Image Manipulation

In “Advanced Techniques,” Listing 11-13 shows how to resize an image using osascript.

In addition to the osascript interface, Mac OS X includes the sips command, which provides a direct shell interface to some of the image processing features in Mac OS X.

The following snippet shows how to use sips to scale an image to a maximum of 250 pixels horizontally or vertically and convert the image to JPEG format.

sips -s format jpeg --resampleHeightWidthMax 250 myphoto.tif --out mythumb.jpg

You can also combine sips with exiftool (available from http://www.sno.phy.queensu.ca/~phil/exiftool/) for even greater power and control. The following script uses sips and exiftool to automatically rotate a photograph based on the encoded orientation information, and allows you to specify an offset (in 90 degree increments) to adjust the rotation further.

Listing C-6  Rotating an image using sips

#!/bin/sh

# Adjust paths as needed

EXIFTOOL=/usr/local/bin/exiftool

SIPS=/usr/bin/sips

INPUTFILE="$1"

OUTPUTFILE="$2"

OFFSET="$3"

# If the user doesn't specify an offset, assume zero.

if [ "$OFFSET" = "" ] ; then

OFFSET=0

fi

# Use exiftool to read the EXIF orientation tag as a raw numeric value.

ORIENTATION="$($EXIFTOOL -b -Orientation $INPUTFILE)"

# If no orientation tag is found, assume no rotation is needed.

if [ "$ORIENTATION" = "" ] ; then

ORIENTATION=1

fi

# This table determines the rotation (in 90 degree increments)

# based on the EXIF orientation tag and determines whether a

# coordinate transformation is needed.

case $ORIENTATION in

(1) ROT=0; FLIP=0;; # No rotation or flip needed.

(2) ROT=0; FLIP=1;; # Flip horizontal.

(3) ROT=2; FLIP=0;; # Rotate 180, no flip.

(4) ROT=2; FLIP=1;; # Rotate 180, flip.

(5) ROT=3; FLIP=1;; # Rotate 270, flip.

(6) ROT=1; FLIP=0;; # Rotate 90, no flip.

(7) ROT=1; FLIP=1;; # Rotate 90, flip.

(8) ROT=3; FLIP=0;; # Rotate 270, no flip.

(*) echo "BAD ORIENTATION $ORIENTATION" ; exit -1;;

esac

# Calculate the number of degrees to rotate the image

# based on the above table and the user-entered adjustment.

DEGREES="$(expr 90 '*' '(' $OFFSET '+' $ROT ')')"

# Generate the additional flags for sips if flipping is required.

FLIPSTR=""

if [ $FLIP = 1 ] ; then

FLIPSTR="--flip horizontal"

else

FLIPSTR=""

fi

# Perform the transformation.

$SIPS $FLIPSTR --rotate $DEGREES $INPUTFILE --out $OUTPUTFILE

# Delete the orientation keys so that sips and other tools

# won't get confused when doing auto-rotation.

$EXIFTOOL -Orientation= $OUTPUTFILE

SIPS についての資料は少ない。
Apple 本家 Mac Dev Center の資料。
例題の Shell Script もわかりやすい。