PGM vs PPM
PPM stores three RGB samples per pixel without compression or alpha. It is easy to inspect in processing pipelines, but sacrifices compactness and rich metadata; select it when direct sample interchange is the priority.
Image format
PGM
Portable Graymap: simple uncompressed raster samples for image-processing pipelines.
Explore the format
Convert PGM to
Choose a target format for your PGM images.
JPEGJPEGPGM → JPEGPNGPNGPGM → PNGWebPWebPPGM → WebPAVIFAVIFPGM → AVIFHEICHEICPGM → HEICHEIFHEIFPGM → HEIF
All 21 conversions
Marked paths may need steps such as flattening, rasterization, tone mapping or animation loss.
Convert to PGM
Choose a source format to convert to PGM.
JPEGJPEGJPEG → PGMWith caveatPNGPNGPNG → PGMWith caveatWebPWebPWebP → PGMWith caveatAVIFAVIFAVIF → PGMWith caveatHEICHEICHEIC → PGMWith caveatHEIFHEIFHEIF → PGMWith caveat
All 36 conversions
GIFGIFGIF → PGMWith caveatTIFFTIFFTIFF → PGMWith caveatBMPBMPBMP → PGMWith caveatSVGSVGSVG → PGMICOICOICO → PGMWith caveatJPEG XLJPEG XLJPEG XL → PGMWith caveatJPEG 2000JPEG 2000JPEG 2000 → PGMWith caveatQOIQOIQOI → PGMWith caveatTGATGATGA → PGMWith caveatPCXPCXPCX → PGMWith caveatPPMPPMPPM → PGMWith caveatPBMPBMPBM → PGMWith caveatPAMPAMPAM → PGMWith caveatHDRHDRHDR → PGMWith caveatEXREXREXR → PGMWith caveatPSDPSDPSD → PGMWith caveatPDFPDFPDF → PGMWith caveatDNGDNGDNG → PGMWith caveatCanon CR2Canon CR2Canon CR2 → PGMWith caveatCanon CR3Canon CR3Canon CR3 → PGMWith caveatCanon CRWCanon CRWCanon CRW → PGMWith caveatNikon NEFNikon NEFNikon NEF → PGMWith caveatSony ARWSony ARWSony ARW → PGMWith caveatFujifilm RAFFujifilm RAFFujifilm RAF → PGMWith caveatOlympus ORFOlympus ORFOlympus ORF → PGMWith caveatPanasonic RW2Panasonic RW2Panasonic RW2 → PGMWith caveatPentax PEFPentax PEFPentax PEF → PGMWith caveatSigma X3FSigma X3FSigma X3F → PGMWith caveatKodak RAWKodak RAWKodak RAW → PGMWith caveatHasselblad 3FRHasselblad 3FRHasselblad 3FR → PGMWith caveat
Marked paths may need steps such as flattening, rasterization, tone mapping or animation loss.
About PGM
Portable Graymap
PGM is Netpbm’s simple grayscale raster format. It stores one intensity sample per pixel instead of RGB components. A header declares width, height and maximum sample value. This makes grayscale images easy to exchange between small programs without needing a palette or a general-purpose colour container.
P2 represents samples as text; P5 uses binary samples, one or two bytes according to maxval, up to 65535. Data is uncompressed and there is no separate alpha channel. The manual also describes an opacity-mask variant; a grayscale image and a mask can use the same storage but have different meanings.
Use PGM for grayscale processing and explicit single-channel masks. Document whether samples represent intensity, opacity or application data. Colour conversion to PGM removes chromatic information and requires a chosen grayscale mapping; increasing the sample precision later cannot recover removed colours or tonal values.
Key capabilities
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.
History of PGM
This format belongs to the documented Pbmplus/Netpbm evolution. The history distinguishes the original bitmap idea, later channel models and library development.
PGM compared
Different formats, different trade-offs. Choose for the image and the workflow.
PGM vs PBM
PBM stores only black and white, one bit per pixel in its binary form. It fits bitonal masks and line art; tonal images need thresholding or dithering, so gradients cannot remain as continuous gray levels.
PGM vs PAM
PAM extends Netpbm with explicit tuple types and depths, including RGB_ALPHA and GRAYSCALE_ALPHA. It suits channel-aware processing, but receiving tools must agree on the tuple meaning and it remains uncompressed.
PGM vs PNG
PNG preserves decoded pixels losslessly and can carry alpha. It is useful for transparent graphics and screenshots; it does not preserve editable document layers or camera sensor data, and photographic files can be large.
PGM FAQ
What does this format store?
PGM is Netpbm’s simple grayscale raster format. It stores one intensity sample per pixel instead of RGB components. A header declares width, height and maximum sample value. This makes grayscale images easy to exchange between small programs without needing a palette or a general-purpose colour container.
How does compression affect quality?
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.
Is a PGM mask an alpha channel?
It can be interpreted as an opacity mask by agreement, but the file contains only one channel. It does not combine grayscale image pixels with a separate alpha channel as PAM GRAYSCALE_ALPHA can.
What should I check before opening the file?
Check the magic number, sample precision and tuple or channel meaning. Many simple readers accept only one binary image and 8-bit samples even though the specifications permit more.
What changes when I export to another format?
Preserve maxval and colour interpretation when creating the rendered output. Grayscale and bitonal targets remove information deliberately; alpha requires an alpha-bearing tuple or a separate mask. Optional comments may not transfer.
When is this format useful?
Use PGM for grayscale processing and explicit single-channel masks. Document whether samples represent intensity, opacity or application data. Colour conversion to PGM removes chromatic information and requires a chosen grayscale mapping; increasing the sample precision later cannot recover removed colours or tonal values.