dngpy 0.1.2

Python bindings for Adobe DNG SDK

PyDNG — Python bindings for the Adobe DNG SDK

中文版

This project provides fundamental Python bindings for the Adobe DNG SDK so you can read and write DNG (Digital Negative) files from Python.

Features

• Read DNG files
• Write DNG files
• Extract metadata (EXIF, camera info, and more)
• Access image data (Stage1 and Stage3)
• Set image data from NumPy arrays
• Read and write baseline exposure
• Works naturally with NumPy

Repository layout

• src/pydng/ — installable Python package (__init__.py, type stubs, py.typed).
• bindings/ — C++ layer for the pybind11 extension (_native) and dng_validate:
  • include/ — headers (dng.h, utils.h, pch.h)
  • src/ — pydng_bindings.cpp, dng.cpp
  • main.cpp — entry point for the dng_validate utility.
• extern/ — vendored SDKs and third-party code (DNG SDK, XMP, libjxl, pybind11, etc.).

CI packaging

On pushes and pull requests, GitHub Actions uses a two-stage pipeline:

1. Stage 1: Build the core dng shared library for Linux and Windows.
2. Stage 2: Use cibuildwheel to build Python wheels for all compatible versions (Python 3.8 to 3.12) using the pre-built core library.

This ensures efficient build times and broad compatibility.

Quick start

Install with pip (recommended)

The simplest approach is a one-step install:

# Install from the project root
pip install .

# Editable install (development)
pip install -e .

# Install from a Git repository
pip install git+https://github.com/yourusername/PyDNG.git

pip pulls in build dependencies and drives the CMake build for you.

Manual build

Use a manual CMake workflow if you need full control over configuration and compilation.

Requirements

• CMake 3.15 or newer
• Python 3.8 or newer (including development headers for the interpreter you build against)
• A C++14-capable compiler (GCC 4.9 or newer on Linux, Clang 3.4 or newer on macOS, MSVC 2015 or newer on Windows)
• pybind11 (via the extern/pybind11 git submodule, or fetched automatically if missing)

Standard build (Recommended)

To build everything (the core library and the Python extension) at once for your current Python environment:

pip install .

Advanced: Separated build

If you want to build the core library once and then build the bindings later (similar to the CI process):

1. Build the core library

mkdir build
cd build
cmake .. -DBUILD_PYTHON_BINDINGS=OFF -DBUILD_DNG_VALIDATE=ON -DCMAKE_INSTALL_PREFIX=../install_dir
cmake --build . --target install --config Release

2. Build the Python bindings using the pre-built core

cd ..
# Point to the install_dir from the previous step
pip install . --config-settings=cmake.args="-DBUILD_DNG_LIBRARY=OFF -DPREBUILT_DNG_PATH=./install_dir"

Building dng_validate for C++ verification

To build the dng_validate command-line tool for verifying your C++ changes:

mkdir build
cd build
cmake .. -DBUILD_DNG_VALIDATE=ON -DBUILD_PYTHON_BINDINGS=OFF
cmake --build . --config Release --target dng_validate

The executable will be located in the build directory (or build/Release on Windows).

Usage

Basic example — read a DNG

import pydng
import numpy as np

# Load from path (raises RuntimeError on failure)
dng = pydng.Dng("input.dng", ignore_enhanced=False)

meta = dng.get_meta()
print(f"Camera: {meta.make} {meta.model}")
print(f"Image size: {meta.width} x {meta.height}")
print(f"ISO: {meta.iso}")
print(f"Exposure time: {meta.exposure_time} s")

data = dng.get_data(enhanced=False)
numpy_array = data.to_numpy()
print(f"Image shape: {numpy_array.shape}")

You can still use dng = pydng.Dng() followed by dng.read(path) if you prefer checking ErrorCode instead of exceptions.

Write a DNG

import pydng
import numpy as np

height, width, channels = 1000, 1500, 3
image_data = np.random.randint(0, 65535, size=(height, width, channels), dtype=np.uint16)

dng = pydng.Dng()

# 3 = ttShort (16-bit unsigned)
dng.set_data(image_data, 3, enhanced=False)

meta = pydng.DngMeta()
meta.make = "My Camera"
meta.model = "Example"
meta.width = width
meta.height = height
meta.iso = 100
meta.exposure_time = 1.0 / 60.0
meta.f_number = 2.8
meta.focal_length = 50.0

dng.set_meta(meta)

error_code = dng.write("output.dng")

API reference

Class Dng

Main entry point for reading and writing DNG files.

