Here are a few lines about the "BIFF" file format, the format used in the XITE system. XITE - X-based Image processing Tools and Environment - is a free system from dept. of informatics, university of Oslo, Norway. The format is quite simple, and I see no point in describing it in detail, but I would like to mention a few features that we are satisfied with. First of all, the format is only 3D (unfortunately, it should be N-dim.). It defines an image to be a sequence of 2D bands. Every band may have its own size and pixel type, which even allows the pyramide representation to be used. There are also separate parameters for positioning and magnification of each band. Any amount of ascii text may also be stored on the same file. The whole structure is read from file in one call, and represented in one data structure, something like (in C): IMAGE i; i = read_image(filename); Then the image i may be asked for number of bands: fprintf("Number of bands: %d\n", nbands(i)); It may also be indexed: fprintf("Pixel value: %d\n", i[band][y][x]); The bands may be handled separately: BAND b; b = i[1]; /* pointer to first band */ fprintf("Size of band: %d x %d\n", xsize(b), ysize(b)); fprintf("Pixel value: %d\n", b[y][x]); The data structures represent pixel values as well as corresponding information, thus only one parameter must be transferred to functions. The format defines a number of pixel types, but most functions are only implemented for the byte pixel type. The function can test the arriving band to see if it has correct pixel type, something like: if (pixeltype(b) != unsigned_byte) ... A final feature is the sub-band mechanism. A sub-band is a _pointer_ to a rectangular subset of a band. When transferred to a function, the function does not have to distingwish between "normal" bands, and sub-bands. To negate some rectangular part of a band b1: BAND b2; b2 = sub-band(b1, x1, x2, y1, y2); /* define the rectangular subset of b1 */ negate(b2, b2); /* two parameters because in general different input and output are used, in this case identical parameters are allowed. If b1 is now displayed, we see that the subset is negated. */ To conclude: the file format allows some important flexibility (different size and pixel type in each band), and it is very easy to write programs using the format, as a "memory-format" is, defined and the neccessary functions are written. I will be glad to answer any questions. Sincerely, Tor Lonnestad Dept. of Informatics University of Oslo Norway e-mail: tor@ifi.uio.no