Magick Image File Format (MIFF) 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.).
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 data by a :
character immediately followed by a newline.
The MIFF header is composed entirely of LATIN-1 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
- the type of binary image data stored in the MIFF file. If this
keyword is not present, DirectClass image data is assumed.
- colors=value
- 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
- the width of the image in pixels. This is a
required keyword and has no default.
- compression=RunlengthEncoded
- compression=Zip
- the type of algorithm
used to compress the image data. If this keyword is
not present, the image data is assumed to be
uncompressed.
- delay <1/100ths of a second>
- the interframe delay in an image sequence. The maximum delay is 65535.
- depth=8
- depth=16
- depth of a single color value representing values from 0 to
255 (depth 8) or 65535 (depth 16). If this keyword is absent, a depth of 8 is
assumed.
- gamma=value
-
gamma of the image. If it is not specified, a gamma of 1.0
(linear brightness response) is assumed,
- id=ImageMagick
- identify 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.
- label="value"
- this optional keyword defines a short title or caption for the image. If
any whitespace appears in the label, it must be enclosed within double
quotes.
- 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 pseudocolor 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
- the number of compressed color packets in the
image data section. This keyword is optional for
RunlengthEncoded images, mandatory for
Zip compressed images,
and not used for uncompressed image.
- rows=value
- the height of the image in pixels. This is a
required keyword and has no default.
- scene=value
- 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 pixel contents. RSA's Data Security MD5 Digest Algorithm is
recommended.
The following is a sample MIFF header. In this example,
<FF> is a formfeed character:
id=ImageMagick
class=PseudoClass colors=256
compression=RunlengthEncoded packets=27601
columns=1280 rows=1024
scene=1
signature=d79e1c308aa5bbcdeea8ed63df412da9
{
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 for an image depth of 8 and there
are three bytes per pixel (four with an optional matte value). If the depth
is 16, each color value is two bytes with the most significant byte being first.
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. If the image depth is 16,
each colormap entry is two bytes with the most significant byte being
first. 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 or the depth is 16, 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.
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.
Use Zip compression
to achieve a greater compression ratio than run-length 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.
Copyright
Copyright 1998 E. I. du Pont de Nemours and Company
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files ("ImageMagick"),
to deal in ImageMagick without restriction, including without limitation
the rights to use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of ImageMagick, and to permit persons to whom the
ImageMagick is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of ImageMagick.
The software is provided "as is", without warranty of any kind, express or
implied, including but not limited to the warranties of merchantability,
fitness for a particular purpose and noninfringement.In no event shall
E. I. du Pont de Nemours and Company be liable for any claim, damages or
other liability, whether in an action of contract, tort or otherwise,
arising from, out of or in connection with ImageMagick or the use or other
dealings in ImageMagick.
Except as contained in this notice, the name of the E. I. du Pont de
Nemours and Company shall not be used in advertising or otherwise to
promote the sale, use or other dealings in ImageMagick without prior
written authorization from the E. I. du Pont de Nemours and Company.
Authors
John Cristy,
cristy@mystic.es.dupont.com, E.I. du Pont de Nemours and Company
Incorporated.
Image manipulation software that works like magic.