gif2nes.py

from PIL import Image, ImageSequence
import array as arr 

#assume gif is 4 colors ( and the 1st 4 )  
#assume gif is 128x128 

def frame2nes(input,basename,index):
	(w, h) = input.size
	# parse image by 8x8's 
	outname = basename + "_" + str(index) + ".chr"
	chrFile = open(outname, "wb")
	# for height in steps of 8 

	for y in range(0, h, 8):
		# for width in steps of 8 
			for x in range(0, w, 8):
				# clear the bitset
				bitset0=[]
				bitset1=[]
				# for each pixel Y
				for iy in range(0,8):
					# reset the byte
					bitsa = 0
					bitsb = 0
					# for each pixel X
					for ix in range(0,8):
						# flip the index 
						fx = 7-ix
						# get the color ( we assume 4 color gif )
						pixel = input.getpixel((x+ix,y+iy))
						# set the bits 
						if pixel&1==1:
							bitsa|=1<<fx
						if pixel&2==2:
							bitsb|=1<<fx
					# store the bytes per Y 
					bitset0.append(bitsa)
					bitset1.append(bitsb)
				# save the set out as bytes
				# nes stores bitplanes 8 bytes per plane * 2
				for iy in range(0,8):
					chrFile.write(bitset0[iy].to_bytes(1,byteorder='big'))
				for iy in range(0,8):
					chrFile.write(bitset1[iy].to_bytes(1,byteorder='big'))

	chrFile.close()

def gif2nes(name):
	newname = name + ".gif"
	im = Image.open(newname)
	index = 0
	for frame in ImageSequence.Iterator(im):
		frame2nes(frame,name,index)
		index += 1

gif2nes("runnes")