DNG to PGM: conversion guide

What happens when you convert DNG to PGM?

RAW development

DNG needs camera- and file-aware development to produce a rendered PGM image. White balance, exposure, camera colour interpretation and, where applicable, demosaicing determine that rendering. The destination does not retain the original RAW development latitude. No development settings or camera support are implemented yet.

Grayscale output

PGM stores one grayscale sample per pixel, with no colour channels or alpha. Colour input becomes gray; brightness depends on the colour transform and transfer-function handling chosen by the future engine. Higher maxval can retain more gray levels, but does not retain chromatic information.

Lossless sample storage

Netpbm stores these samples without compression. Reducing colour, thresholding or changing maxval can still lose information before storage; text and binary representations change the layout, not its image meaning. PGM can store its supported image samples without lossy compression. This applies after rendering and sample conversion: it does not guarantee preservation of source precision, colour space or document structure, and cannot undo earlier losses.

DNG

Source

DNG

Adobe Digital Negative

Compression: Depends on variantTransparency: NoMetadata: Exif, DNG tags

A published TIFF-based format for raw image data, calibration and photographic metadata.

Explore DNG format →

PGM

Target

PGM

Portable Graymap

Compression: UncompressedTransparency: NoMetadata: Header, Comments

Portable Graymap: simple uncompressed raster samples for image-processing pipelines.

Explore PGM format →

Is DNG → PGM right for you?

Good choice when

PGM fits your delivery use: Grayscale images & masks.
You need a developed image for a non-RAW application.
Your processing pipeline explicitly needs grayscale samples.
You need lossless storage of the rendered samples supported by PGM.

Probably not when

You need the original sensor data and freedom to redevelop it.
Colour distinctions carry information you need to retain.
You expect lossless encoding to restore lost details or editing structure.
You require identical samples without a defined colour and precision policy.

DNG to PGM conversion details

RAW development: DNG needs camera- and file-aware development to produce a rendered PGM image. White balance, exposure, camera colour interpretation and, where applicable, demosaicing determine that rendering. The destination does not retain the original RAW development latitude. No development settings or camera support are implemented yet.
Grayscale output: PGM stores one grayscale sample per pixel, with no colour channels or alpha. Colour input becomes gray; brightness depends on the colour transform and transfer-function handling chosen by the future engine. Higher maxval can retain more gray levels, but does not retain chromatic information.
Lossless sample storage: Netpbm stores these samples without compression. Reducing colour, thresholding or changing maxval can still lose information before storage; text and binary representations change the layout, not its image meaning. PGM can store its supported image samples without lossy compression. This applies after rendering and sample conversion: it does not guarantee preservation of source precision, colour space or document structure, and cannot undo earlier losses.
Sample precision & colour: Source and target sample models can differ in precision, channel layout, colour space and transfer function. Lossless compression only preserves the samples actually encoded; a precision reduction or colour conversion can already change them. The future engine defines numeric mapping, orientation and colour conversion; canonical depth facts are listed below where available.
Metadata & colour: Format support does not guarantee that an export preserves metadata or colour profiles. Retention and colour handling depend on the future converter; its engine is not implemented yet.
Compression: DNG: Depends on variant → PGM: Uncompressed DNG: Compression, sample type and processing stage are defined by the file and DNG version. Converting a proprietary raw file to DNG is different from exporting a rendered photo, but it does not guarantee preservation of every maker-specific feature. Keep the source when future reprocessing or vendor software matters. PGM: Netpbm stores these samples without compression. Reducing colour, thresholding or changing maxval can still lose information before storage; text and binary representations change the layout, not its image meaning.
Colour depth: DNG: File-defined sample precision → PGM: maxval up to 65535
Sensor data: DNG: Raw development required
Dimensions: Pixel dimensions, page geometry, rendering resolution, resizing and orientation need explicit converter policies. The future engine has not defined them yet.
Metadata: DNG: Exif, DNG tags → PGM: Header, Comments. Which fields are copied, rewritten or omitted will depend on the future engine; retention is not implemented yet.

Common questions

Will PGM still be an editable camera RAW?

DNG needs camera- and file-aware development to produce a rendered PGM image. White balance, exposure, camera colour interpretation and, where applicable, demosaicing determine that rendering. The destination does not retain the original RAW development latitude. No development settings or camera support are implemented yet.

Will PGM keep the source colours?

PGM stores one grayscale sample per pixel, with no colour channels or alpha. Colour input becomes gray; brightness depends on the colour transform and transfer-function handling chosen by the future engine. Higher maxval can retain more gray levels, but does not retain chromatic information.

Does lossless output mean an unchanged source?

Netpbm stores these samples without compression. Reducing colour, thresholding or changing maxval can still lose information before storage; text and binary representations change the layout, not its image meaning. PGM can store its supported image samples without lossy compression. This applies after rendering and sample conversion: it does not guarantee preservation of source precision, colour space or document structure, and cannot undo earlier losses.

Are bit depth and colour values guaranteed to match?

Source and target sample models can differ in precision, channel layout, colour space and transfer function. Lossless compression only preserves the samples actually encoded; a precision reduction or colour conversion can already change them. The future engine defines numeric mapping, orientation and colour conversion; canonical depth facts are listed below where available.

Will metadata and colour profiles be retained?

DNG: Exif, DNG tags → PGM: Header, Comments. Which fields are copied, rewritten or omitted will depend on the future engine; retention is not implemented yet.

Explore related DNG and PGM conversions.