NAME¶

pamfunc - Apply a simple monadic arithmetic function to a Netpbm image

SYNOPSIS¶

pamfunc { -multiplier=realnum | -divisor=realnum | -adder=integer | -subtractor=integer | -min=wholenum | -max=wholenum -andmask=hexmask -ormask=hexmask -xormask=hexmask -not -shiftleft=count -shiftright=count } [filespec]

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

DESCRIPTION¶

This program is part of Netpbm(1).

pamfunc reads a Netpbm image as input and produces a Netpbm image as output, with the same format, maxval, and dimensions as the input. pamfunc applies a simple transfer function to each sample in the input to generate the corresponding sample in the output. The options determine what function.

pamarith is the same thing for binary functions -- it takes two images as input and applies a specified simple arithmetic function (e.g. addition) on pairs of samples from the two to produce the single output image.

OPTIONS¶

-multiplier=realnum

This option makes the transfer function that of multiplying by
realnum. realnum must be nonnegative. If the result
is greater than the image maxval, it is clipped to the maxval.

Where the input is a PGM or PPM image, this has the effect of
dimming or brightening it. For a different kind of brightening,
see ppmbrighten(1)and ppmflash(1)

Also, see ppmdim(1),whichdoesthe
same thing as pamfunc -multiplier on a PPM image with a
multiplier between 0 and 1,
except it uses integer arithmetic, so it may be faster.

And ppmfade(1)cangenerateawhole
sequence of images of brightness declining to black or increasing to
white, if that's what you want.

-divisor=realnum

This option makes the transfer function that of dividing by
realnum. realnum must be nonnegative. If the result
is greater than the image maxval, it is clipped to the maxval.

This is the same function as you would get with -multiplier,
specifying the multiplicative inverse of realnum.

-adder=integer

This option makes the transfer function that of adding
wholenum. If the result is greater than the image maxval,
it is clipped to the maxval. If it is less than zero, it is
clipped to zero.

Note that in mathematics, this entity is called an 'addend,'
and an 'adder' is a snake. We use 'adder' because
it makes more sense.

-subtractor=integer

This option makes the transfer function that of subtracting
wholenum. If the result is greater than the image maxval,
it is clipped to the maxval. If it is less than zero, it is
clipped to zero.

Note that in mathematics, this entity is called a
'subtrahend' rather than a 'subtractor.' We
use 'subtractor' because it makes more sense.

This is the same function as you would get with -adder,
specifying the negative of integer.

-min=wholenum

This option makes the transfer function that of taking the
maximum of the argument and wholenum. I.e the minimum
value in the output will be wholenum.

If wholenum is greater than the maxval, though, every sample
in the output will be maxval.

-max=wholenum

This option makes the transfer function that of taking the
minimum of the argument and wholenum. I.e the maximum
value in the output will be wholenum.

If wholenum is greater than the maxval, the function is
idempotent -- the output is identical to the input.

-andmask=hexmask

This option makes the transfer function that of bitwise anding
with hexmask.

hexmask is in hexadecimal. Example: 0f

See section Maxval for the special
meaning of maxval with respect to bit string operations such as
this.

This option was new in Netpbm 10.40 (September 2007).

-ormask=hexmask

This option makes the transfer function that of bitwise
inclusive oring with hexmask.

This is analogous to -andmask.

This option was new in Netpbm 10.40 (September 2007).

-xormask=hexmask

This option makes the transfer function that of bitwise
exclusive oring with hexmask.

This is analogous to -andmask.

This option was new in Netpbm 10.40 (September 2007).

-not

This option makes the transfer function that of bitwise logical
inversion (e.g. sample value 0xAA becomes 0x55).

See section Maxval for the special
meaning of maxval with respect to bit string operations such as
this.

pnminvert does the same thing for a bilevel visual image
which has maxval 1 or is of PBM type.

This option was new in Netpbm 10.40 (September 2007).

-shiftleft=count

This option makes the transfer function that of bitwise shifting
left by count bits.

See section Maxval for the special
meaning of maxval with respect to bit string operations such as
this.

This option was new in Netpbm 10.40 (September 2007).

-shiftright=count

This option makes the transfer function that of bitwise shifting
right by count bits.

This is analogous to -shiftleft.

This option was new in Netpbm 10.40 (September 2007).

MAXVAL¶

For the arithmetic functions, the maxval has no meaning. The function applies to the sample value as an integer. (Note that this differs from the usual interpretation of PAM samples as being a fraction of a maxval, but does produce more intuitive result: 2 times 5 is 10.

But with the bit string operations, the maxval has a special meaning. The functions in question are: -andmask, -ormask, -xormask, -not, -shiftleft, and -shiftright.

With these, each sample value the input image, and in the output image, represents a bit string, not a number. The maxval tells how wide the bit string is. The maxval must be a full binary count (a power of two minus one, such as 0xff) and the number of ones in it is the width of the bit string.

For a masking function, the mask value you specify must not have more significant bits than the width indicated by the maxval.

For a shifting operation, the shift count you specify must not be greater than the width indicated by the maxval.

The maxval of the output image is the same as that of the input image.

SEE ALSO¶

ppmdim(1), ppmbrighten(1), pamdepth(1), pamarith(1), pamsummcol(1), pamsumm(1), ppmfade(1), pnminvert(1), pam(1), pnm(1),

HISTORY¶

This program was added to Netpbm in Release 10.3 (June 2002).