File specification for LV_IMG_CF_ALPHA_1/2/4/8 and LV_IMG_CF_INDEXED_1/2/4/8/16/32

Description

Is there a file specification used for LV_IMG_CF_ALPHA_1/2/4/8 and LV_IMG_CF_INDEXED_1/2/4/8/16/32 so that convert a 32 bit rgb byte array to either of these formats?

What MCU/Processor/Board and compiler are you using?

nRF52832, PineTime, Zephyr

What LVGL version are you using?

8.3

What do you want to achieve?

Converting bytes from a 32 bit RGB format to a format needing less memory.