openICE

An open reimplementation of Applied Science Fiction's Digital ICE infrared dust-and-scratch removal in C#. It reads an RGBI DNG and writes a clean RGB DNG. Based on the Nikon Coolscan LS-5000/9000 profile in Nikon Scan 4.

The original tool is tuned for Coolscan scanners; using other scanners may not show the best results. To use this tool for non-Coolscan scanners, see Using non-Coolscan Scanners.

How to Use - GUI

If you want a quick, simple tool for ICE, download openice_gui.exe from the Releases tab on the right.

How to Use - CLI

Run it from a terminal. This gives a bit more control over ICE.

openice.exe <in.dng> [out.dng] [options]

Option	Meaning
-o <out.dng>	Output path. Defaults to <in>.openice.dng; a bare second argument works too.
-order <RGBI>	Channel order of the source samples (default RGBI); the 4th letter marks the IR channel. Set this if your DNG stores the channels in a different order.
-dpi <N>	Override the source resolution instead of reading it from the DNG.
-lowres <file>	A low-resolution scan of the same frame, used to calibrate ICE. If omitted, openICE down-samples the main scan instead — visually close, but not bit-exact.
-lowres_fields <V>	The three calibration values directly, as irCrosstalk,Rref,irRefRaw (comma-separated). When given, used instead of a low-res scan.
-fine	Use ICE Fine instead of the default Normal (see parameters).
-kind <7|8|9>	Scanner reconstruction target: 8 = LS-5000 (default), 7 = LS-9000, 9 = LS-50 (see parameters).

To Get Started

Requirements

• 64-bit Windows with the .NET Framework 4.x runtime (already installed on Windows 10 / 11).
• An RGBI scan saved as a DNG — either interleaved (VueScan's "48/64-bit RGBI") or with the infrared in a separate plane (SilverFast). Both little- and big-endian DNGs are read and written.
• Modest memory: the pipeline streams row by row, so even a full 24 MP frame stays well under a gigabyte.

Download the latest openice.exe from this repo's Releases tab.

Build

Both builds use the C# compiler csc from the .NET Framework — it ships with Windows at C:\Windows\Microsoft.NET\Framework64\v4.0.30319\csc.exe. Add that folder to PATH (or call csc by its full path), and run the commands from the openICE directory.

CLI — openice.exe

Every source except the WinForms front-end (openice_gui.cs):

csc /platform:x64 /optimize+ /out:openice.exe `
    src\openice.cs src\IcePump.cs src\IceSetup.cs src\IceRow.cs src\IceFront.cs `
    src\IceBack.cs src\IceCore.cs src\IceBuffers.cs src\IceAnalyze.cs src\dng.cs

GUI — openice_gui.exe

Adds the WinForms front-end and the DPI-awareness manifest (src\*.cs picks up every file; /main selects the GUI entry point):

csc /platform:x64 /target:winexe /main:OpenIceGui /out:openice_gui.exe `
    /r:System.Windows.Forms.dll /r:System.Drawing.dll `
    /win32manifest:src\app.manifest src\*.cs

Nikon Scan 4 vs openICE

See VALIDATION.md.

Input	From Nikon Scan	openICE w/ Low-Res	openICE w/o Low-Res

Project Layout

src/
  openice.cs     CLI: RGBI DNG in → clean RGB DNG out
  IcePump.cs     the per-row streaming driver
  IceAnalyze.cs  the low-res calibration pass (crosstalk + IR-ref → irCrosstalk, IRref)
  IceSetup.cs    Phase 0: density LUT, geometry, per-scan constants
  IceBuffers.cs  the ring / plane / staging buffers (original buffer allocator, transliterated)
  IceRow.cs      Phase 1: per-row ring slot-advance + frame reset
  IceFront.cs    Phase 2: the 6 front-half builders
  IceBack.cs     Phase 3: reconstruction driver + v/L build + output convert
  IceCore.cs     the soft-threshold reconstruction core + dither/LCG helpers + Sdc state
  dng.cs         DNG read/write (RGBI DNG in, 3-channel RGB DNG out)
src_C/           the byte-exact C port of src. See src_C/README.md

openICE pipeline

flowchart LR
  RAW(["<b>RGBI scan</b>"]) --> D["<b>§1 · density convert</b><br/>RGBI → log-density d"]
  LOW(["<b>low-res prescan</b>"]) --> CAL["<b>§2 · calibration</b><br/>get clean IR-base color<br/>and how much red bleeds IR"]
  D -. "d" .-> G["<b>§3 · IR gate g</b><br/>strip the dye crosstalk<br/>isolate dust"]
  CAL -. "c, IR_ref" .-> G
  G -. "g" .-> W["<b>§4 · clean-confidence weight</b><br/>w(g)∈[0,1]"]
  W --> DEC{"<b>§5 · give up<br/>or reconstruct?</b>"}
  DEC -->|"already clean / unreconstructable"| CP["<b>give up</b><br/>copy input through"]
  DEC -->|reconstruct| P["<b>§6 · convolution pyramids</b><br/>calculate with surrounding pixel values"]
  P -. "P, C, L" .-> CORE["<b>§7 · reconstruction core</b><br/>reconstruct pixel with clean neighboring pixels"]
  CORE --> DI["<b>§8 · dither</b><br/>add film grain on reconstructed pixels"]
  DI --> O["<b>§9 · output</b><br/>density → 16-bit RGB"]
  CP --> O
  O --> RES(["<b>clean RGB</b>"])

  classDef calib fill:#dcfce7,stroke:#16a34a,color:#14532d;
  class LOW,CAL calib;

Loading

See Pipeline

Why do I need Low-Res Scan for ICE?

Nikon Scan's Digital ICE requires an initial low-res scan to calculate three calibration values. Specifically, they are:

Values	Meaning
irCrosstalk	Dye→IR crosstalk: the fraction of the visible (red) signal that bleeds into the IR channel. Subtracted from IR so the dust gate reacts only to dust and scratches, not to the picture.
Rref	The visible (red) reading of clear film — an IR-weighted average over dust-free areas. The baseline the crosstalk term corrects for.
irRefRaw	The infrared reading of clear film — the same IR-weighted average. The "no-dust" IR level, before the crosstalk correction.

However, we found that using a down-sampled image of the main scan still gives visually good performance. By default, openICE uses a down-sampled image as the low-res scan. See VALIDATION.md.

TODO

• macOS support

License

openICE is free software, licensed under the GNU General Public License v3.0 — see LICENSE. You may use, study, modify, and redistribute it; if you distribute a modified version, it must also be GPL-3.0 and carry its source.

Copyright (C) 2026 <a6o>

Trademarks & Disclaimer

openICE is an independent, unofficial reimplementation created for interoperability and research. It is not affiliated with, endorsed by, or sponsored by Nikon, Kodak, Applied Science Fiction, or any other company whose products it interoperates with.

All product names, logos, and brands are the property of their respective owners:

• Digital ICE is a trademark of Eastman Kodak Company (the technology was originally developed by Applied Science Fiction).
• Nikon, Coolscan, and Nikon Scan are trademarks of Nikon Corporation.
• VueScan is a trademark of Hamrick Software; SilverFast is a trademark of LaserSoft Imaging AG.
• Adobe and DNG are trademarks of Adobe Inc.

These names are used only for identification and descriptive purposes (nominative fair use) and do not imply any association with, or endorsement by, the trademark holders.