if(jjLayers[layer].maskedPixel(x, y0)) {
		      return true;
		    }
      }
      return false;
    }

		if (y0 > y1) {
      y2 = y1; y1 = y0; y0 = y2; //swap
		}
		
		for(int y = y0; y < y1; y += 1) {
		  if(jjLayers[layer].maskedPixel(x0, y)) {
		    return true;
		  }
    }
		return true;
	}
	
	
	//sloped lines
	bool steep = (abs(y1 - y0) > abs(x1 - x0));

	if (steep) {
    x2 = x0; x0 = y0; y0 = x2; //swap
    y2 = x1; x1 = y1; y1 = y2; //swap
  }

	if (x0 > x1) {
    x2 = x1; x1 = x0; x0 = x2; //swap
    y2 = y1; y1 = y0; y0 = y2; //swap
	}

	float dx = x1 - x0;
	float dy = abs(y1 - y0);

	float error = dx / 2.0f;
	int ystep = (y0 < y1) ? 1 : -1;

	int y = int(y0);
	int max_x = int(x1);

	for(int x = int(x0); x < max_x; x += 1) {
	  if (steep) {
		  if(jjLayers[layer].maskedPixel(y, x)) {
		    return true;
		  }
		} else {
		  if(jjLayers[layer].maskedPixel(x, y)) {
		    return true;
		  }
		}

		error -= dy;
		if (error < 0) {
			y += ystep;
			error += dx;
		}
	}

	return false;
}