1Pamflip User Manual(0)                                  Pamflip User Manual(0)
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NAME

6       pamflip - flip or rotate a PAM or PNM image
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SYNOPSIS

10       pamflip  {  -leftright  |  -lr  | -topbottom | -tb | -transpose | -xy |
11       -rotate90 | -r90 | -cw | -rotate270 | -r270 | -ccw | -rotate180 | -r180
12       -null   |   -xform=xform1,xform2...    }  [-memsize=mebibytes]  [-page‐
13       size=bytes] [pamfile]
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15       All options can be abbreviated to their shortest  unique  prefix.   You
16       may use two hyphens instead of one to designate an option.  You may use
17       either white space or an equals sign between an  option  name  and  its
18       value.
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DESCRIPTION

23       This program is part of Netpbm(1).
24
25       pamflip  flips  a PAM or PNM image top for bottom or left for right, or
26       transposes it horizontal for vertical, or rotates it 1, 2, or 3 quarter
27       turns.
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29       To rotate at other angles, use pnmrotate.  It is much slower, though.
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31       The  input image is pamfile, or Standard Input if pamfile is not speci‐
32       fied.
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34       To flip/rotate a JFIF (JPEG) image losslessly, use jpegtran.   jpegtran
35       is  part  of  the Independent Jpeg Group's compression library package,
36       not part of Netpbm.  The normal Netpbm way to flip a JFIF file would be
37       to convert it to PNM, use pamflip, and convert back to JFIF.  But since
38       JPEG compression is lossy, the resulting image would have less  quality
39       than the original.  jpegtran, on the other hand, can do this particular
40       transformation directly on the compressed data without loss.
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OPTIONS

