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Man Pages


Manual Reference Pages  -  FANT (1)

NAME

fant - perform simple spatial transforms on an image

CONTENTS

Synopsis
Description
Options
See Also
Authors
Bugs

SYNOPSIS

fant [ -a angle ] [ -b blurfactor ] [ -o outfile ] [ -p xoff yoff ] [ -s xscale yscale ] [ -S xsize ysize ] [ -v ] [ infile ]

DESCRIPTION

Fant rotates or scales an image by an arbitrary amount. It does this by using pixel integration (if the image size is reduced) or pixel interpolation if the image size is increased. Because it works with subpixel precision, aliasing artifacts are not introduced (hah! see BUGS). Fant uses a two-pass sampling technique to perform the transformation. If infile is "-" or absent, input is read from the standard input.

OPTIONS

-a angle
  Amount to rotate image by, a real number from 0 to 45 degrees (positive numbers rotate clockwise). Use rleflip(1) first to rotate an image by larger amounts.
-b blur_factor
  Control the amount of blurring in the output image. If the blur factor is greater than one, image blurring will increase. If the blur factor is smaller than one, image blurring will decrease but aliasing artifacts may be visible.

-o outfile
  Specifies where to place the resulting image. The default is to write to stdout. If outfile is "-", the output will be written to the standard output stream.
-p xoff yoff
  Specifies where the origin of the image is - the image is rotated or scaled about this point. If no origin is specified, the center of the image is used.
-s xscale yscale
  The amount (in real numbers) to scale an image by. This is often useful for correcting the aspect of an image for display on a frame buffer with non square pixels. For this use, the origin should be specified as 0, 0 (see -p above). If an image is only scaled in Y and no rotation is performed, fant only uses one sampling pass over the image, cutting the computation time in half.
-S xsize ysize
  An alternate method of specifying the scale factors. xsize and ysize give the desired output image size.

The -S option can not be used in combination with -a, -p, or -s.

-v Verbose output. Primarily for debugging.

SEE ALSO

avg4(1), rleflip(1), rlezoom(1), urt(1), RLE(5),
Fant, Karl M. "A Nonaliasing, Real-Time, Spatial Transform Technique", IEEE CG&A, January, 1986, p. 71.

AUTHORS

John W. Peterson, James S. Painter

BUGS

Fant uses a rather poor anti-aliasing filter (a triangle filter). This is usually good enough but will exhibit noticeable aliasing artifacts on nasty input images.
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--> FANT (1) Dec 4, 1990

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