pamfixtrunc, pamfix, pamvalidate: add pages (#12406)

* pamfixtrunc, pamfix, pamvalidate: add pages

---------

Co-authored-by: Vitor Henrique <87824454+vitorhcl@users.noreply.github.com>
Co-authored-by: K.B.Dharun Krishna <kbdharunkrishna@gmail.com>

pages/common/pamfix.md

@@ -0,0 +1,17 @@
+# pamfix
+
+> Fix errors in PAM, PBM, PGM and PPM files.
+> See also: `pamfile`, `pamvalidate`.
+> More information: <https://netpbm.sourceforge.net/doc/pamfix.html>.
+
+- Fix a Netpbm file that is missing its last part:
+
+`pamfix -truncate {{path/to/corrupted.ext} > {{path/to/output.ext}}`
+
+- Fix a Netpbm file where pixel values exceed the image's `maxval` by lowering the offending pixels' values:
+
+`pamfix -clip {{path/to/corrupted.ext}} > {{path/to/output.ext}}`
+
+- Fix a Netpbm file where pixel values exceed the image's maxval by increasing it:
+
+`pamfix -changemaxval {{path/to/corrupted.pam|pbm|pgm|ppm}} > {{path/to/output.pam|pbm|pgm|ppm}}`

pages/common/pamfixtrunc.md

@@ -0,0 +1,8 @@
+# pamfixtrunc
+
+> This command is superseded by `pamfix -truncate`.
+> More information: <https://netpbm.sourceforge.net/doc/pamfixtrunc.html>.
+
+- View documentation for the current command:
+
+`tldr pamfix`

pages/common/pamvalidate.md

@@ -0,0 +1,9 @@
+# pamvalidate
+
+> Validate PAM, PGM, PBM and PPM files.
+> See also: `pamfile`, `pamfix`.
+> More information: <https://netpbm.sourceforge.net/doc/pamvalidate.html>.
+
+- Copy a Netpbm file from `stdin` to `stdout` if and only if it valid; fail otherwise:
+
+`{{command}} | pamvalidate > {{path/to/output.ext}}`