Image format
The PBM format
PBM is a pure black-and-white image format, one bit per pixel. PBM is the one-bit member of the 1988 Netpbm family, originally for fax-style black-and-white images.
When to use PBM
Use PBM for black-and-white line art headed into a tracer, a plotter or an OCR tool.
It is best for line art, fax-style scans and input for tracing and OCR tools, and it opens on GIMP, ImageMagick, potrace and OCR tools — not browsers or phones.
How to open it: GIMP, ImageMagick and macOS Preview open PBM files.
| Full name | Portable Bitmap |
|---|---|
| Extensions | .pbm |
| MIME type | image/x-portable-bitmap |
| Introduced | 1988 |
| Compression | Uncompressed |
| Transparency | No |
| Animation | No |
| Support | Specialist format |
| Typical size | Width × height ÷ 8 bytes |
Good at
- Tiny for simple black-and-white images
- Ideal input for vector tracing
Not so good at
- Every pixel is either black or white, so photos turn into stark silhouettes
- Unsupported by everyday apps
The common mistake
Photos converted to PBM lose all shading. Use a threshold that suits the picture, or dithering, or you get a black blob.
Questions
What is a PBM file?
PBM (Portable Bitmap) is a pure black-and-white image format, one bit per pixel. PBM is the one-bit member of the 1988 Netpbm family, originally for fax-style black-and-white images.
How do I open a PBM file?
GIMP, ImageMagick and macOS Preview open PBM files.
How do I make a PBM file?
Open the Image Converter, drop your file and choose PBM. It converts in your browser, so nothing is uploaded.