Convert images to Apple II lores bytes to write directly to memory.

grconv.py

# Take some image and convert to LoRes bytes
# You should already have it in 16 Apple II colors
# but this will do a nearest color match if not.
from PIL import Image
from math import sqrt

img = Image.open("saved_Preview.BMP")
def distance3d((x1, y1, z1), (x2, y2, z2)):
	return sqrt((x2 - x1)**2 + (y2 - y1)**2 + (z2 - z1)**2)

pixels = img.load() # create the pixel map

colors = [
	(0,0,0), (0xDD,0,0x33), (0,0,0x99), (0xDD,0,0xDD),
	(0,0x77,0), (0x55,0x55,0x55), (0x22,0x22,0xFF), (0x66,0xAA,0xFF),
	(0x88,0x55,0x22), (0xFF,0x66,0), (0xAA,0xAA,0xAA), (0xFF,0x99,0x88),
	(0,0xDD,0), (0xFF,0xFF,0), (0,0xFF,0x99), (0xFF,0xFF,0xFF)
]

bytes = []
for j in range(img.size[1]/2):    # For every other row because we stack them into one GR byte
	for i in range(img.size[0]/2):    # for every other col because i'm taking an input image with doubled horizontal pixels
		p1 = img.getpixel((i*2,j*2))
		p2 = img.getpixel((i*2,(j*2)+1))

		nearest_idx1 = colors.index(min(colors, key=lambda x: distance3d(x, p1)))
		nearest_idx2 = colors.index(min(colors, key=lambda x: distance3d(x, p2)))
		byte = nearest_idx1 + (nearest_idx2*16)
		bytes.append(byte)
		#img.show()

newFile = open("out.GR", "wb")
newFileByteArray = bytearray(bytes)
newFile.write(newFileByteArray)