whoshue

A pixel-art color analyzer for KDE/Wayland. Capture a game/application window, select part of its preview, and inspect the captured colors. The analyzer is a normal desktop window; it does not flash calibration colors or hide itself.

Run

On CachyOS/Arch with KDE, the capture backend uses xdg-desktop-portal, xdg-desktop-portal-kde, and PipeWire. Building needs Rust, a C toolchain, pkgconf, Clang/libclang, and PipeWire development libraries (libpipewire).

cargo run --release
# Or start with a local image, without requesting screen sharing:
cargo run --release -- /path/to/screenshot.png

1. Click Choose source…. KDE handles selecting a window, screen, or region. Click it again to choose a different source.
2. Drag a rectangle in the source preview. Capture display pauses during the drag, then returns to its previous live/frozen state. The crop is stored in source pixels and resets if the source dimensions change.
3. Freeze holds the displayed frame and analysis; Resume takes the newest available frame. Stop sharing closes capture and keeps the last image.
4. Inspect the nearest-neighbor zoomed crop. Hover for source coordinates, RGB/hex and HSV; click to copy hex. Click palette swatches to copy them too.
5. Save crop PNG writes a uniquely named PNG in the system temporary directory and displays its path. Drop an image or click Open image… to browse for a file in KDE's file picker.

The HSV histogram has 36 ten-degree bins. Switch between pixel counts and equal weight per distinct RGB color. Colors with saturation below 5% are counted separately as neutrals. The palette is exact (no quantization), ordered by count, then RGB for deterministic ties. Fully transparent pixels are excluded; partially transparent pixels retain their stored RGB values and count once.

Choosing a source always opens KDE's picker. The last portal token is saved at $XDG_CONFIG_HOME/whoshue/config.toml (normally ~/.config/whoshue/config.toml) for the command-line capture diagnostic. No capture starts until Choose source… is clicked. Cancelling the file picker leaves the current image/capture unchanged.

Portal requests share one application-lifetime async runtime. PipeWire runs on a separate blocking worker so restarting capture or opening another portal dialog cannot strand the cached D-Bus connection on a stopped executor.

Limits and next work

• Window capture is preferred: screen/region capture includes overlapping windows, including whoshue if placed inside the captured area.
• Selection follows coordinates within the source, not a moving sprite.
• Analysis uses source pixels before preview scaling, but these are rendered colors, not necessarily original game-asset colors. HDR and color-profile conversion have not been validated; the current path assumes ordinary SDR RGB.
• Live analysis refreshes at most five times per second. Large selections with many unique colors are more expensive; release builds are recommended.
• Game-specific behavior on focus loss/minimization needs desktop testing.
• Perceptual OKLCH views, color/hue highlighting, and comparing saved selections are future features; this first version uses HSV.

Validation

cargo test --offline --locked
cargo clippy --offline --locked --all-targets -- -D warnings
cargo fmt --check

Tests cover hue boundaries, neutral/transparent pixel handling, weighting, cropping, selection coordinates, pixel-format conversion, frozen-frame behavior, resize handling, headless UI rendering, file-picker cancellation/reopening, and repeated portal requests during/after capture. The portal regression test requires dbus-run-session and permission to create a local socket; it uses its own private bus and does not open desktop dialogs. Actual portal capture requires a running Wayland desktop and permission through KDE's picker.

For a capture-only diagnostic (saves the first full source frame):

cargo run -- --selftest /tmp/whoshue-selftest.png