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 JNG format. This tool works for both professionals and casual users. Convert your images to JNG 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 Network Graphics
JPEG compression with PNG transparency.
JNG (JPEG Network Graphics) is a sub-format of the MNG animation format. It was designed to combine the high compression of JPEG with the alpha transparency features of PNG, something that standard JPEG lacks. It essentially wraps a JPEG stream and a mask channel in a chunk-based container.
A JNG file structure mimics PNG. It uses a 8-byte signature and chunks. The image data is split into a color chunk (JDAT) which contains JPEG data, and an alpha chunk (IDAT) which contains PNG-compressed alpha mask. This allows for 'lossy color, lossless alpha' images, which is very space-efficient for photographic sprites.
Created by the PNG Development Group around 2001 as part of the MNG (Multiple-image Network Graphics) project. It failed to gain traction as MNG was rejected by Mozilla and Chromium in favor of APNG and later WebP.
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