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
• Exports Windows ICO, macOS ICNS and Linux hicolor icon trees (as folder or .tar.gz archive)
• Load any common raster format: PNG, JPG, BMP, DIB, TIF, GIF, WEBP, TGA, QOI, PBM/PGM/PPM/PNM
• Load SVG files directly (rasterised via Skia) and extract icon frames straight from ICO, ICNS, EXE and DLL files
• Default preset covers the standard Windows application icon sizes (256, 48, 32, 24, 16); separate defaults for ICNS and hicolor
• Freely add, edit or remove custom sizes — any value from 2 px up to 4096 px, right-click a size to manage it
• High-quality Lanczos-3 resampling for sharp results at every size
• Corner radius slider — round the icon from soft corners all the way to a full circle mask
• Padding slider — shrink the content inside the frame to taste
• Background color picker with an eyedropper to sample from any existing thumbnail
• Shadow effect with color, X/Y offset and blur, optionally wrapping the background
• Stroke effect with color, width and an inner/outer offset slider, optionally wrapping the background
• Testing mode — preview icons flat, and strip the background from the saved file in one click
• Per-thumbnail fit mode (Fit, Stretch or Crop) with mouse-wheel zoom and right-click drag to pan
• Any size can use its own source image — drop a hand-tuned 16 px or 32 px onto that slot and it is used only for that size, while all others keep rendering from the main image
• Drag-and-drop support on the main window and on individual thumbnails
• CLI mode exposing the full set of shape, background and effect options for batch conversion and scripting
• Settings persist between sessions — selected sizes, formats, corner, padding, shadow and stroke
• PNG-compressed frames inside the ICO and ICNS containers 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 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

Run ImageToIcon --help to see the full list of options, including format, corner, padding, background and effect flags.

Option	Description
--cli	Run in CLI mode.
--o=DIR	Output directory.
--name=NAME	Output base name (default: input file name). Single input only.
--format=ico|icns|hicolor	Output format (default: ico).
--hicolor-archive	Write hicolor as .tar.gz instead of a folder.
--sizes=<list>	Comma-separated icon sizes (2–4096).
--corner=0..1	Corner radius (0 = square, 1 = full circle).
--padding=0..1	Padding fraction.
--fit=fit|stretch|crop	Fit mode (default: fit).
--bg=#RRGGBB[AA]	Background color.
--shadow=#RGBA,offX,offY,blur	Shadow — offsets and blur as fraction of size.
--stroke=#RGBA,width[,offset]	Stroke — width fraction, offset 0..1.
--shadow-no-bg	Shadow ignores background (only with --bg).
--stroke-no-bg	Stroke ignores background (only with --bg).
--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

Other platforms (untested)

Self-contained binaries for linux-arm64 and win-arm64 are published alongside the main releases via ./build.sh Release full. They are built from the same source and should work, but they are not actively tested — please report back if you try them.

macOS is reachable via ./build.sh Release all, which additionally produces osx-x64 and osx-arm64 binaries. These are raw Mach-O executables, not .app bundles, so they are only usable from the terminal. Wrapping the output in a minimal ImageToIcon.app/Contents/MacOS/ layout with an Info.plist is straightforward. Open an issue if you want a signed .app build.

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Building from Source

Prerequisites

• .NET 10 SDK

Build

The script takes two optional arguments: configuration (Debug | Release) and scope (minimal | standard | full | all). Both default to the first option.

Scope	Runtimes
minimal	linux-x64
standard	linux-x64, win-x64
full	linux-x64, linux-arm64, win-x64, win-arm64
all	Like full plus osx-x64, osx-arm64 (raw binaries, no .app bundle)

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

# Release build, linux-x64 only
./build.sh Release

# Release build, linux-x64 and win-x64
./build.sh Release standard

# Release build, all four runtimes (linux-x64, linux-arm64, win-x64, win-arm64)
./build.sh Release full

# Release build, everything including macOS (osx-x64, osx-arm64)
./build.sh Release all

Run directly (without full build)

cd src/ImageToIcon
dotnet run