OpenQuad

Warning

Beta: work in progress. OpenQuad 0.1.0 beta 3 is an early test release. It works on the hardware it was developed with (a Canon PIXMA MG3600 and its built-in scanner), but it hasn't been tried widely yet. Expect rough edges, and please report what you find.

Open-source black-and-white and toned inkjet printing, and digital negatives for carbon transfer, in the spirit of QuadToneRIP. OpenQuad calibrates an ordinary inkjet printer with its own scanner so greys print neutral and evenly spaced, adds optional duotone toning, and makes UV-blocking digital negatives with process calibration (ChartThrob-style charts) for contact printing.

It comes as a Mac app (beta) and as a Python command-line tool and desktop app, which share calibration files and settings.

Download the beta (Mac app)

1. Download OpenQuad-0.1.0b3.zip (or the newest) from the latest pre-release and unzip it.
2. Move OpenQuad.app to your Applications folder.
3. The beta isn't notarized by Apple yet, so the first time you open it macOS will refuse. Open it anyway: double-click it once, then go to System Settings ▸ Privacy & Security and click Open Anyway next to OpenQuad. Or, in Terminal: xattr -dr com.apple.quarantine /Applications/OpenQuad.app

The first time you scan, macOS asks to let OpenQuad find devices on your local network: choose Allow (it talks to your printer's scanner). If you chose Don't Allow, turn OpenQuad on in System Settings ▸ Privacy & Security ▸ Local Network, then quit and reopen it.

Needs macOS 14 (Sonoma) or later, on Apple silicon or Intel. A short How to Use OpenQuad guide opens on first launch (and later from Help or the ? button).

What to try

• Print a photo: open a photo, leave toning neutral or choose a duotone, and print through the macOS print panel or straight to a printer. Does the print match the preview, and come out at the size it says?
• Calibrate your printer, if it has a network (AirScan / eSCL) scanner: Calibrate This Printer… prints a test page, scans it and corrects colour casts and tone. How many rounds did it take, and did the goals get met?
• Digital negatives: make a negative and try the blocking test and process calibration, if you contact print (carbon, or another UV process).
• Contact sheets: the Contact Sheet tab (⌘3) puts up to 16 photos on one sheet, to print or to make a negative of.
• Darkroom marks: the guide line and registration marks (Darkroom marks, in the Print and Negative tabs and both calibration wizards). Can you see and line up a red or orange negative under your safelight?
• Tabs: Print, Negative, Contact Sheet, Printer Calibration and Process Calibration each keep their own work. Does moving between them while working feel natural?
• The guide: is anything unclear or missing?

Reporting problems

Use the beta feedback form. Say which Mac, macOS version, printer and paper you used, and attach a screenshot or scan if it helps. The app keeps its calibration runs, scans and measurements in ~/Library/Application Support/OpenQuad, which you can zip up and attach as well.

Known limitations

• Not notarized: see the install steps above.
• Tested hardware: a Canon PIXMA MG3600 (Letter, plain paper) and its scanner; an Epson ET-2900's scanner works since beta 3 (its calibration is in progress). Other printers should work through the macOS print panel or CUPS. Scanning needs an eSCL scanner on the network; any scanner works through "Read a Scan File".
• Print panel vs lp: the Canon calibration was made printing straight to the printer (lp). A calibration made through the macOS print panel should be used through the panel (the wizard records which, and the app matches it).
• Carbon: the process calibration has been checked on simulated prints and the blocking test on real carbon prints, but not a full process calibration on real tissue yet.
• QuadToneRIP-style raw-ink printing (per-ink channels through Gutenprint) isn't built yet. The beta prints through the normal printer driver.

Status

Part	State
Mac app (SwiftUI): print window, toning, digital negatives, print panel or direct printing	beta
Printer calibration wizard (grey balance, tone), calibration library per printer	beta, tested on Canon MG3600
Blocking test and process calibration wizards (carbon)	beta, partly tested
Python CLI and desktop app (PySide6)	working; the reference implementation
Raw-ink QuadToneRIP-style path	not built

Hardware results: docs/hardware-tests.md. Calibration data from real prints and scans: calibration-data/. Mac app details: swift/README.md. Screenshots: docs/screenshots/.

