miff



NAME

     MIFF - Magick Image File Format is a platform-independent
     format for storing bitmap images.  MIFF is a part of the
     ImageMagick toolkit of image manipulation utilities for the
     X Window System.  ImageMagick is capable of converting many
     different image file formats to and from MIFF (e.g. JPEG,
     XPM, TIFF, etc.).


SYNOPSIS

     #include <image.h>


DESCRIPTION

     A MIFF image file consist of two sections.  The first
     section is a header composed of keywords describing the
     image in text form.  The next section is the binary image
     data.  The header is separated from the image databy a :
     character immediately followed by a newline.

     The MIFF header is composed entirely of ASCII characters.
     The fields in the header are keyword and value combination
     in the keyword=value format, with each keyword and value
     separated by an equal sign (=).  Each keyword=value
     combination is delimited by at least one control or
     whitespace character.  Comments may appear in the header
     section and are always delimited by braces.  The MIFF header
     always ends with a colon (:) character, followed by a
     newline character.  It is also common for a formfeed and a
     newline character to appear before the colon. You can then
     list the image keywords with more(1), without printing the
     binary image that follows the colon separator.

     The following is a list of keyword=value combinations that
     may be found in a MIFF file:

     class=DirectClass
          class=PseudoClass indicates the type of binary image
          data stored in the MIFF file.  If this keyword is not
          present, DirectClass image data is assumed.

     colors=value
          specifies the number of colors in a DirectClass image.
          For a PseudoClass image, this keyword specifies the
          size of the colormap.  If this keyword is not present
          in the header, and the image is PseudoClass, a linear
          256 color grayscale colormap is used with the image
          data.

     columns=value
          indicates the width of the image in pixels.  This is a
          required keyword and has no default.

     compression=RunlengthEncoded
          compression=QEncoded indicates the type of algorithm
          used to compress the image data.  If this keyword is
          not present, the image data is assumed to be
          uncompressed.

     id=ImageMagick
          The id keyword identifies the file as a MIFF-format
          image file.  This keyword is required and has no
          default.  Although this keyword can appear anywhere in
          the header, it should start as the first keyword of the
          header in column 1.  This will allow programs like
          file(1) to easily identify the file as MIFF.

     matte=True
          matte=False specifies whether a DirectClass image has
          matte data.  Matte data is generally useful for image
          compositing.  This keyword has no meaning for pseudo-
          color images.

     montage=<width>x<height>{+-}<x offset>{+-}<y offset>
          size and location of the individual tiles of a
          composite image.  See X(1) for details about the
          geometry specification.

     Use this keyword when the image is a composite of a number
     of different tiles.  A tile consists of an image and
     optionally a border and a label.  <width> is the size in
     pixels of each individual tile in the horizontal direction
     and <height> is the size in the vertical direction.  Each
     tile must have an equal number of pixels in width and equal
     in height.  However, the width can differ from the height.
     <x offset> is the offset in number of pixels from the
     vertical edge of the composite image where the first tile of
     a row begins and <y offset> is the offset from the
     horizontal edge where the first tile of a column begins.

     If this keyword is specified, a directory of tile names must
     follow the image header.  The format of the directory is
     explained below.

     packets=value
          specifies the number of compressed color packets in the
          image data section.  This keyword is optional for
          RunlengthEncoded images, mandatory for QEncoded images,
          and not used for uncompressed image.

     rows=value
          indicates the height of the image in pixels.  This is a
          required keyword and has no default.

     scene=value
          indicates the sequence number for this MIFF image file.
          This optional keyword is used when a MIFF image file is
          one in a sequence of files used in an animation.

     signature=value
          this optional keyword contains a string that uniquely
          identifies the image colormap.  Unique colormap
          identifiers are normally used when animating a sequence
          of PseudoClass images.

     The following is a sample MIFF header.  In this example,
     <FF> is a formfeed character:

         id=ImageMagick
         class=PseudoClass  colors=256
     signature=d79e1c308aa5bbcdeea8ed63df412da9
         compression=RunlengthEncoded  packets=27601
         columns=1280  rows=1024
         scene=1
         {
           Rendered via Dore by Sandi Tennyson.
         }
         <FF>
         :

     Note that keyword=value combinations may be separated by
     newlines or spaces and may occur in any order within the
     header.  Comments (within braces) may appear anywhere before
     the colon.

     If you specify the montage keyword in the header, follow the
     header with a directory of image tiles.  This directory
     consists of a name for each tile of the composite image
     separated by a newline character.  The list is terminated
     with a NULL character.

