// In lcd_gfx.h einfügen:

void lcd_drawBitmap(uint8_t px, uint8_t py, const uint8_t bitmap[]);  // draw bitmap at pixel position x, y.


// In lcd_gfx.c einfügen:

void lcd_drawBitmap(uint8_t px, uint8_t py, const uint8_t bitmap[]) {
	uint8_t size_x = pgm_read_byte(&bitmap[0]);  // width of bitmap in px
	uint8_t size_y = pgm_read_byte(&bitmap[1]);  // height of bitmap in px
	uint8_t rows;
	uint8_t x, y;
	uint16_t bufadr;
	uint8_t mask;
	uint8_t bm;
	
	// calculate count of rows (1 row = 8 px = 1 byte)
	rows = size_y / 8;
	if (size_y % 8 != 0)
		rows++;

	// display all bytes in bitmap. bitmap starts at index 2
	for (uint16_t i = 2; i < rows * size_x + 2; i++) {
		bm = pgm_read_byte(&bitmap[i]);

		y = (i - 2) / size_x * 8 + py;
		x = (i - 2) % size_x + px;
		bufadr = y / 8 * DISPLAY_WIDTH + x;
		
		// build bitmap mask 
		mask = 0;
		for (uint8_t n = 0; n < y % 8; n++)
			mask += 1 << n;
			
		// display upper byte
		displayBuffer[bufadr] &= mask;
		displayBuffer[bufadr] |= (bm << (y % 8));

		// display lower byte, if necessary	
		if (y % 8 != 0)	{
			mask = ~mask;
			bufadr += DISPLAY_WIDTH;
			displayBuffer[bufadr] &= mask;
			displayBuffer[bufadr] |= (bm >> (8 - y % 8));
		}
	}
}