Код, который у вас есть, работает следующим образом:
// draw the my_pic sprite to bitty
draw_sprite(bitty,my_pic,my_pic_x,my_pic_y);
// status now: bitty contains my_pic
// draw bitty to the screen
blit(bitty, screen, 0,0,0,0,640,480);
// status now: screen contains my_pic by way of bitty
// clear bitty
clear_bitmap(bitty);
// status now: screen contains my_pic by way of a former
// version of bitty, bitty is now empty
// draw my_pics to buffer
draw_sprite(buffer,my_pics,my_pics_x,my_pics_y);
// status now: screen contains my_pic, bitty is empty,
// buffer contains my_pics
// draw buffer to the screen
blit(buffer, screen, 0,0,0,0,640,480);
// status now: screen and buffer both contain my_pics,
// bitty is empty
// clear the buffer
clear_bitmap(buffer);
// status now:
//
// screen contains my_pics
// bitty and buffer are empty
Я думаю, вы захотите что-то более похожее на:
// clear buffer
clear_bitmap(buffer);
// status now: buffer is empty
// draw my_pic to buffer
draw_sprite(buffer,my_pic,my_pic_x,my_pic_y);
// status now: buffer contains my_pic
// draw my_pics to buffer
draw_sprite(buffer,my_pics,my_pics_x,my_pics_y);
// status now: buffer contains my_pic, with my_pics on top
// copy buffer to the screen
blit(buffer, screen, 0,0,0,0,640,480);
// status now: buffer and screen contain my_pic, with my_pics on top