iPOX

iPOX was an image processing system initiated at the Department of Earth Sciences, University of Oxford in the early 1990s, primarily to restore and enhance GLORIA data. (GLORIA is a side-scan sonar system that produces images of the seafloor.) iPOX, however, was not limited to the processing of GLORIA data. iPOX was conceived as a state of the art, general purpose system for the processing of single band imagery, and which could be extended to embrace the special needs of sidescan sonar data processing.

iPOX design features included:

• Modular design, each independent module performing a single limited task.
• Modules to read and write image data in other file formats, including WHIPS, GMT grd, USGS-mips, PGM, PBM, AVS field and PostScript.
• Ability to handle images in any of six data types; 8-bit byte, 16-bit short integer, 32-bit integer, float, double, and complex.
• Incorporation of the object-oriented programming techniques of data abstraction and polymorphism. These enable common ANSI C code to be used for all of the six image data types.
• Portable between UNIX systems; modules coded in ANSI C.
• External data representation (XDR) used to transfer images between computers with different architectures. XDR also is an extremely useful data representation for images that are to be archived.
• Algorithms configured to use a "line in, line out" paradigm. This minimises memory usage and so enables large images to be processed.
• Modules driven via command line options.
• Each module reads an image from standard input and writes to standard output. This allows modules to be "pipelined" and eliminates the need to store intermediate images on disk.
• Modules can be driven from a shell script (command procedure).
• X Windows pipeline editor tool (never implemented) can create and execute this shell script interactively.
• X Windows image viewer tool (never implemented) can view the image exiting from the pipeline.
• Binary image data prefaced by an ASCII text header consisting of key-value pairs. This allows the image header to be viewed using standard text reading utilities such as more.

iPOX contained 36 modules and consisted of over 14,000 lines of ANSI C code.

iPOX Modules

deshade

Deshade a sidescan sonar image.

bell

Remove/apply bell (MU) transform from a sidescan sonar image.

iread

Read an image in another file format (WHIPS, GMT grd, USGS-mips, AVS field, PGM ASCII, PGM raw, PBM ASCII, PBM raw or iPOX).

iwrite

Write an image in another file format (WHIPS, GMT grd, USGS-mips, AVS field, PGM ASCII, PGM raw, iPOX or raw).

itostat

Calculate image statistics.

itotext

Convert image values to text (suitable for inputting into xmgr/xvgr).

itops

Convert an image to PostScript.

pstopbm

Convert PostScript to a PBM raw image (uses Ghostscript).

pbmtovp

Plot a PBM raw image onto a Versatec electrostatic plotter.

chtype

Change image data type ("byte", "short", "int", "float", "double" or "complex").

chrep

Change image data representation ("native" or "xdr").

addhist

Add a History record to an image header.

zaphist

Trim the History in an image header.

smooth

Smooth an image.

median

Median filter an image.

convol

Apply a convolution filter to an image.

cross

Cross-correlate an image with a template image.

laplac

Laplacian filter an image (small filters have unbalanced weights).

mklap3

Make an image file containing a 3 by 3 Laplacian filter kernel.

sample

Reduce the size of an image by sampling.

average

Reduce the size of an image by averaging.

mag

Magnify the size of an image.

sub

Extract a sub-image from an image.

rotate

Rotate an image.

xflip

Flip an image horizontally.

dft

Fourier transform an image (uses a mixed radix FFT).

ctod

Convert complex image to double.

pogram

Calculate line periodograms for an image.

imath

Perform arithmetic on a pair of images.

abut

Abut two images.

scale

Scale the intensity values in an image.

clip

Clip the intensity values in an image.

xzap

Linear interpolate over column dropouts.

yzap

Linear interpolate over line dropouts.

mkflat

Make an image containing a constant pixel value.

meter

Meter the progress of the processing pipeline.