Python tools (command line and desktop app)

uv sync --extra ui
uv run openquad-app          # the PySide6 desktop app
uv run openquad --help       # the command line

Usage

openquad target -o wedge.tif                       # 21-step greyscale wedge, 300 dpi
openquad presets                                   # list colour-layer presets
openquad composite photo.tif -o toned.tif --preset black-red
openquad printers                                  # CUPS printer names
openquad print toned.tif --printer Canon_MG3600_series --dry-run
openquad print photo.tif --printer Canon_MG3600_series --preset black-red

Grey balance for a colour inkjet (example: Canon MG3600 on plain paper):

openquad target --kind grey-balance -o gb.tif
openquad print gb.tif --printer Canon_MG3600_series
openquad scan --host 876298000000.local -o scan.jpg       # face down; Document mode by default
openquad measure scan.jpg -o m1.json
openquad greybalance m1.json -o canon-plain.oqcal --printer Canon_MG3600_series --paper "Letter plain"
openquad print photo.tif --printer Canon_MG3600_series --preset black-red --calibration canon-plain.oqcal

To check and refine, print a comparison page (uncorrected and corrected targets on one sheet), scan it once, and measure both:

openquad target --kind comparison --calibration canon-plain.oqcal -o compare.tif
openquad measure scan2.jpg --pair --calibration canon-plain.oqcal -o m2.json
openquad greybalance m2-corrected.json -o canon-plain-v2.oqcal --shadow-damping 0.5

Once grey balance is good, even out the tone from the same kind of measurement:

openquad linearize m3-corrected.json --calibration canon-plain-v3.oqcal          # report only
openquad linearize m3-corrected.json --calibration canon-plain-v3.oqcal -o canon-plain-v4.oqcal

A calibration is only valid for the printer, paper and driver settings it was made with.

print prints at the file's real size (its DPI) on Letter paper by default; use --paper, --ppi, --copies and --option NAME=VALUE (driver options) to change that.

Digital negatives (carbon printing)

Print negatives on inkjet-coated transparency film (plain or laser film won't hold the ink):

openquad target --kind blocking -o blocking.tif      # 1. which ink colour blocks the UV?
openquad print blocking.tif --printer Canon_MG3600_series
#    expose it on carbon tissue at your usual time, make the print, scan it:
openquad scan --host 876298000000.local -o carbon.jpg
openquad blocking carbon.jpg                          #    -> which colours block, and their range
openquad negative photo.tif -o neg.tif --colour green --fit Letter   # 2. a negative in that colour

The orientation F in the safe edge prints in the carbon print: if it reads backwards, flip --mirror.

Red and orange negatives are hard to see under a red safelight: --guide adds a black line round the image and --registration adds targets and corner crop marks, all in black ink in the safe edge (it blocks UV like the safe edge, so they don't print). Test sheets take --size WxH to fit your tissue:

openquad negative photo.tif -o neg.tif --colour orange --fit Letter --guide --registration
openquad target --kind blocking --size 5x7 --guide -o blocking.tif

Then calibrate the process from a ChartThrob-style chart (after Kevin Bjorke's ChartThrob):

openquad target --kind chart --colour green -o chart.tif     # print on film, contact print, scan
openquad chart carbon-chart.jpg -o carbon.oqproc               # build the process curve
openquad target --kind chart --process carbon.oqproc -o chart2.tif   # check: print, scan, read
openquad chart carbon-chart2.jpg --process carbon.oqproc -o carbon-v2.oqproc
openquad negative photo.tif -o neg.tif --process carbon-v2.oqproc --fit Letter

The curve evens out patch-to-patch noise (--smoothing none|light|medium|strong, default medium), and the report warns when tones are lost: highlights printing as paper white or shadows as full black, which no curve can bring back. To make negatives in other software, as with ChartThrob, export the curve, apply it to the greyscale photo there and invert:

openquad curve carbon-v2.oqproc carbon.acv       # Photoshop Curves (up to 16 points)
openquad curve carbon-v2.oqproc carbon.amp       # Photoshop arbitrary map (exact, 256 levels)
openquad curve carbon-v2.oqproc carbon.cube      # 3D LUT; or .csv for the 257 levels
openquad curve carbon-v2.oqproc curved.tif --image photo.tif   # the photo with the curve applied

Contact sheets

Up to 16 photos as thumbnails on one greyscale sheet, which then prints like any photo (or becomes a negative):

openquad contact-sheet frames/*.tif -o sheet.tif --size 7.5x10 --wedge --labels
openquad negative sheet.tif -o sheet-neg.tif --colour green --fit Letter

--background white, --crop (fill every cell) and --gap INCHES change the layout.

Development

uv sync
uv run pytest
uv run ruff check . && uv run mypy
uv run pre-commit install --hook-type pre-commit --hook-type pre-push
swift test --package-path swift/OpenQuadCore     # the Swift core, checked against Python
swift test --package-path swift/OpenQuadApp      # the Mac app
swift/sign-app.sh                                # build swift/build/OpenQuad.app

The Swift core is matched against the Python reference with test vectors (scripts/export_swift_vectors.py); CI runs both on every push.

Licence

GPL-2.0-or-later. See LICENSE. OpenQuad is not affiliated with QuadToneRIP.