Update cheatsheets

ppmtospu

@@ -0,0 +1,17 @@
+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# ppmtospu
+
+> Convert a PPM file to an Atari Spectrum 512 image.
+> More information: <https://netpbm.sourceforge.net/doc/ppmtospu.html>.
+
+- Convert a PPM file to an Atari Spectrum 512 image:
+
+`ppmtospu {{path/to/input.ppm}} > {{path/to/output.spu}}`
+
+- Use a dithering matrix of the specified size (0 means no dithering):
+
+`ppmtospu -d{{0|2|4}} {{path/to/input.ppm}} > {{path/to/output.spu}}`