1 1-bit bilevel, stored with the leftmost pixel in the most significant bit.
0 means black, 1 means white.
1;I 1-bit bilevel, stored with the leftmost pixel in the most significant
bit. 0 means white, 1 means black.
1;R 1-bit reversed bilevel, stored with the leftmost pixel in the lease
significant bit. 0 means black, 1 means white.
L 8-bit greyscale. 0 means black, 255 means white.
L;I 8-bit inverted greyscale. 0 means white, 255 means black
P 8-bit palette-mapped image
RGB 24-bit true colour, stored as (red, green, blue)
BGR 24-bit true colour, stored as (blue, green, red)
RGBX 24-bit true colour, stored as (blue, green, red, pad)
RGB;L 24-bit true colour, line interleaved (first all red pixels, the all
green pixels, finally all the blue pixels)