pamcomp, pnmcomp, pnmconvol, pnmcrop, pnmgamma: add pages (#12197)

* pamcomp, pnmcomp, pnmconvol, pnmcrop, pnmgamma: add pages

* Update pages/common/pnmgamma.md

Co-authored-by: K.B.Dharun Krishna <kbdharunkrishna@gmail.com>

---------

Co-authored-by: K.B.Dharun Krishna <kbdharunkrishna@gmail.com>

pages/common/pnmgamma.md

@@ -0,0 +1,20 @@
+# pnmgamma
+
+> Perform gamma correction on PNM images.
+> More information: <https://netpbm.sourceforge.net/doc/pnmgamma.html>.
+
+- Convert the image from BT.709 luminance to radiance or sRGB luminance:
+
+`pnmgamma -{{bt709tolinear|bt709tosrgb}} {{path/to/image.pnm}} > {{path/to/output.pnm}}`
+
+- Convert the image from radiance or sRGB luminance to BT.709 luminance:
+
+`pnmgamma -{{lineartobt709|srgbtobt709}} {{path/to/image.pnm}} > {{path/to/output.pnm}}`
+
+- Specify the gamma value used for the gamma transfer function:
+
+`pnmgamma -gamma {{value}} {{path/to/image.pnm}} > {{path/to/output.pnm}}`
+
+- Specify the gamma value used for the gamma transfer function per color component:
+
+`pnmgamma -rgamma {{value}} -ggamma {{value}} -bgamma {{value}} {{path/to/image.pnm}} > {{path/to/output.pnm}}`