Nexus 5 imagedata extraction

imagedata-extract.py

import struct
import imageio
import numpy as np
import sys

if len(sys.argv) < 2:
    print ("Usage: image-extract.py [imgdata.image]")
    exit(0)

f = open(sys.argv[1], "rb")
header = f.read(0x18)

magic, unk, res_table_cnt, unk2, unk3 = struct.unpack("<8sLLLL", header)
magic = magic.rstrip(bytes([0x00])).decode('utf-8')
print(magic, unk, res_table_cnt, unk2, unk3)

res_table_offs = 0x18
f.seek(res_table_offs)

for i in range(0, res_table_cnt):
    f.seek(res_table_offs + i * 0x28)
    res_ent = f.read(0x28)
    name, width, height, offs_x, offs_y, offset, size = struct.unpack("<16sLLLLLL", res_ent)
    name = name.rstrip(bytes([0x00])).decode('utf-8')
    print(name, hex(offset), hex(size), width, height, offs_x, offs_y)

    f.seek(offset)    
    image_rle = f.read(size)
    image_array = np.zeros((height,width,3), dtype=np.uint8)
    xpos = 0
    ypos = 0

    for j in range(0, size>>2):
        num, r, g, b = image_rle[j*4:(j+1)*4]#struct.unpack("<BBBB", f.read(4))
        for k in range(0, num):
            image_array[ypos][xpos] = (r,g,b)
            xpos += 1
            if (xpos >= width):
                xpos = 0
                ypos += 1
    imageio.imwrite(name + '.png', image_array)

f.close()