     Following the header (or image directory if the montage
     keyword is in the header) is the binary image data itself.
     How the image data is formatted depends upon the class of
     the image as specified (or not specified) by the value of
     the class keyword in the header.

     DirectClass images (class=DirectClass) are continuous-tone,
     RGB images stored as intensity values in red-green-blue
     order.  Each color value is one byte in size [0..255] and
     there are three bytes per pixel (four with an optional matte
     value).  The total number of pixels in a DirectClass image
     is calculates by multiplying the rows value by the column
     value in the header.

     PseudoClass images (class=PseudoClass) are colormapped RGB
     images.  The colormap is stored as a series of red-green-
     blue pixel values, each value being a byte in size.  The
     number of colormap entries is indicated by the colors
     keyword in the header, with a maximum of 65,535 total
     entries allowed.  The colormap data occurs immediately
     following the header (or image directory if the montage
     keyword is in the header).

     PseudoClass image data is an array of index values into the
     color map.  If these are 256 or fewer colors in the image,
     each byte of image data contains an index value.  If the
     image contains more than 256 colors, then the index value is
     stored as two contiguous bytes with the most significant
     byte being first.  The total number of pixels in a
     PseudoClass image is calculated by multiplying the rows
     value by the columns value in the header.

     MIFF is capable of storing a digital signature for
     colormapped images.  This signature was developed for use
     when animating a sequence of images on a colormapped X
     server.  All of the signatures in a sequence of MIFF files
     are checked, and if they all match, you do not need to
     compute a global colormap.

     The default colormap identifier is a digital signature
     computed using RSA's Data Security MD5 Digest Algorithm.
     (See a description of this algorithm in Internet draft,
     [MD5], July 1992.  The colormap signature is computed if the
     MIFF file is part of a scene (i.e. the scene value does not
     equal 0).

     The image data in a MIFF file may be uncompressed or may be
     compressed using one of two algorithms.  The compression
     keyword in the header indicates how the image data is
     compressed. The run-length encoding (RLE) algorithm may be
     used to encode image data into packets of compressed data.
     For DirectClass images, runs of identical pixels values (not
     BYTE values) are encoded into a series of four-byte packets
     (five bytes if a matte value is included).  The first three
     bytes of the packet contain the red, green, and blue values
     of the pixel in the run.  The fourth byte contains the
     number of pixels in the run.  This value is in the range of
     0 to 255 and is one less than the actual number of pixels in
     the run.  For example, a value of 127 indicates that there
     are 128 pixels in the run.

     For PseudoClass images, the same RLE algorithm is used.
     Runs of identical index values are encoded into packets.
     Each packet contains the colormap index value followed by
     the number of index values in the run.  The number of bytes
     n a PseudoClass RLE packet will be either two or three,
     depending upon the size of the index values.  The number of
     RLE packets stored in the file is specified by the packets
     keyword in the header, but is not required.
     A more complex algorithm, the predictive arithmetic
     compression algorithm found in the lossless JPEG compression
     scheme, may be used to to achieve a greater compression
     ratio than run-length encoding.  PseudoClass images are
     first promoted to DirectClass before encoding.  The number
     of compressed packets stored in the file is specified by the
     packets keyword in the header.

     MIFF files may contain more than one image.  Simply
     concatenate each individual image (composed of a header and
     image data) into one file.


SEE ALSO

     display(1), animate(1), import(1), montage(1), mogrify(1),
     convert(1), more(1), compress(1)


COPYRIGHT

     Copyright 1995 E. I. du Pont de Nemours and Company

     Permission to use, copy, modify, distribute, and sell this
     software and its documentation for any purpose is hereby
     granted without fee, provided that the above copyright
     notice appear in all copies and that both that copyright
     notice and this permission notice appear in supporting
     documentation, and that the name of E. I. du Pont de Nemours
     and Company not be used in advertising or publicity
     pertaining to distribution of the software without specific,
     written prior permission.  E. I. du Pont de Nemours and
     Company makes no representations about the suitability of
     this software for any purpose.  It is provided "as is"
     without express or implied warranty.

     E. I. du Pont de Nemours and Company disclaims all
     warranties with regard TO this software, including all
     implied warranties of merchantability and fitness, in no
     event shall E. I. du Pont de Nemours and Company be liable
     for any special, indirect or consequential damages or any
     damages whatsoever resulting from loss of use, data or
     profits, whether in an action of contract, negligence or
     other tortuous action, arising out of or in connection with
     the use or performance of this software.


AUTHORS

     John Cristy, E.I. du Pont de Nemours and Company
     Incorporated







[home page]