yacomp

Yet Another Comparison Viewer — a userscript for side-by-side screenshot comparison on tracker and image-hosting sites.

yacomp gives comparison pages a consistent fullscreen viewer across different sites: hover to switch sources, navigate rows from the keyboard, zoom and pan, and apply visual filters to inspect compression artifacts, luma/chroma differences, brightness drift, and gamma mismatches.

Supported sites

Integration style	Sites
Detect screenshot grids and viewer galleries	HDB
Replace the native viewer	PTP, BLU, ATH, BHD, GPW, SSD, FRDS
Add a viewer button	slow.pics, comp.pics

Install & usage

Install a userscript manager such as Tampermonkey or Violentmonkey, then click here to install the latest release.

• On HDB torrent pages, detected comparison grids get a Show comparison link. Other screenshot groups get a compact Show Viewer control placed directly above the image run, and image clicks open the same gallery viewer by default. If a block is ambiguous, Show Viewer includes a column-count dropdown: 1 opens it as a gallery, while 2+ builds a manual comparison; a non-divisible image count leaves the final row short.
• On HDB forum pages it also adds a Custom comparison builder below the page title, for markup too irregular to auto-detect safely (see Features).
• On native-viewer sites, use the site's comparison UI as usual; yacomp takes over when the viewer opens.
• On slow.pics / comp.pics it adds a native-style button — and the V key — that opens the current comparison in yacomp.

Features

• Consistent comparison viewer — open any supported comparison in the same fullscreen UI, regardless of the site's native presentation.
• HDB screenshot gallery viewer — torrent screenshots that are not safe comparisons get a local Show Viewer control and also open in the same viewer from an image click, so image-host thumbnails, saved pages, and sample galleries do not fall back to tiny native previews.
• Fast source & row navigation — hover to switch sources by horizontal position, plus arrow / vim / number keys for sources and rows.
• Zoom & pan — fit, 1:1, incremental zoom, Ctrl + wheel cursor-centered zoom, drag panning, a minimap, and a row-navigation sidebar.
• Visual filters — Solar ×1 / ×2, Residual, Luma, and Chroma modes for artifact and channel inspection.
• Per-source adjustments — brightness, contrast, and gamma-mismatch checks (sRGB ↔ BT.1886, the 0.88 AE/QuickTime fix, Legacy Mac) for the selected source only.
• Colorspace-aware luma/chroma — BT.709 / BT.2020 handling from URL hints or PNG/JPEG ICC profile data when available.
• Custom comparison builder (HDB forums) — when markup is too irregular for safe auto-detection, build a comparison by hand. Click or drag across screenshots to select a gallery (Shift to extend, Ctrl/⌘-click to toggle one). Name the columns by clicking a source label or selecting text; Ctrl/⌘-click more labels to add columns, with each pick highlighted on the page. Pick the column count from the dropdown — lock it to rotate names within a fixed count instead of adding more — and turn on grouped by source when the poster stacked each source's shots in its own block rather than interleaving them. The toolbar floats while you select and stays up after a build so you can adjust and rebuild.
• Customizable shortcuts — rebind any action to a key (modifiers included) or a mouse button from the settings panel; each action takes a main binding plus an optional second one.
• Shortcuts help overlay — press ? (or the toolbar button) for a live keyboard legend that reflects your current bindings.
• Per-site toggles — turn any integration off without uninstalling, to fall back to a site's native viewer.
• Lazy loading — rows load on demand, with optional background loading and automatic syncing for dynamically added (lazy / SPA) images.

Chrome / Edge note: a browser GPU bug can render the visual filters slightly off (filtered images look a touch dark). To avoid it for now, disable hardware acceleration — Settings → System → "Use graphics acceleration when available" → off, then relaunch.

Shortcuts

Every shortcut is rebindable in yacomp Settings; the defaults are:

Key	Action
V	Open the yacomp viewer on a slow.pics / comp.pics page
F / Shift+F	Cycle visual filter forward / backward
[ / ]	Decrease / increase brightness for the current source
{ / }	Decrease / increase contrast for the current source
G / Shift+G	Cycle gamma-mismatch check forward / backward
\ / Shift+\	Reset adjustments for the current source / all sources
+ / -	Zoom in / out
Ctrl + wheel	Cursor-centered zoom
0	Fit to width
O	Actual size (1:1)
C	Toggle canvas fill / fit
H / L or ← / →	Previous / next source
K / J or ↑ / ↓	Previous / next row
1–9	Jump to source number
M	Toggle minimap
R	Toggle row-navigation sidebar
B	Toggle background loading
?	Toggle the shortcuts help overlay
Esc	Reset active adjustments, or close the viewer

Configuration

Open the settings panel from the userscript manager menu (yacomp Settings). Settings persist via GM_setValue and are scoped per userscript manager.

