如何创建宽度和高度与连接的窗口不同的XCB图像？

#include <xcb/xcb.h>

xcb_connection_t *connection = xcb_connect(NULL, NULL);

const xcb_setup_t *setup = xcb_get_setup(connection);
xcb_screen_t *screen = xcb_setup_roots_iterator(setup).data;

xcb_window_t window = xcb_generate_id(connection);
xcb_create_window(connection, XCB_COPY_FROM_PARENT, window, screen->root, x, y, width, height, border_width, XCB_WINDOW_CLASS_INPUT_OUTPUT, screen->root_visual, value_mask, value_list);

xcb_pixmap_t pixmap = xcb_generate_id(connection);
xcb_create_pixmap(connection, screen->root_depth, pixmap, window, width, height);

xcb_disconnect(connection);