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 PCX images to FAX format. This tool works for both professionals and casual users. Convert your images to FAX in seconds.
Picture Exchange
The de facto standard for DOS paint programs.
PCX (Picture Exchange) was one of the first widely accepted standards for DOS imaging. Created by ZSoft for their PC Paintbrush software, it became the native format for Windows 3.0 Paintbrush and supported the evolution of PC graphics hardware from monochrome CGA to 256-color VGA and eventually 24-bit TrueColor.
PCX uses a header containing the version, dimensions, and palette information, followed by image data compressed using a simple Run-Length Encoding (RLE) scheme. This scheme was very efficient for the simple graphics of the 80s (large areas of flat color) but is poor for complex photographs. 256-color palettes are often appended at the end of the file.
Established in 1985. It enjoyed a decade of dominance before being displaced by BMP (on Windows), GIF (on the web), and JPEG (for photos). It is now largely obsolete but still recognized by many tools due to its historical significance.
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.
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