Re: `Lossless' retroactive embedding of color profile (avoid JPEG recompression); basic color profile theory
Re: `Lossless' retroactive embedding of color profile (avoid JPEG recompression); basic color profile theory
- Subject: Re: `Lossless' retroactive embedding of color profile (avoid JPEG recompression); basic color profile theory
- From: John Gnaegy <email@hidden>
- Date: Tue, 1 Aug 2006 14:31:13 -0700
I wish to associate (embed) a profile to these files afterwards.
You can use sips. The following will embed Generic RGB Profile into
all the images inside a folder called "stuff" on my desktop.
sips -e /System/Library/ColorSync/Profiles/Generic\ RGB\ Profile.icc /
Volumes/hd/john/Desktop/stuff/*
Note the "\ " in Generic RGB Profile, you have to use that for any
file or folder name with a space in it. Instead of using "\ ", you
could instead put the whole path in quotes like this:
sips -e "/System/Library/ColorSync/Profiles/Generic RGB Profile.icc" /
Volumes/hd/john/Desktop/stuff/*
Instead of sips, you could use /Library/ColorSync/Scripts/Embed
Chosen Profile.
In other words: Do you think that the raw data in an image without
a profile and in the same (hypethetical) one with a profile would
be the same, except for the added colour profile?
Yes the image data is the same, the only difference is the embedded
profile. You can embed or remove a profile from an image as many
times as you like without affecting the original image data.
which profile should I chose?
For images created on cameras or scanners, the profile that most
accurately describes the color space of the device on which the image
was created. So if it's a camera, ideally you'd want to embed a
profile of that camera.
For images you're editing in Photoshop, you should embed Photoshop's
working space, since for all intents and purposes that's the color
space of the device on which you're editing the image.
So the question is, how accurately does Adobe RGB or sRGB represent
that Minolta camera? That's hard to tell. Lacking a profile built
for that camera, you could try embedding one, then the other, or even
Apple's Generic RGB or Camera RGB and seeing which looks best. It's
not ideal, but anything short of building a profile for the camera is
less than ideal, so it's worth trying.
You can save yourself some time in this experimental stage by using
Photoshop or Preview to try different source profiles, both apps
allow you to designate the source profile of an image. Open an image
in Photoshop and on the first dialog that appears choose "Discard
profile" so you're looking at the original unmatched image data, then
from the menubar choose Image - Mode - Assign Profile. In Preview
open an image and from the menubar choose Tools - Assign Profile.
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