lvglimg

Decode LVGL .bin image files to PNG — including v8 + v9 headers and NONE / RLE / LZ4 / LZ4_HC compression.

LVGL's own LVGLImage.py is a one-way encoder: it can write compressed bins, but from_bin ignores the flags field and cannot decompress them back. lvglimg fills that gap, producing pixel-accurate PNGs from real device asset bins.

• Self-contained — depends only on Pillow + lz4. No LVGL source tree, no LVGLImage.py on disk.
• All v9 color formats — L8, indexed (I1/2/4/8), alpha-only (A1/2/4/8), RGB565, RGB888, ARGB8888, XRGB8888, ARGB8565, RGB565A8.
• v8 true-color — TRUE_COLOR / TRUE_COLOR_ALPHA (BGRA).
• CLI + library — use it on the command line or import the decoder.

Install

pip install lvglimg

CLI

# single file → sibling .png
lvglimg image.bin

# explicit output path
lvglimg image.bin out.png

# batch a directory (recursive) → out/<same subdirs>/*.png
lvglimg assets/ out/
# default: a sibling '<input>_preview/' dir next to the input
lvglimg assets/       # → assets_preview/ (sibling of assets/)
# finds assets/*.bin AND assets/**/<sub>/*.bin; mirrors the subdir layout
# in the output dir (avoids name collisions across folders)

$ lvglimg --version
lvglimg 0.0.1

Library

from lvglimg.decoder import decode, decode_file

# from bytes
img = decode(bin_bytes)
img.save("out.png")

# from a file path
img = decode_file("image.bin")

decode() returns a PIL.Image.Image (mode RGBA, RGB, or L depending on the source format), so you can inspect, transform, or re-encode it however you like.

How it works

The LVGL v9 on-disk layout is a 12-byte header followed by a body that may be a compress block:

header: magic(0x19) cf flags w h stride reserved
body  : [method u32][clen u32][raw_len u32][payload]   # iff flags & 0x08

lvglimg reads the flags field to detect compression (the same bit LVGL sets when encoding), decompresses RLE / LZ4 / LZ4_HC, then unpacks pixels to RGBA using the same channel layout and bit_extend upscaling LVGL renders on-device — so output matches the display. v8 files (no magic byte) are dispatched to the 4-byte bitfield header path.

Note — v8 support covers the true-color BGRA layouts (cf=4/5) used by miwear assets. Other legacy v8 formats raise a clear error rather than silently producing garbage.

Development

pip install -e ".[dev]"
pytest            # 14 tests, runs against src/ with no install
ruff check src tests main.py
mypy
./main.py image.bin   # run from source, no install

License

This project is licensed under the Apache License, Version 2.0. See LICENSE or https://www.apache.org/licenses/LICENSE-2.0 for the full text.