DNGForge

Non-destructive RAW editor for DNG files, in the style of Lightroom/Camera Raw: white balance, tone curve, saturation/sharpness, radial and graduated filters, spot removal, lens correction, crop/straighten, undo/redo, EXIF metadata panel, filmstrip gallery.

Why: a zero-cost alternative to a Lightroom subscription, not an alternative to Adobe as a technology. DNGForge writes edits into the real Adobe crs XMP tags (Adobe DNG Converter is free, unlike Lightroom) — a file processed here, opened in real Lightroom, comes out practically identical and still fully editable, and vice versa. No external sidecar files: saving always and only writes inside the DNG itself.

How it works

Every pixel shown or saved is rendered by Adobe DNG Converter, a required runtime dependency: DNGForge.pyw only builds the editing XMP tags and hands them to the converter — it never touches pixels directly.

One exception: the three local-adjustment tools — radial filter, graduated filter and spot removal — aren't rendered by Adobe DNG Converter (unsupported by its CLI), so for those three tools only, the app composites pixels locally (OpenCV/Pillow) on top of Adobe's own render.

Requirements

• Python 3.10+ and the dependencies in requirements.txt (pip install -r requirements.txt)
• Adobe DNG Converter installed at the standard Windows path
• a real exiftool binary (not just the library) version ≥ 12.15

Running

pythonw DNGForge.pyw [file.dng]

The (optional) argument loads a DNG on startup.

Main features

• White balance: color picker on the raw sensor data, presets, colorimetric temperature/tint
• Custom tone curve, saturation, sharpness
• Radial and graduated filters, multi-region, with Lightroom/ACR-compatible XMP persistence
• Spot removal
• Lens correction (via lensfunpy)
• Crop and straighten
• Undo/redo (20-state stack) + revert to last save
• EXIF metadata panel, filmstrip gallery to browse a folder
• Copy/paste settings between photos
• RGB histogram

Structure

• DNGForge.pyw — main application (a single DNGForge(QMainWindow) class)
• backups/ — significant earlier versions, kept for reference
• reference/ — third-party code consulted as reference (not included in the repo)