xmp2cube

Convert Adobe Camera Raw / Lightroom Look presets (.xmp) into standard .cube 3D LUT files, for use in DxO PhotoLab, DaVinci Resolve, OBS, or any LUT-capable application.

Many ACR/Lightroom "Look" presets carry their color grade as an embedded 3D RGB lookup table. xmp2cube extracts that table and writes it out as a portable .cube LUT — no Adobe software required, no dependencies beyond the Python standard library.

How it works

A Look preset embeds its color table in a crs:Table_<hash> attribute. That value is Adobe's dng_big_table serialization: a zlib-compressed binary blob, text-encoded with a Z85-like base85 variant. xmp2cube:

1. Decodes the base85 text and inflates the zlib stream.
2. Parses the binary dng_rgb_table structure (a 3D RGB LUT, stored as uint16 deltas from a neutral identity ramp).
3. Reads the table's own color space — its primaries and transfer function are recorded in the table and used directly; nothing is assumed.
4. Writes a .cube file, either verbatim or color-managed into sRGB.

Requirements

• Python 3 (standard library only — no pip install needed).

Usage

# Convert every .xmp in the current directory (native mode, output to ./cube)
python xmp2cube.py

# Choose an output directory and mode
python xmp2cube.py -m srgb -o cube_srgb/

# Convert specific files, with details printed
python xmp2cube.py "My Look.xmp" "Another Look.xmp" -v

# sRGB mode at a custom grid resolution (default 33)
python xmp2cube.py -m srgb -s 65

Option	Meaning
inputs	One or more .xmp files or directories (default: current directory).
-o, --outdir	Output directory (default: ./cube).
-m, --mode	native or srgb (default: native).
-s, --size	Grid size for srgb (resampled) mode (default: 33).
-v, --verbose	Print each table's dimensions and color space.

Output modes

Mode	Color space of the .cube	When to use
native	The table's own primaries + transfer function, written verbatim.	Lossless. Best when your application can be told the LUT's exact color space.
srgb	sRGB primaries + sRGB gamma, in and out.	Universal. The look is resampled from the table's declared space into a plain sRGB-in/sRGB-out LUT. Colors outside the sRGB gamut are clipped.

native is lossless but only useful if your host lets you declare the LUT's input/output color space to match the table (e.g. Rec.2020). srgb is the safe, unambiguous choice for most workflows — feed it sRGB, get sRGB back.

Matching the color space in your host

A .cube file carries raw numbers; it does not tell the application what primaries or transfer function those numbers live in. You must set that to match the .cube you exported, or tones will shift (for example, a gamma-1.8 table interpreted as Rec.2020 will look too light). Each generated .cube includes header comments naming its declared color space.

• srgb mode → set the LUT color space to sRGB. (Unambiguous, recommended.)
• native mode → set it to match the table's declared space (shown in -v output and in the .cube header). Some spaces — e.g. ProPhoto with a 1.8 gamma — have no exact equivalent in a given host; use srgb mode for those.

Scope and limitations

xmp2cube extracts the preset's embedded 3D RGB LUT — and only that. It is deliberately narrow:

• Only the embedded color table is converted. Other preset adjustments (exposure, tone curve, HSL, masks, profile selection, etc.) are not baked in. If a preset's look depends heavily on settings outside the embedded table, the .cube will not fully reproduce it. Presets often also rely on a specific camera/input profile being applied first; the .cube represents the grade on top of whatever input you feed it.
• 3D RGB tables only. The parser handles the standard dng_rgb_table (3 dimensions). 1D curves and HSV/hue-based Look tables are not supported.
• The look is exported at full strength (table amount = 1.0). The preset's min/max amount range is read but not applied.
• Table discovery looks for a crs:Table_<hash> attribute and uses the first one found. Presets that store the table differently, or carry several tables, may not convert as expected.
• Color spaces are limited to those Adobe defines: primaries sRGB, Adobe RGB, ProPhoto, Display P3, Rec.2020 and transfer functions Linear, sRGB, 1.8, 2.2, Rec.2020.

Project layout

xmp2cube.py    # the converter (single file, stdlib only)
README.md

License

See repository for license details.