Over PGM-bestanden

PGM (PGM Grayscale Image · Afbeeldingsformaat)

Uitgebracht 1988 Door Jef Poskanzer

PGM Grayscale Image (.pgm) is een standaard bestandsformaat dat door KaijuConverter wordt ondersteund voor gegevensuitwisseling, archivering en platformonafhankelijke conversie.

Categorie

Raster & Vector Images

Extensie

.pgm

MIME-type

image/x-portable-graymap

Bruikbaar als

Invoer Uitvoer

Het verhaal

HOE PGM
IS ONTSTAAN.

PGM — Portable GrayMap — is the grayscale sibling of PBM and PPM in Jef Poskanzer’s 1988 Netpbm toolkit. Where PBM stores 1-bit black-or-white pixels, PGM stores 8-bit (values 0-255) or 16-bit (0-65535) grayscale values. Like its sibling formats, PGM comes in ASCII (P2) and binary (P5) variants, and shares the same stupidly simple header: magic number, width, height, max value, then pixel data.

PGM has been the Unix grayscale intermediate format since shell pipelines needed one. OCR engines (Tesseract) preprocess scanned documents to PGM before recognition. Medical imaging pipelines convert DICOM images to PGM for ImageMagick processing. Machine-vision and photogrammetry tools exchange depth maps as 16-bit PGM. It’s a format that refuses to die because its simplicity is its best feature.

WEETJES &
TRIVIA.

Tesseract OCR's preferred input format is PGM — every "scan to text" pipeline on Linux preprocesses through it.

Medical imaging workflows use 16-bit PGM to preserve the 12-bit output of X-ray and MRI scanners during intermediate processing.

A grayscale photo compresses 8× better as a 1-bit PBM if you dither it — but loses all tonal detail.

Machine-vision systems exchange depth maps as 16-bit PGM because the single-channel grayscale fits depth values naturally.

The P2 (ASCII) and P5 (binary) magic numbers are the only difference between two structurally identical file variants.

STERKE PUNTEN &
BEPERKINGEN.

Sterke punten

Trivially simple to parse and generate.
Ideal Unix pipeline intermediate for grayscale processing.
Preserves 16-bit depth for scientific and medical data.
Universal tooling (Netpbm, ImageMagick, Tesseract).
ASCII variant is human-readable.

Beperkingen

No compression — files balloon for large images.
No metadata, no color profile.
Grayscale only — drop to PBM for bitmap or up to PPM for color.
Not a delivery format — strictly pipeline intermediate.

Typische bestandsgroottes

1920×1080 grayscale 8-bit (binary P5)

~2 MB

1920×1080 grayscale 16-bit

~4 MB

DICOM-equivalent medical slice

500 KB - 20 MB

Technische specificaties

MIME type: image/x-portable-graymap
Extension: .pgm
Variants: P2 (ASCII), P5 (binary)
Bit depth: 8-bit or 16-bit per pixel
Creator: Jef Poskanzer (1988), Netpbm toolkit

CONVERTEER VANUIT
PGM

pgm jpg pgm png pgm webp pgm avif pgm gif pgm bmp pgm tiff pgm ico pgm pdf

Veelvoorkomende toepassingen

Scientific imaging, machine vision