Tektronix 11801 Screen Capture

decode-11801-screenshot.py

#!/usr/bin/env python3

import sys
import re
import datetime
from PIL import Image
import serial
import subprocess

device = '/dev/ttyUSB0'
speed = 19200


colors = [
    bytes.fromhex('000000'),
    bytes.fromhex('ffffff'),
    bytes.fromhex('00ff00'),
    bytes.fromhex('00ffff'),
    bytes.fromhex('ff00ff'),
    bytes.fromhex('0000ff'),
    bytes.fromhex('555555'),
    bytes.fromhex('ff0000')
]

def parse11801Stream(stream):
    data = bytearray()
    title = stream.readline()
    m = re.search(b'date: (..-...-..) time: (..:..:..)', title)
    if not m:
        return
    timestamp = datetime.datetime.strptime(m.group(1).decode().strip() + 'T' +
                                           m.group(2).decode().strip(),
                                           '%d-%b-%yT%H:%M:%S')
    filename = timestamp.isoformat() + '.png'
    print('decoding : ' +  filename)
    cols = int(stream.readline().decode('utf-8'))
    rows = int(stream.readline().decode('utf-8'))
    byte = stream.read(1)
    byte = stream.read(1)
    while byte:
        val = int.from_bytes(byte, 'little')
        if (val & 0xc0) == 0x40:
            count = 1
        if (val & 0xc0) == 0x80:
            count = 2
        if (val & 0xc0) == 0xc0:
            count = 3
        if (val & 0xc0) == 0x00:
            byte = stream.read(1)
            val2 = int.from_bytes(byte, 'little')
            if val2 >= 4:
                count = val2
            else:
                byte = stream.read(1)
                val3 = int.from_bytes(byte, 'little')
                count = (val2<<8) | val3
        for i in range(count):
            data += colors[val & 0x7]
            data += colors[(val & 0x38)>>3]
        if 3*rows*cols == len(data):
            break
        byte = stream.read(1)
    if 3*rows*cols != len(data):
        print(title,
                  'length mismatch({:d} != {:d})'.format(3*rows*cols,
                                                         len(data)))
    try:
        image = Image.frombytes('RGB', (cols, rows), bytes(data))
        image = image.transpose(Image.ROTATE_90)
        print('writing ' + filename)
        image.save(filename)
        print('transferring ' + filename)
        subprocess.Popen(['scp', './' + filename,
                          'tyapo@192.168.1.14:Documents/11801_images/']).wait()
    except:
        pass


port = serial.Serial(device, speed)
while True:
        parse11801Stream(port)