Uses ImageMagic to generatee an image of a starry night and save it as starry_night.jpg.

Makefile

#!/usr/bin/env make
# This file contains TAB characters, in addition to spaces.

MAGIC:=convert
OUTPUT:=starry_night.jpg
SIZE:=1920x1080
HOW_STARRY:=10
HOW_BLURRY:=0x2
COW:="40%,50%"

.PHONY: starry_night levels blur noise black magic

starry_night: magic levels
	@echo For a starry night, open ${OUTPUT}\!

levels: blur
	@${MAGIC} ${OUTPUT} -level ${COW} ${OUTPUT}

blur: noise
	@${MAGIC} ${OUTPUT} -blur ${HOW_BLURRY} ${OUTPUT}

noise: black
	@${MAGIC} ${OUTPUT} -evaluate Gaussian-noise ${HOW_STARRY} ${OUTPUT}

black:
	@${MAGIC} -size ${SIZE} xc:black ${OUTPUT}

magic:
	@which ${MAGIC} >/dev/null || (echo "Please install ImageMagick on your system. Thank you."; exit 1)