Spectra Swift

A native macOS viewer for spectroscopy files: JCAMP-DX, the format the NIST WebBook serves for IR, mass, and UV-Vis spectra, and Bruker OPUS files straight from the spectrometer. Built with Swift and SwiftUI.

Drop a .jdx, .dx, or OPUS .0 file onto the window (or double-click it in Finder) and you get an interactive plot that follows the conventions chemists expect: IR spectra draw with the wavenumber axis running high to low, mass spectra draw as stick plots, and a toolbar toggle converts IR data between transmittance and absorbance on the fly.

Screenshots

Three NIST gas-phase IR spectra overlaid on a normalized axis:

Peak picking on benzene, with the picked peaks marked on the plot and listed in the results table below:

A Coblentz Society spectrum shown on its native wavelength axis, with every parameter from the file in the searchable inspector:

Features

• Overlay and compare - Load any number of spectra; checkboxes in the sidebar control which ones draw together. Spectra with different y-units overlay on a normalized axis.
• Navigate - Rubber-band box zoom, scroll-wheel and pinch zoom about the cursor, Option-drag to pan, double-click or ⌘0 to reset.
• Read values - A crosshair snaps to the nearest data point on any visible trace and shows its exact coordinates.
• Measure - Pick peaks by hand or detect them automatically, measure baseline-referenced peak heights, and integrate the area between two points. Results land in a table you can copy into Excel or export as CSV.
• Label peaks - Picked peaks are labeled on the plot, and you can rename any label in the results table ("C-H stretch" beats "3086.2"). Labels carry into exported images and the peak table.
• Smooth - A Savitzky-Golay filter with a live preview cleans up noisy instrument data. The result appears as a new spectrum; the original data is never touched.
• Open instrument files - Bruker OPUS files (.0, .1, ...) open directly, including the processed spectrum and instrument metadata.
• Difference spectra - Subtract one spectrum from another to spot what changed.
• Sessions - Save your whole workspace (files, colors, measurements, view) as a .spectrasession file and pick up where you left off.
• Inspect metadata - Every parameter recorded in the file, in a searchable panel, along with any warnings from parsing.
• Export - CSV or JCAMP-DX for the data; PNG or vector PDF for the plot; ⇧⌘C copies the plot straight to the clipboard.

Requirements

• macOS 14.0 (Sonoma) or later

Installing

1. Download SpectraSwift-<version>.zip from the latest release
2. Unzip it and drag Spectra.app into your Applications folder
3. Open it. Releases from 1.1.2 on are signed and notarized, so macOS opens them like any other app.

After that the app keeps itself current: it checks for updates once a day, and you can check any time with Spectra Swift ▸ Check for Updates. Updates install and relaunch in place.

One quirk worth knowing: OPUS files use bare numeric extensions (.0, .1), which other apps sometimes claim. If double-clicking one doesn't open Spectra Swift, right-click it and choose Open With once.

Known issues

• Dragging the sidebar divider to the right can leave the spectra list looking blank. Nothing is lost; toggle the sidebar closed and open again (View ▸ Hide/Show Sidebar, ⌃⌘S) and it comes back. (#1)
• The sidebar occasionally starts hidden after a restart; the same shortcut brings it in. (#2)
• Files opened while the app is closed occasionally don't load; open the file again once the app is running. (#3)
• Measuring is deliberately disabled while a spectrum is displayed unit-converted or on a mixed-unit normalized overlay. Show the spectrum by itself to measure it in its native units.

Format support

The parser handles the JCAMP-DX 4.24/5.00 features found in real-world files: (X++(Y..Y)) data with the full ASDF compression set (PAC, SQZ, DIF, DUP), peak tables, NTUPLES data tables, compound multi-spectrum files, and both line-abscissa conventions in circulation (including the one NIST's quantitative IR database uses). Malformed files degrade gracefully: recoverable oddities load with a warning badge instead of failing, and unreadable files produce a clear error naming the reason.

Bruker OPUS binary files import their processed result spectrum (absorbance or transmittance, detected from the file), the x grid, and every instrument, sample, and acquisition parameter for the inspector. Interferograms and raw single-channel data are skipped; a file holding only those says so instead of guessing. The reader was validated against reference implementations and tested on files straight off a working spectrometer.

Parsing lives in SpectraKit, a UI-free Swift package, and is tested against fixtures downloaded from NIST as well as synthetic edge cases.

Building

Requires macOS 14+, Xcode 16 or later, and XcodeGen.

xcodegen generate
xcodebuild -project Spectra.xcodeproj -scheme Spectra -configuration Debug build

Or open the generated Spectra.xcodeproj in Xcode and run.

To run the library tests:

swift test

Layout

Sources/SpectraKit/   file parsing and the spectrum model (no UI)
Tests/                Swift Testing suite + NIST fixture files
App/                  the SwiftUI app
project.yml           XcodeGen project definition

Planned

Normalizing spectra to a reference peak, friendlier handling of Raman files (they currently draw with the IR axis convention), and reading the instrument-parameter blocks that some ATR files use, so the inspector fills in for those too. Ideas and bug reports welcome in the issues.

License

MIT License - see LICENSE