resample(9) [plan9 man page]

RESAMPLE(9.1)															     RESAMPLE(9.1)

NAME

       resample, pdup - resample a picture

SYNOPSIS

       fb/resample width [ input ] [ B C ]

       fb/pdup sx sy [ input ]

DESCRIPTION

       Resample  resamples  the scan lines of its input image (default standard input) to the given new width.	The image is decimated or interpo-
       lated using a well-designed cubic filter.  See transpose(9.1) for assistance with vertical resampling.

       The reference explains the optional filter parameters B and C.  The default values give optimal alias rejection, and should not normally be
       tampered with.

       Pdup  scales  an image by pixel duplication.  Sx and sy are the horizontal and vertical scale factors.  They must be positive integers.	In
       the output image (written on standard output), each pixel of the input image (default standard input) generates an sxxsy block of identical
       pixels.

SOURCE

       /sys/src/fb/resample.c
       /sys/src/fb/pdup.c

SEE ALSO

       picfile(9.6), Don P. Mitchell and Arun Netravali, ``Reconstruction in Computer Graphics'', SIGGRAPH '88 Conference Proceedings.

																     RESAMPLE(9.1)

TRANSPOSE(9.1)															    TRANSPOSE(9.1)

NAME

       rotate, transpose - re-orient an image

SYNOPSIS

       fb/rotate angle [ input ]

       fb/transpose [ -vhadrlui ] [ -ox y ] [ input ]

DESCRIPTION

       Rotate  rotates the image in its input picture file (default standard input) clockwise by angle degrees, writing the resulting picture file
       on standard output.

       Transpose turns its input picture file on its side by reflection through its major (descending from left to right)  diagonal,  writing  the
       resulting  picture file on standard output.  If no file name is given, the picture is read from standard input.	Options yield all possible
       symmetries of the square grid:

       -d     reflects the image through its descending diagonal (the default).

       -a     reflects the image through its ascending diagonal.

       -v     reflects the image left-to-right through its vertical center line.

       -h     inverts the image top-to-bottom through its horizontal center line.

       -r     rotates the image to the right (clockwise) 90 degrees.

       -l     rotates the image to the left (counterclockwise) 90 degrees.

       -u     rotates the image upside down (180 degrees).

       -i     identity transformation (for completeness only.)

       -o x y translates by (x,y).  Without -o, the input and output files have the same upper-left corner.

       Transpose is particularly useful to convince programs that work on the rows of a picture file to operate on columns.  For example

	      fb/transpose big |
		   fb/resample 48 |
		   fb/transpose |
		   fb/resample 48 >tiny

       makes a tiny 48x48 version of a big picture.

SOURCE

       /sys/src/fb/rotate.c
       /sys/src/fb/transpose.c

SEE ALSO

       picfile(9.6), resample(9.1)

BUGS

       Very large images may not fit in memory.  The result of rotate is not anti-aliased.

																    TRANSPOSE(9.1)