LUT Previewer

A PyQt5 desktop app for previewing the effect of different LUT files (.cube) to your photos (RAW and non-RAW files supported).
Load an image, add one or more LUTs, and compare results side by side using a draggable split view.
Works in Linux and Windows.

Features

• Split before/after view — drag the divider to compare original vs. LUT-applied
• Multi-LUT sidebar — load a whole folder of LUTs at once and click between them instantly
• Background processing — all LUTs are applied in parallel threads; the UI stays responsive
• Export with LUT applied — saves at the original image resolution, as JPEG, PNG, or TIFF with the currently selected LUT applied.
• Persistent history — previously used LUTs are restored automatically on next launch
• RAW support — reads NEF, CR2, ARW, DNG and other camera RAW formats via rawpy

Requirements

• Python 3.10+
• PyQt5 ≥ 5.15
• numpy ≥ 1.24
• Pillow ≥ 10.0
• rawpy ≥ 0.18 (optional — required for full-resolution RAW files; JPEG/PNG work without it)

Setup

Linux

git clone https://github.com/hestela/lut-previewer
cd lut-previewer
python3 -m venv venv
venv/bin/pip install -r requirements.txt

Windows

First make sure you have Python3 installed and python3.exe can be ran from powershell.

git clone https://github.com/hestela/lut-previewer
cd lut-previewer
python3.exe -m venv venv
.\venv\Scripts\pip.exe install -r .\requirements.txt

Running

Linux

venv/bin/python3 main.py

Windows

.\venv\Scripts\python.exe .\main.py

Usage

1. Click Open Image and select a JPEG, PNG, TIFF, or RAW file
2. Click Add LUT(s)… in the sidebar and select one or more .cube files
3. Click a LUT name in the sidebar to see it applied in the split view
4. Drag the white divider handle to adjust the before/after split
5. Use the View menu to switch between Split / Before / After modes
6. Scroll to zoom, right-click drag to pan, double-click to reset zoom
7. Click Export… to save the current LUT applied at full resolution

LUTs added in previous sessions appear automatically in the sidebar on next launch.

Supported formats

Input images	JPEG, PNG, TIFF, BMP, NEF, CR2, CR3, ARW, DNG, ORF, RW2
LUT files	Adobe .cube (3D LUT, any grid size)
Export	JPEG (quality 100%), PNG, TIFF