pamfunc, ppmchange, ppmcie, ppmcolormask, ppmdim, ppmdist, ppmfade, ppmforge: add pages (#11449)

Co-authored-by: Lena <126529524+acuteenvy@users.noreply.github.com>

pages/common/pamfunc.md

@@ -0,0 +1,12 @@
+# pamfunc
+
+> Apply a simple arithmetic function to a Netpbm image.
+> More information: <https://netpbm.sourceforge.net/doc/pamfunc.html>.
+
+- Apply the specified arithmetic function with `n` as the second argument to each sample in the specified PAM image:
+
+`pamfunc -{{multiplier|divisor|adder|subtractor|min|max}} {{n}} {{path/to/input.pam}} > {{path/to/output.pam}}`
+
+- Apply the specified bit string function with `n` as the second argument to each sample in the specified PAM image:
+
+`pamfunc -{{andmask|ormask|xormask|shiftleft|shiftright}} {{n}} {{path/to/input.pam}} > {{path/to/output.pam}}`