Pamenlarge User Manual(0) Pamenlarge User Manual(0)NAMEpamenlarge - Enlarge a Netpbm image N times
SYNOPSISpamenlarge N [pnmfile]
DESCRIPTION
This program is part of Netpbm(1)pamenlarge reads a Netpbm image as input, replicates its pixels N
times, and produces a Netpbm image as output. The output is the same
type of image as the input.
If you enlarge by a factor of 3 or more, you should probably add a
pnmsmooth step; otherwise, you can see the original pixels in the
resulting image.
For PBM images, pamenlarge uses special fast algorithms for scale fac‐
tors up to 10. For larger factors, it uses a simple but slow algo‐
rithm. As a result, you can often get a significantly faster scale by
running pamenlarge multiple times. For example, enlarging by 3 and
then by 5 is faster than enlarging once by 15. And because the algo‐
rithms are different for the different scale factors, some faster than
others, the order matters too. For example, the following examples all
produce the same output -- an image 15 times bigger on edge than the
input -- but with at different spees, each being faster than the one
before.
$ pamenlarge 15 test.pbm
$ pamenlarge 5 test.pbm | pamenlarge 3
$ pamenlarge 3 test.pbm | pamenlarge 5
The special fast cases for factors up to 10 have existed since Release
10.50 (March 2010). The special cases for 1, 2, 3, and 5 go back to
Release 10.41 (December 2007). Before 10.41, there are no special
scale factors and PBM enlargement is significantly slower than today
for all scale factors.
pamenlarge can enlarge only by integer factors. The slower but more
general pamscale can enlarge or reduce by arbitrary factors. pamscale
allows you to enlarge by resampling, which gives you smoother enlarge‐
ments. But it is much slower.
pamstretch is another enlarging program that enlarges by integer fac‐
tors. It does a simple kind of resampling that gives you a smoothed
enlargement with less computational cost.
pbmreduce can reduce by integer factors, but only for PBM images.
HISTORYpamenlarge was new in Netpbm 10.25 (October 2004). It is designed as a
replacement for pnmenlarge by Jef Poskanzer, which was in Pbmplus as
far back as 1989. The major difference is that pamenlarge can enlarge
PAM format images in addition to PNM.
SEE ALSOpbmreduce(1) , pamscale(1) , pamstretch(1) , pbmpscale(1) ,
pnmsmooth(1) , pnm(1)AUTHOR
Copyright (C) 1989 by Jef Poskanzer.
netpbm documentation 17 March 2010 Pamenlarge User Manual(0)
