Re: [Lcms-user] Apply profile with PCS = cmsSigXYZData, Color Space = cmsSigGrayData

[Aaron B. <bo...@gm...>]

Noel, do you know where I could find sample code to read/write ICC profiles
for PNG format?

Thanks,
Aaron

On Mon, Feb 20, 2017 at 12:20 PM, Noel Carboni <
NCa...@pr...> wrote:

> > For other formats, such as PNG, I would need to transform.
>
>
>
> I believe a PNG file can carry a color profile tag, but there are
> certainly formats that can't.
>
>
>
> Not to belabor this, but does your design specify what color space the
> data will be in if it saved in an image file format that does not carry a
> profile tag?
>
>
>
> There is no standard for what color space untagged images should be stored
> in.  Because of the mix of computers in the world and the things that have
> been done in the past, you might meet expectations more of the time if you
> were save color images in the sRGB IEC61966-2.1 color space.  Windows has
> been described as embracing "sRGB by default", for example.  But that's up
> to you.
>
>
>
> If you are anticipating prompting the user for target color space
> information, then that could resolve the problem.
>
>
>
> -Noel
>
>
>
> *From:* Aaron Boxer [mailto:bo...@gm...]
> *Sent:* Mon, February 20, 2017 12:02 PM
> *To:* Noel Carboni
> *Cc:* lcm...@li...
> *Subject:* Re: [Lcms-user] Apply profile with PCS = cmsSigXYZData, Color
> Space = cmsSigGrayData
>
>
>
> Thanks, Noel. That is a good point. For TIFF, I can store the profile in
> the TIFF file, and avoid transforming.
>
> For other formats, such as PNG, I would need to transform.
>
>
>
> On Mon, Feb 20, 2017 at 11:49 AM, Noel Carboni <
> NCa...@pr...> wrote:
>
> > Thanks, Noel. This is not for display on monitor. JPEG 2000 supports
> embedded ICC profiles, and I am
>
> > trying to use the profile when decoding the image.
>
>
>
> I guess I'm still not clear:  Why are you transforming the data into
> another color space?
>
>
>
> If you're trying to decode it then save it as another kind of file (e.g.,
> .tiff or .jpg or something that can carry its own color profile tag), maybe
> you should consider just maintaining the color profile it's already got.
>
>
>
> What I'm saying is that maybe you just want to decode the data, then save
> the data in another file, and tag that file with the same profile the
> JPEG2000 file started with, making no color transformation on the decoded
> data at all.  LittleCMS need not be involved with that.
>
>
>
> As Marti mentioned, if you DO want to transform the color values into a
> different color space, you need to specify what that color space is.
>
>
>
> -Noel
>
>
>
>
>