Create center cropped thumbnail images

Makefile

# Create thumbnails in another directory.  Center resize and crop
# images to 150x150.

OBJDIR := ../tabs-square
IMG_SRC := $(wildcard *.jpg)
OBJS := $(addprefix $(OBJDIR)/,$(IMG_SRC))

$(OBJDIR)/%.jpg : %.jpg
	convert \
		$< \
		-resize 150 \
		-gravity center \
		-crop 150x150+0+0 \
		$@

all : $(OBJS)

$(OBJS) : | $(OBJDIR)

$(OBJDIR) :
	mkdir $(OBJDIR)

.PHONY : clean
clean:
	rm -f $(OBJDIR)/*.jpg

.PHONY : variables
variables:
	@echo Sources: $(IMG_SRC)
	@echo Target Directory: $(OBJDIR)
	@echo Targets: $(OBJS)