Constructor

• Dng() — empty object; use read() to load a file.
• Dng(path: str, ignore_enhanced: bool = False) — load path immediately; raises RuntimeError on failure (same behavior as read() returning a non-NONE code).

Methods

• get_bayer_pattern() -> str
  For a 2×2 rectangular RGB CFA, returns "RGGB", "GRBG", "BGGR", or "GBRG" (row-major tile); otherwise "".

• set_bayer_pattern(pattern: str) -> None
  Sets the 2×2 Bayer phase; pattern must be one of those four strings (case-insensitive). Requires a 3-plane RGB CFA (or uninitialized mosaic, which is initialized with SetRGB()).

• read(path: str, ignore_enhanced: bool = False) -> ErrorCode
  Load a DNG from disk (return code; no exception on error).

• write(path: str) -> ErrorCode
  Save a DNG to disk.

• get_data(enhanced: bool = False) -> DngData
  Return image data. enhanced=True selects Stage3; False selects Stage1.

• set_data(data: np.ndarray, pixel_type: int, enhanced: bool = False) -> None
  Set image data. data has shape (height, width, channels).
  pixel_type: numeric code (1 = ttByte, 3 = ttShort, 8 = ttSShort, 4 = ttLong).

• get_meta() -> DngMeta
  Return metadata.

• set_meta(meta: DngMeta) -> None
  Apply metadata.

• get_baseline_exposure() -> float
  Baseline exposure value.

• set_baseline_exposure(exposure: float) -> None
  Set baseline exposure.

• get_white_balance() -> List[float]
  Get white balance neutral vector (e.g., [r, g, b] gains).

• set_white_balance(wb: List[float]) -> None
  Set white balance neutral vector.

Class DngMeta

Metadata for a DNG file.

Fields

• make, model: camera make and model
• software: software string
• artist, copyright: attribution and rights
• width, height: image dimensions
• raw_width, raw_height: raw dimensions
• exposure_time: exposure in seconds
• f_number: aperture
• focal_length: focal length in mm
• iso: sensitivity
• focal_length_35mm: 35 mm equivalent focal length
• date_time, date_time_original: timestamps
• is_monochrome: monochrome flag
• color_planes, color_space: color layout and space

Class DngData

Image buffer returned by get_data().

Fields

• width, height, channels: layout
• pixel_type: internal type code
• top, left: active-area offset

Methods

• to_numpy() -> np.ndarray
  Export as a NumPy array.

Constants — ErrorCode

• NONE: success
• READ_FILE: read failure
• WRITE_FILE: write failure
• BAD_FORMAT: invalid format
• UNKNOWN: other error

Pixel type codes (see also PIXEL_TYPES.md):

• 1 — ttByte (8-bit unsigned)
• 3 — ttShort (16-bit unsigned)
• 8 — ttSShort (16-bit signed)
• 4 — ttLong (32-bit unsigned)

Examples

See the examples/ directory:

• example_read_dng.py — load a DNG and print information
• example_write_dng.py — build and write a DNG

Notes

1. Memory — DngData lifetime is tied to the conversion to NumPy; do not try to manually free the underlying pointer.

2. Pixel types — Choose pixel_type in set_data() so it matches the dtype and layout of your array.

3. Layout — Image arrays are expected as (height, width, channels).

4. Windows paths — Paths are handled with the appropriate wide-character APIs where required.

Troubleshooting

Import errors

1. Confirm the extension module built successfully.
2. Ensure the build output is on PYTHONPATH or installed into site-packages.
3. On Windows, native dependencies (dng.dll and related) must be discoverable (same folder as the .pyd or on PATH).

Build failures

1. Install the Python development package for your interpreter (headers and libs).
2. Verify CMake finds the intended Python (Python3_ROOT, CMAKE_PREFIX_PATH, etc.).
3. Confirm you have a working C++14 toolchain.

License

This project builds on the Adobe DNG SDK; use and redistribution must comply with the Adobe license terms that apply to the SDK and to this repository.