Dynapik offers a free online tool to change image types - no need to download anything. It's quick and easy to use. You can change your FAX images to PBM format. This tool works for both professionals and casual users. Convert your images to PBM in seconds.
Group 3 FAX
The raw compressed data stream used by classic fax machines.
When we talk about the 'FAX' file format, we typically refer to a raw data stream compressed using the CCITT Group 3 (G3) or Group 4 (G4) algorithms. These are specialized compression methods designed for bi-level (black and white) images of text documents. In most modern contexts, you won't see a standalone `.fax` or `.g3` file. Instead, this compression data is wrapped inside a container like TIFF or PDF. A `.fax` file is essentially a headerless chunk of this compressed data, which makes it difficult for modern software to open without knowing the specific dimensions (width/height) beforehand.
Group 3 compression is based on Huffman coding and Run-Length Encoding (RLE). It scans a line of pixels and records the lengths of alternating runs of black and white pixels. Because most documents are largely white space, this results in significant compression. Group 4 is an improvement that uses 2D compression (referencing the previous line to predict the next), offering better ratios but requiring an error-free transmission channel (like a digital network), unlike G3 which had to survive noisy phone lines.
Standardized by the CCITT (Consultative Committee for International Telephony and Telegraphy), now ITU-T, in 1980 (Group 3) and 1984 (Group 4). These standards enabled the global fax boom of the 80s and 90s.
Portable Bitmap
The lowest common denominator of image formats.
PBM (Portable Bitmap) is the simplest format in the Netpbm suite, designed to represent monochrome (black and white) images. It uses a straightforward text-based (or simple binary) encoding where '1' represents black and '0' represents white (or vice versa depending on the viewer, though standard entails 1=black). It was designed to be easily emailed and processed by simple scripts.
There are two variants: P1 (ASCII) and P4 (Binary). ASCII P1: The file is human-readable text. A grid of 0s and 1s defines the image. Binary P4: The bits are packed into bytes for efficiency. The header simply states the magic number (P1 or P4) and the dimensions. There is no compression, no index, no palette.
Invented by Jef Poskanzer in the 1980s as a way to send bitmaps via email properly. It became the foundation of the 'pbmplus' (later 'netpbm') toolkit, which provided a standard way to convert between dozens of incompatible 80s file formats.
Experience lightning-fast image conversions with our advanced algorithms. No more waiting for your files to be uploaded before processing.
Enjoy unlimited image conversions without any hidden fees. Our service is completely free to use, with no limitations on file size or quantity.
Convert images files between over 20 formats. We support popular formats like PNG, JPG, WebP, HEIC and more.
Use Dynapik on any device with a modern browser. We support all major platforms such as Windows, macOS, Linux, Android, and iOS.
Ensure high fidelity in your conversions. Our professional-grade output is ideal for designers, marketers, and content creators.
Your files are safe with us. We focus on your privacy and security with advanced encryption and local processing.