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Viewer Controls

Relay provides a rich set of viewer controls tailored to the type of file you’re viewing. Each pane has fully isolated viewport state, so adjustments in one pane don’t affect others.

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Image adjustments

These controls are available for all image types in two tabs:

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Basic tab

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Color tab

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Channel controls (scientific images)

For multi-channel images (OME-TIFF, Zarr), the scientific controls panel provides per-channel editing:
  • Visibility toggle — eye icon to show/hide individual channels
  • Color picker — click the color swatch to assign a LUT color to any channel
  • Intensity histogram — interactive SVG histogram with draggable min/max handles for display range
  • Gamma handle — optional mid-tone adjustment on the histogram
  • Auto-contrast — automatically calculate p1/p99 percentile display range per channel from real histogram data
  • Channel split mode — split channels across separate panes, each showing one channel
The histogram supports 8-bit (256 bins) and 12-bit (4096 bins) data, with log-scale display and pointer/keyboard navigation.

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Image metadata

A collapsible metadata section shows:
  • Dimensions (width x height x channels x Z-slices x time-points)
  • Bit depth, file size, format
  • Pixel scale / physical size (used for scale bar)

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Z-stack navigation

For multi-plane images:
  • Z-slice slider with debounced scrubbing (100ms)
  • Play/pause animation with configurable FPS (default 2 FPS)
  • Step forward/backward buttons
  • Open in 3D button — splits a new pane and loads the same image in the volume viewer
  • Z-stack export — export selected Z-range

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Time-series navigation

For time-lapse images, use the time slider to scrub through time points.

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Keyboard navigation

  • Arrow keys — advance Z-slice or time-point
  • Shift + Arrow keys — advance by 10 steps
  • Delete / Backspace — delete selected annotation or clear loaded image

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Camera controls

  • Pan — click and drag with the hand tool, or hold middle mouse button
  • Zoom — scroll wheel, or use the zoom buttons in the toolbar
  • Fit to view — double-click the zoom controls to fit the image to the pane
  • Camera linking — link pan/zoom across multiple panes so they move in sync. Click the link icon in the pane header.

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Minimap

A bird’s-eye overview of the full image with a viewport rectangle. Click to navigate. Toggle via right-click context menu or the minimap icon. Setting persists per-pane.

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Scale bar

Toggle the scale bar overlay for images with physical pixel size metadata. Shows in the bottom-right corner.

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Image layers (multi-image overlay)

Overlay multiple images in a single pane by holding Alt while dropping a file:
  • Up to 8 image layers per pane
  • Per-layer controls: opacity (0–100%), visibility toggle, blend mode, z-order
  • Reorder layers with move-up/move-down buttons
  • Each layer has independent channel overrides
  • Focus a layer to make it the active editing target
The Image Layer panel appears in the sidebar when a pane has 2+ layers.

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Toolbar tools

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Region selection tools

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Context menu (right-click)

  • Add Image to Deck — capture the current viewport as a card
  • Show Minimap — toggle the bird’s-eye overview

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Volume 3D viewer

When viewing Z-stacks, click Open in 3D to open the volume renderer in a new pane:

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DICOM-specific controls

When viewing DICOM files, adjustments map to DICOM-standard window/level:
  • Window/Level presets — dropdown with anatomy presets (Lung, Bone, Brain, etc.)
  • Brightness = Window Center / Contrast = Window Width
  • Series selector — switch between DICOM series in multi-series studies
  • DICOM invert — toggle MONOCHROME1/MONOCHROME2
  • Supports both single files and multi-slice folders

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Video playback controls

When viewing video files:
  • Play/Pause — start or stop playback
  • Skip — jump forward or backward
  • Frame slider — scrub to any frame
  • Speed selector — adjust playback speed
  • Frame counter — current frame number display
  • Videos auto-pause when you select an annotation tool, so you can annotate individual frames

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Spike viewer controls

For electrophysiology data (NWB, H5, SpikeGLX .bin+.meta files):
  • Waveform viewer — extracted spike waveforms
  • Power spectrum — frequency domain analysis
  • Detail channel — zoomed view of individual channels
  • Amplitude scatter — spike amplitude distributions
  • Correlogram — cross-correlogram between units
  • ISI histogram — inter-spike interval distribution (linear or log scale)
  • Template viewer — average waveform templates per unit
  • Sorting tabs — view and navigate sorting results