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) , which does the 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) can generate a whole 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(5) , pnm(5) ,
HISTORY
This program was added to Netpbm in Release 10.3 (June 2002).