bt_from_raw.py

import sys
import bluetooth
from PIL import Image, ImageOps
import numpy as np
import os

def convert_image_to_bitpacked(filepath, width=384, height=390):
    # Load the image with RGBA mode to preserve alpha
    img = Image.open(filepath).convert("RGBA")

    # Flatten onto white background
    background = Image.new("RGBA", img.size, (255, 255, 255, 255))
    img = Image.alpha_composite(background, img).convert("L")

    # Resize to expected printer dimensions
    img = img.resize((width, height), Image.Resampling.LANCZOS)

    # Convert to 1-bit using standard thresholding without inversion
    img_bw = img.point(lambda x: 255 if x < 128 else 0, mode="1")

    # Convert to numpy and bitpack
    bits = np.array(img_bw, dtype=np.uint8)
    packed = np.packbits(bits, axis=1)
    return packed.tobytes()

def main(image_path, mac):
    # Load original captured binary
    if not os.path.exists("print.bin"):
        print("Missing 'raw_capture.bin'. Please place it next to this script.")
        sys.exit(1)

    with open("print.bin", "rb") as f:
        raw = f.read()

    # Locate GS v 0 m raster command
    index = raw.find(b"\x1D\x76\x30\x00")
    if index == -1:
        print("Raster command not found in raw stream.")
        sys.exit(1)

    xL, xH = raw[index+4], raw[index+5]
    yL, yH = raw[index+6], raw[index+7]
    width_bytes = xL + (xH << 8)
    height = yL + (yH << 8)
    image_size = width_bytes * height

    start = index + 8
    end = start + image_size

    print(f"Image region: offset={start}, size={image_size} bytes")

    # Convert and bitpack image
    print("Converting image...")
    image_data = convert_image_to_bitpacked(image_path, width_bytes * 8, height)

    if len(image_data) != image_size:
        print(f"Image size mismatch: expected {image_size}, got {len(image_data)}.")
        sys.exit(1)

    # Splice into raw stream
    patched = raw[:start] + image_data + raw[end:]

    # Send via Bluetooth
    print(f"Connecting to {mac}...")
    sock = bluetooth.BluetoothSocket(bluetooth.RFCOMM)
    sock.connect((mac, 1))
    print("Sending...")
    sock.send(patched)
    sock.close()
    print("Done.")

if __name__ == "__main__":
    if len(sys.argv) != 3:
        print("Usage: replace_and_send_from_hex_fixed.py <image.png> <MAC_ADDRESS>")
        sys.exit(1)
    main(sys.argv[1], sys.argv[2])