How to modify the position of the background image of the object

Hi, first, I created an object, and then set a background image for the object. But the size of the background image is smaller than the size of the object. The background image is centered by default, and I want the background image to be displayed on the left. Which one should I use API?

a simple code is as follows:

lv_obj_t *obj1 = lv_obj_create(lv_scr_act());
lv_obj_set_size(obj1, 320, 240);

// image size: 252*240
lv_obj_set_style_bg_img_src(obj1, "A:/assets/images/work_bg.png", LV_PART_MAIN);