In this day and age this should be trivial an easy. But to do it right is still not widely known. Applications like Adobe Lightroom can optionally do output sharpening (which I think is a desirable feature). But since I’ve abandoned Adobe products, I’m left to my own devices. So my solution to this was a Makefile and ImageMagick. My script is based on a tutorial called Sharpening using ImageMagick.Here is the Makefile:

# Make thumbnail, small, medium and large images sharpened and compressed
# correctly for wordpress.
#
# Instructions taken from:
# http://redskiesatnight.com/2005/04/06/sharpening-using-image-magick/

CONVERT=/sw/bin/convert
THUMB_SIZE=160x160
SMALL_SIZE=320x320
MEDIUM_SIZE=640x640
LARGE_SIZE=1280x1280
QUALITY=80

# unsharp mask settings...
# radius = output ppi / 150
RADIUS=0.667
# if radius < 1, then sigma = radius
# else sigma = sqrt(radius)
SIGMA=0.667
# -unsharp <radius>{x<sigma>}{+<amount>}{+<threshold>}
UNSHARP=$(RADIUS)x$(SIGMA)+0.5+0.07

SOURCES=aftermath.jpg bumble-bee.jpg cochise.jpg gladstone-cow.jpg nuclear-flowers.jpg walk.jpg whitianga-beach.jpg
THUMB_FILES=$(SOURCES:.jpg=-t.jpg)
SMALL_FILES=$(SOURCES:.jpg=-s.jpg)
MEDIUM_FILES=$(SOURCES:.jpg=-m.jpg)
LARGE_FILES=$(SOURCES:.jpg=-l.jpg)
OUTPUTS=$(THUMB_FILES) $(SMALL_FILES) $(MEDIUM_FILES) $(LARGE_FILES)

help:
 @echo "Create resized images for:"
 @echo " $(SOURCES)"
 @echo
 @echo "Use 'make all' to generate all images"

all: $(OUTPUTS)
thumb: $(THUMB_FILES)
small: $(SMALL_FILES)
medium: $(MEDIUM_FILES)
large: $(LARGE_FILES)

clean:
 rm -f $(THUMB_FILES)
 rm -f $(SMALL_FILES)
 rm -f $(MEDIUM_FILES)
 rm -f $(LARGE_FILES)

%-t.jpg: %.jpg
 $(CONVERT) -resize $(THUMB_SIZE) $< -unsharp $(UNSHARP) -quality $(QUALITY) $@

%-s.jpg: %.jpg
 $(CONVERT) -resize $(SMALL_SIZE) $< -unsharp $(UNSHARP) -quality $(QUALITY) $@

%-m.jpg: %.jpg
 $(CONVERT) -resize $(MEDIUM_SIZE) $< -unsharp $(UNSHARP) -quality $(QUALITY) $@

%-l.jpg: %.jpg
 $(CONVERT) -resize $(LARGE_SIZE) $< -unsharp $(UNSHARP) -quality $(QUALITY) $@