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pamflip

NAME

pamflip - flip or rotate a PAM or PNM image

SYNOPSIS

pamflip { -leftright | -lr | -topbottom | -tb | -transpose | -xy | -rotate90 | -r90 | -cw | -rotate270 | -r270 | -ccw | -rotate180 | -r180 -null | -xform=xform1,xform2... } [-memsize=mebibytes] [-pagesize=bytes] [pamfile]

All options can be abbreviated to their shortest unique prefix. You may use two hyphens instead of one to designate an option. You may use either white space or an equals sign between an option name and its value.

DESCRIPTION

This program is part of Netpbm(1).

pamflip flips a PAM or PNM image top for bottom or left for right, or transposes it horizontal for vertical, or rotates it 1, 2, or 3 quarter turns.

To rotate at other angles, use pnmrotate. It is much slower, though.

The input image is pamfile, or Standard Input if pamfile is not specified.

To flip/rotate a JFIF (JPEG) image losslessly, use jpegtran. jpegtran is part of the Independent Jpeg Group's compression library package, not part of Netpbm. The normal Netpbm way to flip a JFIF file would be to convert it to PNM, use pamflip, and convert back to JFIF. But since JPEG compression is lossy, the resulting image would have less quality than the original. jpegtran, on the other hand, can do this particular transformation directly on the compressed data without loss.

OPTIONS

You must supply exactly one of the following options:

pamflip's predecessor (before Netpbm 10.7 - August 2002) pnmflip did not have the -xform option and instead allowed you to specify any number of the other options, including zero. It applied all the indicated transformations, in the order given, just like with pamflip's -xform option. (Reason for the change: this kind of interpretation of options is inconsistent with the rest of Netpbm and most of the Unix world, and thus hard to understand and to implement).

-leftright

-lr

Flip left for right.

-topbottom

-tb

Flip top for bottom.

-transpose

-xy

Transpose horizontal for vertical. I.e. make the pixel at (x,y) be at (y,x).

-rotate90

-r90

-ccw

Rotate counterclockwise 90 degrees.

-rotate180

-r180

Rotate 180 degrees.

-rotate270

-r270

-cw

Rotate counterclockwise 270 degrees (clockwise 90 degrees)

-null

No change. (The purpose of this option is the convenience of programs that invoke pamflip after computing the kind of transformation desired, including none at all).

This option was new in Netpbm 10.13 (December 2002).
     

-xform=xform1,xform2...

Apply all the transforms listed, in order. The valid values for the transforms are as follows and have the same meanings as the identically named options above.

*

leftright

*

topbottom

*

transpose

This option was new in Netpbm 10.13 (December 2002).

The following options help pamflip use memory efficiently. Some flipping operations on very large images can cause pamflip to have a very large working set, which means if you don't have enough real memory, the program can page thrash, which means it takes a ridiculous amount time to run. If your entire image fits in real memory, you don't have a problem. If you're just flipping top for bottom or left for right, you don't have a problem. Otherwise, pay attention. If you're interested in the details of the thrashing problem and how pamflip approaches it, you're invited to read a complete explanation in comments in the source code.

-memsize=mebibytes

mebibytes is the size in mebibytes (aka megabytes) of real memory (not virtual) available for pamflip. pamflip does nothing special to allocate real memory or control it's allocation -- it gets whatever it gets just by referencing virtual memory normally. This is the maximum amount that pamflip can be expected to end up with by doing that. This is just about impossible for you to know, of course, but you can estimate. The total real memory in your system should be a major factor in your estimate.

When you specify -memsize and are doing a row for column type of transformation, pamflip does the transformation in multiple passes, each one with a working set size less than the specified value.

If your estimate is even slightly too large, it's the same as infinity. If you estimate too small, pamflip will use more passes than it needs to, and thus will slow down proportional to the underestimate.

If you do not specify -memsize, pamflip assumes infinite real memory and does the entire transformation in one pass.

This option did not exist before Netpbm 10.7 (August 2002).
     

-pagesize=bytes

bytes is the size in bytes of a paging unit -- the amount of memory that gets paged in or out as an indivisible unit -- in your system. The default is 4KiB.

This option did not exist before Netpbm 10.7 (August 2002).

Miscellaneous options:

-verbose

This option causes pamflip to issue messages to Standard Error about its progress.

SEE ALSO

pnmrotate(1), pnm(1), jpegtran manual

HISTORY

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

AUTHOR

Copyright (C) 1989 by Jef Poskanzer.