psdparse

Pure C++17 PSD (Photoshop) reader/writer library, with pybind11-based Python bindings.

• Lazy I/O: PSD pixel data is not copied into memory at parse time. Only the structural metadata (a few hundred KB even for large files) is read upfront; layer pixels are paged in on demand via mmap or stream callbacks.
• Round-trip save: load(p) -> save(q) produces a byte-identical PSD file.
• Python wrapper: import psdparse → PSDFile.load(path) / layer_image(i) / merged_image() / save(path).

The library was extracted from the psdfile kirikiri plugin in 2026. psdfile now consumes this library as a submodule.

Architecture (quick read)

See docs/ARCHITECTURE.md for full details.

IteratorBase (psdbase.h, pure virtual — parser only sees this)
├── MemoryReader   (psdparse.h)  ... mmap / contiguous buffer
└── StreamReader   (psdparse.h)  ... arbitrary seekable stream
    └── Source (pure virtual; subclass per backend)
        ├── IStreamSource              ... std::istream
        └── (your custom Source)       ... e.g. iTJSBinaryStream wrapper

WriterBase (psdwrite.h, pure virtual — symmetric to IteratorBase)
└── FileWriter (FILE*)

psd::PSDFile::load(const char *path) mmaps a local file. loadFromStream(std::istream&) / loadFromReader(IteratorBase&) accept arbitrary I/O. save(const char *path) writes the loaded data back as PSD.

All public path arguments are UTF-8 (char *). On Win32, conversion to UTF-16 happens internally via psd::utf8ToWide (inline in psdbase.h).

Build

Requires CMake 3.16+, MSVC (Windows), and vcpkg with VCPKG_ROOT set.

$env:VCPKG_ROOT = 'd:\vcpkg'

# C++ library + CLI (static CRT)
cmake --preset x64-windows
cmake --build --preset x64-windows --config Release

# C++ library + Python module (dynamic CRT, matches CPython)
cmake --preset x64-windows-python
cmake --build --preset x64-windows-python --config Release

Makefile is a thin wrapper:

make PRESET=x64-windows prebuild build
make PRESET=x64-windows-python prebuild build

Build artifacts:

• build/x64-windows/psdparse/Release/psdparse_cli.exe
• build/x64-windows-python/python/Release/psdparse.cp312-win_amd64.pyd

Dependencies: vcpkg installs zlib only.

Python API

import psdparse

p = psdparse.PSDFile()
p.load(r"path/to/file.psd")   # mmap-backed

print(p.header.width, p.header.height, len(p.layers))
for layer in p.layers:
    print(layer.name_unicode, layer.blend_mode.name, layer.opacity)

bgra = p.merged_image()                # bytes, BGRA, 4*W*H
layer_bgra = p.layer_image(0, "masked") # bytes, BGRA, 4*w*h

p.save(r"out.psd")              # byte-identical round-trip

Full API reference: docs/PYTHON_API.md.

Tests

Tests live under tests/ and use pytest. They need two sample PSDs at the repo root (not in git — see below).

# After building with x64-windows-python preset:
python -m pytest -v

Sample PSDs

The 27 pytest tests use these files:

File	Size	Description
UI-PSDサンプル.psd	800×600, 50 layers, ~2 MB	UI button mock-up. Folder groups, transparent overlays.
園部由夏_a.psd	2500×3500, 28 layers, ~21 MB	Illustration. PASS_THROUGH groups, Unicode layer names (luni records).

Place them at the repo root (the conftest.py also checks tests/data/ first). They are listed in .gitignore. If you can't source them, the tests will skip rather than fail.

tools/psd_export.py

python tools/psd_export.py input.psd [--out-dir DIR] [--mode masked|image|mask]

Outputs layers.json (full layer metadata), merged.png (composite), and per-layer PNGs.

License

MIT — see LICENSE.