PGM to EXR: conversion guide

What happens when you convert PGM to EXR?

Multiple source images

PGM can contain multiple image representations with different roles. These are not automatically a timed animation. Selecting an image, preserving a collection or creating several outputs needs explicit engine support; neither a first-image choice nor an all-images export is implemented.

No new colour information

The source stores grayscale or bitonal values. A colour-capable EXR can represent these tones, but conversion cannot infer original scene colours or recover missing intermediate shades. Colourisation would be a separate image-editing operation.

An HDR container adds no captured range

EXR can hold HDR working or display values, but exporting an SDR image does not reconstruct clipped highlights or missing shadow detail. Numeric conversion, colour space and transfer function depend on the future engine. A wider container is not an automatic HDR enhancement.

Encoding mode

EXR supports lossy and lossless codecs. Choose one for the sample types and required precision; .exr alone does not guarantee exact channel preservation. EXR permits different encoding modes or container representations. Its format name alone does not promise lossless output, a quality setting or a size reduction. The future engine must choose a supported codec and sample representation; inspect the target’s compression notes below.

PGM

Source

PGM

Portable Graymap

Compression: UncompressedTransparency: NoMetadata: Header, Comments

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

Explore PGM format →

EXR

Target

EXR

OpenEXR

Compression: Lossy & losslessTransparency: YesMetadata: Typed header attributes, Chromaticities

HDR raster data for rendering and compositing, with named channels and lossless or lossy codecs.

Explore EXR format →

Is PGM → EXR right for you?

Good choice when

EXR fits your delivery use: Render passes & HDR compositing.
You can choose the source image or part needed for delivery.
You need the existing gray or binary image in a compatible delivery format.
You need an image in an HDR-capable working pipeline.
You need a EXR-compatible workflow that can hold transparency added in a separate edit.

Probably not when

You require a complete collection, page set or multipart round trip.
You expect automatic colourisation or reconstruction of absent tones.
You expect new highlight or shadow detail from a container change.
You need a guaranteed quality or file size before encoder settings exist.
You expect automatic background removal or transparency.

PGM to EXR conversion details

Multiple source images: PGM can contain multiple image representations with different roles. These are not automatically a timed animation. Selecting an image, preserving a collection or creating several outputs needs explicit engine support; neither a first-image choice nor an all-images export is implemented.
No new colour information: The source stores grayscale or bitonal values. A colour-capable EXR can represent these tones, but conversion cannot infer original scene colours or recover missing intermediate shades. Colourisation would be a separate image-editing operation.
An HDR container adds no captured range: EXR can hold HDR working or display values, but exporting an SDR image does not reconstruct clipped highlights or missing shadow detail. Numeric conversion, colour space and transfer function depend on the future engine. A wider container is not an automatic HDR enhancement.
Transparency: The target can store an alpha channel, but converting an opaque image does not create transparent areas. Removing a background is a separate editing step.
Encoding mode: EXR supports lossy and lossless codecs. Choose one for the sample types and required precision; .exr alone does not guarantee exact channel preservation. EXR permits different encoding modes or container representations. Its format name alone does not promise lossless output, a quality setting or a size reduction. The future engine must choose a supported codec and sample representation; inspect the target’s compression notes below.
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: PGM: Uncompressed → EXR: Lossy & lossless 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. EXR: EXR supports lossy and lossless codecs. Choose one for the sample types and required precision; .exr alone does not guarantee exact channel preservation.
Transparency: PGM: No → EXR: Yes
Colour depth: PGM: maxval up to 65535 → EXR: HALF 16 / FLOAT 32 / UINT 32
HDR: EXR: Floating-point working values
Multiple images: EXR: Multipart
Dimensions: Pixel dimensions, page geometry, rendering resolution, resizing and orientation need explicit converter policies. The future engine has not defined them yet.
Metadata: PGM: Header, Comments → EXR: Typed header attributes, Chromaticities. Which fields are copied, rewritten or omitted will depend on the future engine; retention is not implemented yet.

Common questions

Will every source image be exported?

PGM can contain multiple image representations with different roles. These are not automatically a timed animation. Selecting an image, preserving a collection or creating several outputs needs explicit engine support; neither a first-image choice nor an all-images export is implemented.

Can conversion restore colour or missing shades?

The source stores grayscale or bitonal values. A colour-capable EXR can represent these tones, but conversion cannot infer original scene colours or recover missing intermediate shades. Colourisation would be a separate image-editing operation.

Can EXR recover clipped highlights?

EXR can hold HDR working or display values, but exporting an SDR image does not reconstruct clipped highlights or missing shadow detail. Numeric conversion, colour space and transfer function depend on the future engine. A wider container is not an automatic HDR enhancement.

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?

PGM: Header, Comments → EXR: Typed header attributes, Chromaticities. Which fields are copied, rewritten or omitted will depend on the future engine; retention is not implemented yet.

Explore related PGM and EXR conversions.