Viewer defaults

• Initial zoom mode (Fit / 1:1) — whether the viewer opens scaled to fit the viewport or at native 1:1 pixels. Default 1:1.
• Zoom indicator base (Original / Fit) — what 100% in the zoom HUD refers to. Original = source's native pixels; Fit = scaled-to-viewport. Default Original.
• Verbose zoom info — when on, the zoom toast adds pixel counts and viewport callouts; when off, it's a single-line percentage label. Default off.
• Fill canvas by default — whether each row fills the viewport (cropping) or fits inside it (letterbox) at open. Toggle later with C. Default off (fit).
• Minimap by default — whether the thumbnail navigation minimap is on at open. Toggle later with M. Default on.
• Background loading by default — when on, all rows start downloading at open rather than waiting for lazy-load. Toggle later with B. Default off.
• Hover to switch source — when on, moving the cursor across a row switches the visible source by horizontal position; when off, switching needs the keyboard or source menu. Default on.
• Close button position (Auto / Left / Right) — Auto places it on the left on macOS and on the right elsewhere, matching native window controls.

Adjustments

• Brightness / contrast step — the increment per [ / ] and { / } press. Range 0.01–0.25, default 0.05.
• Toast duration — how long a HUD toast stays visible. Range 500–10000 ms, default 2000 ms.
• Zoom scale factor — the multiplier per + / - press (1.25 = ±25% per step). Range 1.05–2.0, default 1.25.
• Lazy-load margin — how far outside the visible area, in CSS pixels, deferred rows start downloading. Measured against the viewer's scroll container, not image size, so the number of rows covered shifts with zoom. Range 0–2000 px, default 200 px.

Shortcuts

Rebind any action to a key (with modifiers) or a mouse button. Click a field, then press the key or mouse button to capture it; Esc cancels and a duplicate binding is rejected. Each action needs a main binding; the optional extra (e.g. arrow and vim keys) can be cleared with ×.

Sites

A per-site toggle for every supported integration (HDB, PTP, BLU, ATH, BHD, GPW, SSD, FRDS, slow.pics, comp.pics). Disabling a site stops yacomp from injecting there without an uninstall.

• HDB image click (Viewer / Native) — controls what happens when clicking HDB comparison or gallery thumbnails. Viewer opens yacomp at that image; Native leaves the original HDB/image-host link behavior alone. This does not remove the Show comparison / Show Viewer controls. Default Viewer.

Filter cycle

Pick which visual filters are reachable via F / Shift+F, and drag to reorder them. Unchecked filters are skipped; the list order is the cycle order.

Gamma cycle

Pick which gamma-mismatch presets are reachable via G / Shift+G, and drag to reorder them. Same skip-and-order behavior as the filter cycle.

Storage and migration

A schema version is stored alongside the config; older payloads are migrated forward on first load, and unknown or out-of-range values fall back to the built-in defaults.

Development

The project uses Bun and TypeScript. The built userscript is written to dist/yacomp.user.js.

bun install
bun run build            # Build dist/yacomp.user.js
bun run watch            # Rebuild when src/ changes
bun run typecheck        # Type-check without emitting files
bun run typecheck:tests  # Type-check tests and Playwright config
bun run verify           # Sanity-check the generated userscript
bun run test             # Run unit tests
bunx playwright install chromium  # Install local browser for e2e tests
bun run test:e2e         # Run Playwright viewer tests
bun run fixture          # Serve the local viewer fixture
bun run check            # typecheck + build + verify
bun run clean            # Remove dist/

Core code lives in src/: sites/ contains site adapters, viewer/ the fullscreen comparison UI, filters/ the zoom / colorspace / visual-filter logic, and shortcuts/ the bindable action registry. Userscript metadata and URL matches live in meta/banner.txt.

For new site support, parse the page into the shared grid model and reuse the existing viewer rather than adding site-specific viewer behavior.

Unit tests live in tests/unit. Playwright e2e tests live in tests/e2e and use the local fixture in tests/fixtures/viewer, so viewer controls can be tested without external network access.

CI runs type-checking, build verification, unit tests, and the e2e suite on pushes and pull requests targeting main. Releases are tag-driven: pushing a v* tag builds and uploads dist/yacomp.user.js.

License

MIT