Pgmabel User Manual

pgmabel - create cross section using Abel Integration for Deconvolution

pgmabel [-help] [-axis axis] [-factor factor] [-pixsize pixsize] [-left | -right] [-verbose] [filespec]

This program is part of Netpbm(1).

pgmabel reads as input a PGM image, which it assumes to be an image of a rotational symmetric transparent object. The image must have a vertical symmetry axis. pgmabel produces as output an image of a cross-section of the image.

pgmabel does the calculation by performing the Abel Integration for Deconvolution of an axial-symmetrical image by solving the system of linear equations.

After integration, pgmabel weights all gray-values of one side by the surface area of the calculated ring in square pixels divided by 4*factor multiplied by the size of one pixel (pixsize). With the -verbose option, pgmabel prints the weighting factors.

Where the caculation generates a negative result, the output is black.

The computation is unstable against periodic structures with size 2 in the vertical direction.

You can abbreviate any option to its shortest unique prefix.

-help

Prints a help message.

-axis axis

Position of the axis of symmetry in the image in pixels from the left edge of the image. Default is the center of the image.

-factor factor

User defined factor for enhancement of the output. Use a factor less than 1 for decreasing gary values. Default is 1.0.

-pixsize pixsize

The size of a pixel for getting scale invariant. Default is 0.1.

-left

Calculate only the left side of the image. You cannot specify both left and right.

-right

Analogous to -left.

-verbose

print information about the calculation.

Rotate a PGM image to get an image with a vertical axis of symmetry, then calculate the cross section:

    pnmrotate 90 file.pgm | pgmabel -axis 140 >cross_section.pgm

pnmrotate(1), pgm(1),

This program was added to Netpbm in Release 10.3 (June 2002).

Volker Schmidt (lefti@voyager.boerde.de)

Copyright (C) 1997-2002 German Aerospace research establishment