makefile: Add image comparison targets

Add the `make compare`, `make update` targets to the Makefile
(lifted from `Makefile.old`)

Signed-off-by: Christophe de Dinechin <christophe@dinechin.org>

Author: c3d

Makefile

@@ -434,6 +434,30 @@ $(CHUCK_GIT_H):
 	@mkdir -p $(@D)
 	$(PRINT_GENERATE) tools/generate-chuck.sh > $@
 
+#------------------------------------------------------------------------------
+#  Image comparison
+#------------------------------------------------------------------------------
+
+IMAGES=$(COLOR:%=color-)images
+cmp-% compare-%:
+	compare $(IMAGES)/$*.png $(IMAGES)/bad/$*.png -compose src $*.png || true
+	open $*.png $(IMAGES)/bad/$*.png $(IMAGES)/$*.png
+	echo mv -f $(IMAGES)/bad/$*.png $(IMAGES)/$*.png
+update-%:
+	mv $(IMAGES)/bad/$*.png $(IMAGES)/$*.png
+	rm -f $*.png
+updates-%:
+	$(MAKE) update-$* color-update-$*
+cmps-% compares-%:
+	$(MAKE) compare-$* color-compare-$*
+
+BAD_IMAGES=$(wildcard $(IMAGES)/bad/*.png)
+compare: $(BAD_IMAGES:$(IMAGES)/bad/%.png=cmp-%)
+update: $(BAD_IMAGES:$(IMAGES)/bad/%.png=update-%)
+updates: update color-update
+compares: compare color-compare
+.PHONY: compare update
+
 # ------------------------------------------------------------------------------
 # Help generation (lifted from Makefile)
 # ------------------------------------------------------------------------------