Re: [Lcms-user] need advice on adding cms to an image viewer

[Kai-Uwe B. <ku...@gm...>]

Am 30.07.06, 15:50 -0500 schrieb Paul Miller:

> Kai-Uwe Behrmann wrote:
> >> Do I need to do a transform on LOAD to get the image into some common 
> >> working space (like sRGB), then another transform at display time to 
> >> integrate the desired output profile? If the image contains an ICC 
> >> profile, should I transform from that profile to the "working" profile? 
> >> What happens if there is no embedded profile?
> > 
> > The behaviour depends on the user settings in the colour management system 
> > of the OS. On osX beeing it ColorSync for Windows ICM. For Linux / BSD 
> > there is still nothing distributed by default. For the later you could 
> > implement yourself a dialog allowing users to do the settings.
> 
> Lets say I load a JPEG with an embedded profile. Do I transform FROM 
> that profile to another one before I do any manipulation to the image, 
> or is it safe to leave the data "as is" read from the file until I'm 
> ready to DISPLAY the image, then transform from the JPEG's profile to 
> the user-selected profile (ie. Adobe sRGB, Apple RGB, ColorMatch, etc)?

A editor/viewer would leave the numbers as is, until a manipulation is 
wanted. This would be a nice feature.

Then ask the system (OS level color management, not lcms) if 
  the user opted to to work on any colour space -> leave the numbers,
  the user opted to convert to editing (working) space -> check for 
  difference of image colour space to editing colour space -> convert to 
  editing colour space
  the user opted to been queried -> promt for profile selection

The old or new image profile and the display profile are used to 
transform colours from the image buffer into the display buffer.

> The same goes for a JPEG WITHOUT an embedded profile. How/when does it 
> get transformed? Do I just create a "null" transform for it?

Select the user prefered default profile.

> I've already written code to extract an embedded profile from a JPEG, 
> and I have a menu for selecting the desired display profile. I just need 
> to know where to do the actual transform.
> 
> -- 
> Paul Miller | pa...@fx... | www.fxtech.com | Got Tivo?

Look at applications like Adobe CS, Scribus or CinePaint how they 
behave and design the dialogs. Later provide source code.

regards
Kai-Uwe Behrmann
                                + development for color management 
                                + imaging / panoramas
                                + email: ku...@gm...
                                + http://www.behrmann.name