Update cheatsheets

hipstopgm

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+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# hipstopgm
+
+> Read a HIPS file as input and return a PGM image as output.
+> If the HIPS file contains more than one frame in sequence, `hipstopgm` will concatenate all the frames vertically.
+> More information: <https://netpbm.sourceforge.net/doc/hipstopgm.html>.
+
+- Convert a HIPS file into a PGM image:
+
+`hipstopgm {{path/to/file.hips}}`
+
+- Suppress all informational messages:
+
+`hipstopgm -quiet`
+
+- Display version:
+
+`hipstopgm -version`