This document discusses using makefiles to automate image processing tasks like scaling large sets of images. It presents a problem of needing to repeatedly scale images when target resolutions change. The proposed solution is to use NetPBM image tools and GNU make, which is well-suited for automating transformations from input to output files according to rules. An example makefile is provided that uses find, patsubst and shell commands to scale images in a source directory to a target resolution and save them in a scaled directory.

1. Makefiles for
Automating
Image Processing
Shweta Sadawarte
CEO Nelkinda Software Craft Pvt Ltd

2. Problem
● Scale a large set (200+) of images to a
target resolution.
● Target resolution might change due to
website redesign -> scaling has to be
repeated
● Image set might change - new images might
be added later.

3. Solution
● Automatable image processing using
NetPBM
● Automation using GNU make

4. Why to use make?
● Having a set of input files that shall be
transformed to a set of output files according
to certain rules is the nature of make.
● The make program uses timestamp to
decide which of the files need to be updated.

5. SRC_FILES:=$(shell find source/ -name "*.jpg")
SCALED_FILES:=$(patsubst source/%.jpg, scaled/%.jpg, $(SRC_FILES))
.PHONY: all
all: scale
.PRECIOUS: %/
%/:
mkdir -p $@
.PHONY: clean
clean:
$(RM) -r scaled
.PHONY: scale
scale: $(SCALED_FILES)
scaled/%.jpg: source/%.jpg | scaled/
< $< jpegtopnm | pnmscale -xysize 1280 962.4 | pnmtojpeg --quality 85
--progressive > $@

6. ● https://www.facebook.com/creazione4u/