There is of course no substitute for the genuine tools or descriptions from the equipment vendors themselves, and pointers to helpful individuals in various organizations, as well as names and catalog numbers of various useful documents, are included here where known. In addition there are several small companies that specialize in such connectivity problems that have a good reputation and are well known. Contact information is provided for them, though I personally have no experience with their products and am not endorsing them. Finally, great care has been taken not to include any information that has been released under binary option tricks-disclosure agreements.
What is included here is the result of either information freely released by vendors, handy hints from others working in the field, or in many cases close scrutiny of hex dumps and experimentation with scanner parameters and study of the effects on the image files. Please use this information in the spirit in which is intended, and where possible contribute whatever you know in order to expand the information to cover more vendors and equipment. Extracting the image information alone is usually straightforward and is described in 1. NEMA style of data stream, which, though never intended as a file format per se has proven useful as model. NEMA dumping program to see what it contains. If you see even group tags, they will be described in the standard. NEMA based SPI format padded out to 512 bytes.
131072 bytes of pixel data at the end of the file. 4X files are for example, then you need to skip 14336 bytes of header before you get to the data. This tool is something that is sadly lacking in most commercial image handling programs for non-medical applications, which can’t import images with more than 8 bits per channel. Occasionally one runs into clever files where four 12 bit words are packed into three 16 bit words and one goes crazy trying to figure out the logic of how they are packed.
NEMA standard describes somewhere one way in which this is done. One should still be able to calculate the length easily enough. Of course the GE CT 9800 uses perimeter encoding even when DPCM compression is not selected, so this technique won’t work. NEMA Standards Publication PS2-1989, was released which described various means fo extending standard 300-1985 to handle compression utilizing a broad range of reversible and irreversible schemes. NEMA SP 300-1988 which are summarized briefly here. Section 6 describes command structure which is not really relevant other than that commands are also structured in the same way as data and consume part of the data dictionary. A message consists of a series of “data elements” each of which contains a piece of information.
The data stream is ordered by ascending group number, and within each group by ascending data element number. Each element may occur only once in a message. Even numbered groups describe elements defined by the standard. The values may be single or multiple. It is of length 0000000C hex or 12 bytes long.