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 PGX format. This tool works for both professionals and casual users. Convert your images to PGX 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.
JPEG 2000 VM Uncompressed
A single-component test format for JPEG 2000 verification.
PGX is an extremely simple, uncompressed raster format created specifically for the development and testing of the JPEG 2000 standard (ISO 15444). It is defined in the JPEG 2000 Verification Model (VM). Its purpose is to store a single component (channel) of an image with potentially high bit depth and signed/unsigned values, without the complexity of a full image container.
A PGX file represents one image channel (grayscale). It starts with a minimalist text header identifying the endianness (`LMS` or `Big`), the sign (`+`/`-`), the bit depth, and dimensions. The raw pixel data follows immediately. It is effectively a raw dump of a single image plane.
Developed by the JPEG committee during the creation of JPEG 2000. It allowed researchers to test wavelet compression algorithms on raw data without worrying about file headers or color transforms.
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