ImageToIcon

ImageToIcon is a small cross-platform tool for turning any image into a multi-size Windows .ico file. Drop in a single picture and it generates all the standard icon sizes at once, with clean Lanczos downscaling — no wizard, no upsell, no bundle of proprietary editors.

Every icon workflow used to mean juggling three tools: one to resize, one to compose, one to export. ImageToIcon collapses that into one window and one save button.

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Preview (light / dark)

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Features

• Runs natively on Linux and Windows — same binary logic, same output
• Load any common raster format: PNG, JPEG, BMP, TIFF, GIF, WebP, TGA, QOI, PBM/PGM/PPM/PNM
• Automatic generation of every standard Windows icon size from 8 px up to 512 px
• Toggle individual sizes on or off before saving — the default preset matches the classic Windows application icon set (256, 128, 64, 48, 32, 24, 16)
• High-quality Lanczos-3 resampling for sharp results at every size
• Replace individual sizes manually — swap in a hand-tuned image for 16 px or 32 px and it gets resized in place to fit the slot
• Drag-and-drop support on the main window and on individual thumbnails
• CLI mode for batch conversion and scripting — process a folder of images in one call
• PNG-compressed frames inside the ICO container for smaller files, especially at 256 px and up

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Download

The latest release is available on the Releases page — no installation required, just extract and run the executable — ImageToIcon.exe on Windows, ImageToIcon on Linux.

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Command Line

ImageToIcon also runs headless. Any invocation containing --cli (or /cli) skips the UI and processes files directly:

ImageToIcon --cli --o=./out image1.png image2.jpg
ImageToIcon --cli --o=./out --sizes=16,32,48,256 logo.png
ImageToIcon --cli --o=./out --sizes=all logo.png

Option	Description
--cli, /cli	Run in CLI mode.
--o=DIR, /o=DIR	Output directory for the generated .ico files.
--sizes=<list>	Comma-separated list of icon sizes to generate.
--sizes=all	Generate every supported size.
--help, /?	Show usage information.

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Requirements

Linux

• Any modern x64 Linux distribution
• No .NET runtime required — ships as a self-contained single-file executable

Windows

• Windows 10 or later (x64)
• No additional dependencies — ships as a self-contained single-file executable

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Building from Source

Prerequisites

• .NET 10 SDK

Build

# Debug build (default, linux-x64 only)
./build.sh

# Release build (linux-x64 and win-x64)
./build.sh Release

Run directly (without full build)

cd src/ImageToIcon
dotnet run