Can I convert an image from CMYK to RGB in Mac OS X?

Question

Is there a way to convert a JPEG from CMYK to RGB, using Preview or any other tool built into Mac OS X?

I see I can go to Tools | Assign Profile… and select from a long list of options, including Generic CMYK Profile, but there's no RGB option.

Answer 1

I found three ways to do it.

1. Open the image with ColorSync.
2. Use the Apply ColorSync Profile to Images action in Automator.
3. Use sips (thanks NSD) and supply the --matchTo argument. I wrote a shell script to convert an image using the Generic RGB Profile.

 

#!/bin/sh

if [ $# -lt 1 ]; then
    cat >&2 <<EOF
usage:
    $0 filename
    $0 source-file destination-file

    Converts an image to RGB color space. The first form manipulates
    the file in-place.
EOF
    exit 1
fi           

SOURCE_FILE=$1

if [ $# -lt 2 ]; then
    DESTINATION_FILE=$SOURCE_FILE
else
    DESTINATION_FILE=$2
fi

sips \
    --matchTo '/System/Library/ColorSync/Profiles/Generic RGB Profile.icc' \
    "$SOURCE_FILE" \
    --out "$DESTINATION_FILE"

Answer 2

On my machine (10.6.2), two RGB profiles are offered: "Adobe RGC (1998)" and "Generic RGB Profile". Gimp (free) can do the conversion, too.

Answer 3

http://developer.apple.com/Mac/library/documentation/Darwin/Reference/ManPages/man1/sips.1.html

Answer 4

I didn't have the RGB colorsync profiles, so I imported the files into iPhoto and then exported them again. The exported photos were in RGB. Voila

Answer 5

It's really easy. You don’t need to do any of these steps. In the Mac OS X “Preview” app, just go under Tools, Match to Profile, and under “Color Model” select RGB. The ColorSync Profile will change automatically. Save, and it’s done!

Answer 6

For whatever reason I wasn't able to change the color mode with Preview and the Tools section. My needs my have been simpler, but I ended up just opening the image in Preview on my large external monitor and then using Skitch to take a screenshot of it. It fit my needs, it may fit yours.

Answer 7

If you have ImageMagick installed on your machine, you can do this in Terminal.

For image.jpg:

convert -colorspace RGB image.jpg newImage.jpg

newImage.jpg will be the same image in RGB space.