45       You must supply exactly one of the following options:
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47       pamflip's predecessor (before Netpbm 10.7 - August  2002)  pnmflip  did
48       not  have the -xform option and instead allowed you to specify any num‐
49       ber of the other options, including zero.  It applied all the indicated
50       transformations,  in  the  order given, just like with pamflip's -xform
51       option.  (Reason for the change: this kind of interpretation of options
52       is inconsistent with the rest of Netpbm and most of the Unix world, and
53       thus hard to understand and to implement).
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57       -leftright
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59       -lr    Flip left for right.
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62       -topbottom
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64       -tb    Flip top for bottom.
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67       -transpose
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69       -xy    Transpose horizontal for vertical.  I.e. make the pixel at (x,y)
70              be at (y,x).
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73       -rotate90
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75       -r90
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77       -ccw   Rotate counterclockwise 90 degrees.
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80       -rotate180
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82       -r180  Rotate 180 degrees.
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85       -rotate270
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87       -r270
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89       -cw    Rotate counterclockwise 270 degrees (clockwise 90 degrees)
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92       -null  No  change.   (The  purpose of this option is the convenience of
93              programs that invoke pamflip after computing the kind of  trans‐
94              formation desired, including none at all).
95
96              This option was new in Netpbm 10.13 (December 2002).
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99       -xform=xform1,xform2...
100              Apply all the transforms listed, in order.  The valid values for
101              the transforms are as follows and have the same meanings as  the
102              identically named options above.
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104
105       ·      leftright
106
107       ·      topbottom
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109       ·      transpose
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111
112              This option was new in Netpbm 10.13 (December 2002).
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116       The  following options help pamflip use memory efficiently.  Some flip‐
117       ping operations on very large images can cause pamflip to have  a  very
118       large  working  set,  which means if you don't have enough real memory,
119       the program can page thrash, which means it takes a  ridiculous  amount
120       time  to run.  If your entire image fits in real memory, you don't have
121       a problem.  If you're just flipping top for bottom or left  for  right,
122       you  don't have a problem.  Otherwise, pay attention.  If you're inter‐
123       ested  in  the  details  of  the  thrashing  problem  and  how  pamflip
124       approaches  it,  you're  invited to read a complete explanation in com‐
125       ments in the source code.
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129       -memsize=mebibytes
130              mebibytes is the size in mebibytes  (aka  megabytes)  of  memory
131              available  for  pamflip.  It is the lesser of the amount of real
132              or virtual memory available.
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134              pamflip does nothing special to allocate real memory or  control
135              it's  allocation -- it gets whatever it gets just by referencing
136              virtual memory normally.  The real memory figure in question  is
137              the  maximum  amount that pamflip can be expected to end up with
138              by doing that.  This is just about impossible for you  to  know,
139              of  course, but you can estimate.  The total real memory in your
140              system should be a major factor in your estimate.
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142              If pamflip cannot fit the entire image in the amount  of  memory
143              you  specify, it does the transformation in chunks, using tempo‐
144              rary files for intermediate results.
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146              Strict horizontal transformations  (either  left  for  right  or
147              null),  pamflip  never keeps more than one row in memory, so the
148              memory size is irrelevant  and  pamflip  doesn't  use  temporary
149              files.
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151              The  real  memory is important when you do a column for row type
152              of transformation (e.g. -rotate90).  In that case, even if  pam‐
153              flip  can  fit the entire image in virtual memory at once, if it
154              does not also fit in real memory, the program will  thrash  like
155              crazy because of the order in which pamflip accesses the pixels,
156              and that means it will take a ridiculously long time to run.   A
157              proper -memsize drastically reduces the paging.
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159              If  you  specify  -memsize too large, pamflip may attempt to get
160              more virtual memory than the system allows it and fail.   If  it
161              can  get  the  virtual  memory,  but -memsize is larger than the
162              amount of real memory the system allows it and  the  transforma‐
163              tion is row for column, it will page thrash and run very slowly.
164              A value even slightly too high is the same as infinity.
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166              If you specify -memsize too small, the program will run slightly
167              more  slowly  due  to  extra  overhead in manipulating temporary
168              files.  Also, if your environment isn't set up to make temporary
169              files possible, pamflip will fail.
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171              Doing the entire transformation 'in memory' doesn't speed things
172              up as much as you might think, because even with  the  temporary
173              files, the data is just as likely to be in memory.  Virtual mem‐
174              ory gets paged to disk and disk files get cached in memory.   In
175              fact, the pixels fit much more compactly into memory when stored
176              in a temporary file than when stored 'in memory' because pamflip
177              uses  a  more  efficient  format.  So you're likely to have less
178              disk I/O when you allow pamflip less memory.
179
180              If you do not specify -memsize, pamflip assumes infinity.
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182              This option did not exist before Netpbm 10.7 (August 2002).
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184              Before Netpbm 10.42 (March 2008), this option  applied  only  to
185              real memory.  pamflip would always keep the entire image in vir‐
186              tual memory and if it could not get enough  virtual  memory,  it
187              failed.   pamflip  accessed  the  pixels in an order designed to
188              keep real memory use within the specified amount.
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190
191       -pagesize=bytes
192              bytes is the size in bytes of a paging unit  --  the  amount  of
193              memory  that  gets  paged in or out as an indivisible unit -- in
194              your system.  The default is 4KiB.
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196              This option has no effect.
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198              Before Netpbm 10.42 (March 2008), pamflip used it to control its
199              use of real memory.
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201              This option did not exist before Netpbm 10.7 (August 2002).
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204
205              Miscellaneous options:
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208       -verbose
209              This  option  causes pamflip to issue messages to Standard Error
210              about its progress.
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SEE ALSO

216       pnmrotate(1), pnm(1), pam(1), jpegtran manual
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HISTORY

220       pamflip replaced pnmflip in Netpbm 10.13 (December 2002).   pamflip  is
221       backward compatible, but also works on PAM images.
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AUTHOR

226       Copyright (C) 1989 by Jef Poskanzer.
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230netpbm documentation            20 January 2008         Pamflip User Manual(0)
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