Update cheatsheets

pnmhistmap

@@ -0,0 +1,21 @@
+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# pnmhistmap
+
+> Draw a histogram of a PNM image.
+> More information: <https://netpbm.sourceforge.net/doc/pnmhistmap.html>.
+
+- Draw a histogram of a PNM image:
+
+`pnmhistmap {{path/to/input.pnm}} > {{path/to/output.pnm}}`
+
+- Draw the histogram as dots instead of bars:
+
+`pnmhistmap -dots {{path/to/input.pnm}} > {{path/to/output.pnm}}`
+
+- Specify the range of intensity values to include:
+
+`pnmhistmap -lval {{minval}} -rval {{maxval}} {{path/to/input.pnm}} > {{path/to/output.pnm}}`