# Checks existence of necessary executables
CONVERT:=$(shell command -v convert 2> /dev/null)
XELATEX:=$(shell command -v xelatex 2> /dev/null)
PDFTOPPM:=$(shell command -v pdftoppm 2> /dev/null)
PDFUNITE:=$(shell command -v pdfunite 2> /dev/null)

ifndef CONVERT
	$(error "convert not found. Please install imagemagick")
endif
ifndef XELATEX
	$(error "xelatex not found. Please install xetex")
endif
ifndef PDFTOPPM
	$(error "pdftoppm not found. Please install poppler")
endif
ifndef PDFUNITE
	$(error "pdfunite not found. Please install poppler")
endif