Hello,
Thanks for providing an example of the icons.
As these are quite basic two colour images you have a couple options to achieve the inverted image.
The first and simplest option would be to use a bitmap format that uses less bits per pixel for these icon, this should allow you to fit both the normal and inverted icons into RAM_G. For example if you were to use L4 bitmaps these would take up 1/4 of the space in RAM_G that a RG565 bitmap would occupy.
The following should be useful for you:
AN_314 FT800 Advanced Technologies - Working with BitmapsYou could also look into using bitmap cells with L1/L4 bitmaps so that both the inverted and non inverted icon are loaded into RAM_G as one bitmap, please see the above Application Note.
The final option would be to use a bitmap format which supports the Alpha channel (such as ARGB2). This way you would create the icon with a transparent background, after which you can colour the arrow and background when placing the bitmap on your display.
Best Regards,
FTDI Community