HFANT

Section: User Commands (1)
Updated: November 11, 1985
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NAME

hfant - perform simple spatial transforms on a hips sequence of images  

SYNOPSIS

hfant [-s xscale yscale] [-v] [-a angle] [-o xoff yoff ] < infile > outfile  

DESCRIPTION

hfant 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. Fant uses a two-pass sampling technique to perform the transformation. hfant is for byte-formatted images, and hfant_sh is for short-formatted images.

The following options are available:

-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 below). If an image is only scaled in Y and no rotation is performed, hfant only uses one sampling pass over the image, cutting the computation time in half.

-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.

-o 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.

 

AUTHOR

John W. Peterson
Brian Tierney (LBL) converted for hips file format (9/89)  

BUGS

hfant was implemented with floating point arithmetic. It would undoubtedly run faster if integer arithmetic was used.

Negative rotations are implemented but don't quite work right.


 

Index

NAME
SYNOPSIS
DESCRIPTION
AUTHOR
BUGS

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