My apologies. I spent too much time in the pub on Sunday. And I went to a funeral on Monday.
I have attached an example sketch that renders some standard BMP files on a ST7735 screen.
The BMPs were generated by IrfanView from a regular 24-bit JPEG / BMP / PNG image.
And then the colour resolution reduced to 256 colours (8-bit palette) and 4-bit (16 colour palette)
The 16-colour does not look too bad. 256-colour looks good. IrfanView or GIMP might be able to do a better job if you configure carefully.
I have only tested on a Seeeduino and a Due. You might run into PROGMEM issues with your mega1284.
I have not looked at your code yet. I strongly advise against using decimal numbers in your data arrays. Hex is a lot easier to read.
David.
show_ladies_P.zip (98.9 KB)