lv_imgbtn_set_src() function
Set images for a state of the image button
Arguments
state
for which state set the new image
src_left
pointer to an image source for the left side of the button (a C array or path to a file)
src_mid
pointer to an image source for the middle of the button (ideally 1px wide) (a C array or path to a file)
src_right
pointer to an image source for the right side of the button (a C array or path to a file)