Makefile for images. Cleanup.

Makefile

@@ -1,11 +1,26 @@
+.DEFAULT_GOAL := build
 
-all: images download
+SRC_IMAGES := $(wildcard gallery/*.jpg)
+DST_IMAGES := $(sort $(addprefix build/,$(addsuffix .bmp,$(notdir $(basename $(SRC_IMAGES))))))
+
+all: clean build
 
-images:
-	cd gallery && for F in *.jpg; do ./convert_image.sh $F $F.bmp
-	
 download: jokes.json
 
-jokes.json:
-	curl -o jokes.json https://github.com/wiz64/superfun/raw/main/database/ichd/jokes-file.json
+jokes.json: build-dir
+	curl -o build/jokes.json https://github.com/wiz64/superfun/raw/main/database/ichd/jokes-file.json
+
+build: build-dir images download
+
+build-dir:
+	mkdir -p build
+
+images: $(DST_IMAGES)
+
+$(DST_IMAGES): build/%.bmp: gallery/%.jpg
+	./convert_image.sh $< $@
+
+.PHONY: clean
+clean:
+	rm -rf build/