#!/usr/bin/env python3
from PIL import Image
import sys
import struct
import zlib
from os.path import basename


def process_rgb(w, h, pix):
    data = bytes()
    for j in range(h):
        for i in range(w):
            r, g, b = pix[i, j]
            c = ((r & 0xF8) << 8) | ((g & 0xFC) << 3) | ((b & 0xF8) >> 3)
            data += struct.pack('>H', c)
    return data


def process_grayscale(w, h, pix):
    data = bytes()
    for j in range(h):
        for i in range(w // 2):
            l1, l2 = pix[i * 2, j], pix[i * 2 + 1, j]
            c = (l1 & 0xF0) | (l2 >> 4)
            data += struct.pack('>B', c)
    return data


def process_image(ifn, savefiles=False):
    im = Image.open(ifn)
    w, h = im.size
    print('Opened %s ... %d x %d @ %s' % (ifn, w, h, im.mode))

    if im.mode == 'RGB':
        print('Detected RGB mode')
    elif im.mode == 'L':
        if w % 2 > 0:
            print('PNG file must have width divisible by 2')
            return 3
        print('Detected GRAYSCALE mode')
    else:
        print('Unknown mode:', im.mode)
        return 4

    pix = im.load()

    bname = basename(ifn[:-4])
    ofn_h = '%s.h' % bname
    ofn_py = '%s.py' % bname

    if im.mode == 'RGB':
        ofn = '%s.toif' % bname
        pixeldata = process_rgb(w, h, pix)
    else:
        ofn = '%s.toig' % bname
        pixeldata = process_grayscale(w, h, pix)
    z = zlib.compressobj(level=9, wbits=10)
    zdata = z.compress(pixeldata) + z.flush()
    zdata = zdata[2:-4]  # strip header and checksum

    data = b''
    if im.mode == 'RGB':
        data += b'TOIf'
    else:
        data += b'TOIg'
    data += struct.pack('<HH', w, h)
    data += struct.pack('<I', len(zdata))
    data += zdata

    if savefiles:
        with open(ofn, 'wb') as f:
            f.write(data)
            print('Written %s ... %d bytes' % (ofn, len(data)))
        with open(ofn_py, 'wb') as f:
            f.write(('%s = %s\n' % (bname, data)).encode())
            print('Written %s ... %d bytes' % (ofn_py, len(data)))
        with open(ofn_h, 'wt') as f:
            f.write('static const uint8_t toi_%s[] = {\n' % bname)
            f.write('    // magic\n')
            if im.mode == 'RGB':
                f.write("    'T', 'O', 'I', 'f',\n")
            else:
                f.write("    'T', 'O', 'I', 'g',\n")
            f.write('    // width (16-bit), height (16-bit)\n')
            f.write('    0x%02x, 0x%02x, 0x%02x, 0x%02x,\n' % (w & 0xFF, w >> 8, h & 0xFF, h >> 8))
            l = len(zdata)
            f.write('    // compressed data length (32-bit)\n')
            f.write('    0x%02x, 0x%02x, 0x%02x, 0x%02x,\n' % (l & 0xFF, (l >> 8) & 0xFF, (l >> 16) & 0xFF, l >> 24))
            f.write('    // compressed data\n')
            f.write('   ')
            for b in zdata:
                f.write(' 0x%02x,' % b)
            f.write('\n};\n')
            print('Written %s ... done' % ofn_py)

    return data


def main():
    if len(sys.argv) < 2:
        print('Usage png2toi image.png')
        return 1

    ifn = sys.argv[1]
    if not ifn.endswith('.png'):
        print('Must provide PNG file')
        return 2

    process_image(ifn, savefiles=True)


main()
